Geopolymers are an alternative to Portland cement, well known for their contribution to greenhouse gas emissions. Finding materials that can validly replace Portland cement is a challenge. It is in this logic that thi...Geopolymers are an alternative to Portland cement, well known for their contribution to greenhouse gas emissions. Finding materials that can validly replace Portland cement is a challenge. It is in this logic that this work was undertaken with the objective of characterizing two local clay resources of Togo as raw materials for geopolymers. The physico-chemical properties of these clays were determined by characterization using X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric (TGA) and elemental analysis (ICP-OES). The results show that these clays contain kaolinite and therefore can be used in the formulation of geopolymers. The characterized clays underwent heat treatments transforming the crystalline phases into more reactive amorphous phases and then were activated by an alkaline solution in order to formulate the geopolymer materials. These elaborated materials were analyzed by Fourier transform infrared to identify the types of bonds formed. The results of these analyses show that these two local clays are well suited to be used in synthesizing geopolymers. Our future work will focus on the constraints of consolidation as well as the mechanical properties of these geopolymer materials.展开更多
In the framework of various phosphates discharges valorization, we have realized physicochemical and mineralogical characterizations of these discharges. We have undertaken the physicochemical and mineralogical charac...In the framework of various phosphates discharges valorization, we have realized physicochemical and mineralogical characterizations of these discharges. We have undertaken the physicochemical and mineralogical characterizations of this waste by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), thermal analysis and Atomic Emission Spectrometry Coupled to an Inductive Plasma Source. The results of these analyze show that phosphate sludge and screen rejects could be used in ceramics, in the manufacture of aggregates, in agriculture and other fields. On the other hand, rich magnetic waste could be used in heterogeneous photocatalysis in waste liquids treatment.展开更多
In C ?te d’Ivoire, traditional ceramics are widely used in the form of pottery. The latter is used to store food, water and cereals. Analyzes (X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ...In C ?te d’Ivoire, traditional ceramics are widely used in the form of pottery. The latter is used to store food, water and cereals. Analyzes (X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductive plasma optical emission spectrometry (ICP-OES), scanning electron microscopy (SEM) and analysis thermal gravimetric (ATG)) were carried out to determine the morphology, the chemical, physical and pedological constituents of these raw materials. It appears from this study that the clays used in the Mangoro pottery of Katiola contain silica SiO<sub>2</sub>, alumina Al<sub>2</sub>O<sub>3</sub> and iron oxide Fe<sub>2</sub>O<sub>3</sub> as well as kaolinite, muscovite, smectite and quartz.展开更多
The objective of this study is to develop carbon, that of <i></span><i><span style="font-family:Verdana;">Acacia auriculeaformis</span></i><span style="font-family...The objective of this study is to develop carbon, that of <i></span><i><span style="font-family:Verdana;">Acacia auriculeaformis</span></i><span style="font-family:Verdana;"></i></span><span style="font-family:Verdana;"> through its activation in order to eliminate lead in an aqueous medium. A series of activated carbon has been prepared by chemical activation with phosphoric acid, sodium hydroxide and sodium chloride. The determi</span><span style="font-family:Verdana;">nation of the physico-chemical properties of the prepared carbon guided the choice of phosphoric acid activated carbon as the best adsorbent for the</span><span style="font-family:Verdana;"> elimination of lead(II) in </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">an </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">aqueous solution. Pb</span><sup><span style="font-family:Verdana;">2+</span></sup><span style="font-family:Verdana;"> adsorption tests in batch mode have shown that the adsorption capacity is influenced by various parameters such as mass, pH, concentration of Pb<sup>2+</sup> ions and contact time linked to the medium and the adsorbent. Adsorption isotherms, kinetic models and thermodynamics have been used to describe the adsorption process. The equilibrium data for activated charcoal correspond well to the model of Freundlich, </span><span style="font-family:Verdana;">Langmuir, Temkin and Kiselev. The kinetic adsorption data proved to be </span><span style="font-family:Verdana;">better described by the pseudo-second order model with </span><span style="font-family:Verdana;">external and intraparticle diffusion which are two decisive steps in the</span><span style="font-family:Verdana;"> adsorption process of Pb<sup>2+</sup> ions. Thermodynamics and adsorption isotherms predict a spontaneous exothermic surface reaction, of the chemisorption type, with ion </span><span><span style="font-family:Verdana;">retention in orderly monolayers on the heterogeneous surface of the adsorbent. Tests carried out with this adsorbent material have contributed to the elimination of the Pb</span><sup><span style="font-family:Verdana;">2+</span></sup><span style="font-family:Verdana;"> ions contained in an industrial effluent with a </span></span><span style="font-family:Verdana;">reduction rate reaching 42.52% against 85.90% in a synthetic solution.展开更多
Highly hydrophobic Di 2-ethyl hexyl phthalate（DEHP） is one of the most prevalent plasticizers in wastewaters. Since its half-life in biological treatment is around 25 days, it can be used as an efficiency indicator ...Highly hydrophobic Di 2-ethyl hexyl phthalate（DEHP） is one of the most prevalent plasticizers in wastewaters. Since its half-life in biological treatment is around 25 days, it can be used as an efficiency indicator of wastewater treatment plant for the removal of hydrophobic emerging contaminants. In this study, the performance of submerged membrane bioreactor was monitored to understand the effect of DEHP on the growth of aerobic microorganisms. The data showed that the chemical oxygen demand（COD）and ammonia concentration were detected below 10 and 1.0 mg/L, respectively for operating conditions of hydraulic retention time（HRT） = 4 and 6 hr, sludge retention time（SRT） = 140 day and sludge concentration between 11.5 and 15.8 g volatile solid（VS）/L. The removal efficiency of DEHP under these conditions was higher and ranged between 91% and 98%. Results also showed that the removal efficiency of DEHP in biological treatment depended on the concentration of sludge, as adsorption is the main mechanism of its removal. For the submerged membrane bioreactor, the pore size is the pivotal factor for DEHP removal, since it determines the amount of soluble microbial products coming out of the process. Highly assimilated microorganisms increase the biodegradation rate, as 74% of inlet DEHP was biodegraded; however, the concentration of DEHP inside sludge was beyond the discharge limit. Understanding the fate of DEHP in membrane bioreactor,which is one of the most promising and futuristic treatment process could provide replacement for conventional processes to satisfy the future stricter regulations on emerging contaminants.展开更多
The objective of this work is to prepare one of the best activated carbon (CA) based on wood (Acacia auriculeaformis). The chemical activation method was used for varying the chemical agent namely phosphoric acid H3PO...The objective of this work is to prepare one of the best activated carbon (CA) based on wood (Acacia auriculeaformis). The chemical activation method was used for varying the chemical agent namely phosphoric acid H3PO4 (CAA), sodium hydroxide NaOH (CAB), and sodium chloride NaCl (CAS). The physico-chemical analysis of the three activated carbons indicated that, under the conditions of preparation, the activated carbons possess activation efficiencies lower than 50% (41.81% for CAA, 26.25% for CAB and 48.87% for CAS), low ash content (CAA: 5.00%, CAB: 14.90 and CAS: 6.60%) and iodine values ranging from 190.35 mg/g to 380.71 mg/g, suggesting that the good quality of the prepared activated carbon. The surface functional groups using Boehm test and the zero point charge (pHZPC) methods confirmed the acidic, basic and neutral character for CAA, CAB and CAS respectively (CAA: pHZPC = 4.8, CAB: pHZPC = 8.2, CAS: pHZPC = 6.8). The surface specific areas were determined through the liquid phase adsorption of acetic acid and methylene blue using the Langmuir method and BET analysis. Also, the porosity was determined. The BET surface areas of CAA, CAB and CAS were respectively 561.60 m2/g, 265.00 m2/g and 395.40 m2/g. The influence of chemical activation agent on pores formation was confirmed by scanning electron microscopic (SEM) analysis. CAA was selected as the best activated carbon because of its good surface area and good pore volume compared to those found in the literature. Therefore, its application as an adsorbent for effluents treatment could be explored. In addition, the best activating agent for coal from Acacia auriculeaformis was found to be phosphoric acid.展开更多
In this work, low cost coconut biochar based activated carbon (CBAC) was used for adsorption of Butylparaben (BPB) from aqueous medium. The prepared CBAC was characterized using BET, Boehm analysis and the adsorption ...In this work, low cost coconut biochar based activated carbon (CBAC) was used for adsorption of Butylparaben (BPB) from aqueous medium. The prepared CBAC was characterized using BET, Boehm analysis and the adsorption equilibrium, kinetics and thermodynamics studies of BPB adsorption were carried out. During batch adsorption runs, the effects of factors, such as contact time (0 - 300 min), CBAC dose (200 - 800 mg), pH (3 - 11) and solution temperatures (303 - 348 K) were investigated on BPB removal. Experimental results reveal that the BPB removal efficiency on CBAC is higher than 97% under acidic and neutral conditions. Equilibrium data were fitted by Langmuir, Freundlich and Temkin isotherm models with correlation coefficient more than 0.9. The pseudo-second order kinetic model was observed to fit well the adsorption data. Thermodynamic analysis shows positive values of standard Gibb’s free energy, suggesting the non-spontaneity of the process. The changes in enthalpy (0.2 J.mol-1) and entropy (19 J.mol-1) were found to be endothermic with an increase of randomness. The high adsorption efficiency of the synthesized coconut biochar materials with low cost indicates that it may be a promising adsorbent for removing organic compounds.展开更多
Photocatalytic degradation of paraquat (PQ) aqueous solutions was studied in a fixed bed photoreactor under UV irradiation at 368 nm. This contained β-SiC alveolar foams coated with TiO2 P25 by dip-coating method. SE...Photocatalytic degradation of paraquat (PQ) aqueous solutions was studied in a fixed bed photoreactor under UV irradiation at 368 nm. This contained β-SiC alveolar foams coated with TiO2 P25 by dip-coating method. SEM analyses revealed that the surface of the film did not exhibit cracks in the presence of TTIP as a binder in the TiO2 P25 suspension. The following parameters were studied in continuous mode operation: the flow rate in the reactor, the initial concentration of the paraquat, the pH of the solution, the weight of photocatalytic material with the number of foams in the reactor and the weight of the catalyst deposited onto the support. The results showed that by working under optimal operating conditions at natural pH (pH = 6.7), low paraquat (Co = 10 ppm), and flow (26 mL/min), we recorded approximately (43.16 ± 1.00)% oxidation of paraquat and a decrease in total organic carbon (TOC) of (27.13 ± 1.00)% after about 70 minutes. The apparent rate constant is in the order of (0.0656 ± 0.0010) min-1. In addition, by increasing the amount of β-SiC foams coated with TiO2, we improve the degradation of paraquat in the same order. The study of aging of the material showed its stability over time. However, photocatalytic activity was limited after 20 minutes of UV irradiation due to the limitation of the diffusion of the paraquat molecules towards the surface of the photocatalyst. As an outcome, we obtained an efficient TiO2/β-SiC material for photocatalytic degradation of organic compounds in water.展开更多
The development of biofuels is driven both by concern about the greenhouse effect and by interest in the opportunities for exploitation of biomass of agricultural origin. In order to improve the yield and quality of b...The development of biofuels is driven both by concern about the greenhouse effect and by interest in the opportunities for exploitation of biomass of agricultural origin. In order to improve the yield and quality of biodiesel through modeling and optimization, several studies are in progress. In this paper, biodiesel produced from rubber seed oil in the homogeneous transesterification is studied using a Plackett-Burman experimental design, a full factorial design, a central composite design and an Artificial Neural Network (ANN) coupled with a Genetic Algorithm (GA).Variables such as temperature, stirring speed, reaction time, type of alcohol, and type of catalyst are studied to obtain the best specific gravity and kinematic viscosity. Type of alcohol and type of catalyst have the greatest effect on the two responses, with ethanol (alcohol) and sulphuric acid (catalyst) producing the best results. The specific gravity and kinematic viscosity changes recorded during the transesterification process followed the first and second order polynomial models, respectively. The ANN coupled with GA was used to optimize the two responses simultaneously. Global optimal values of specific gravity (0.883) and kinematic viscosity (6.76 cSt) were recorded when a temperature of 90°C, a stirring speed of 305 rpm, and a treatment time of 141 min were imposed.展开更多
The environmental problems caused by plastics of fossil origin are well known. To reduce harmful impact on the environment, bacterial-based plastics, such as polyhydroxyalkanoates (PHAs), are a promising solution. Mic...The environmental problems caused by plastics of fossil origin are well known. To reduce harmful impact on the environment, bacterial-based plastics, such as polyhydroxyalkanoates (PHAs), are a promising solution. Microbial PHAs can be produced using abundant and inexpensive agricultural by-products as raw material. In this study, the potential use of Cupriavidus necator 11599 for the bioconversion of cassava starch into biodegradable PHAs was explored. Although Cupriavidus necator 11599 is a well-known PHA producer, it cannot grow directly on starch. Thus, acid hydrolysis was carried out on the starch extracted from cassava peels to obtain fermentable sugars. Optimal concentration of reducing sugars (RSs) was obtained by hydrolysis of cassava peel starch with sulfuric acid concentrations of 0.4 N and 0.6 N, at 95˚C and 4 h. The hydrolyzed starch was used for PHA production in Erlenmeyer flasks using reducing sugars (RSs) concentrations ranging from 10 g/L to 25 g/L. The best RS concentration 20 g/L and 25 g/L gave 85.13% ± 1.17% and 89.01% ± 2.49% of biomass PHA content and biomass concentrations of 8.18 g/L and 8.32 g/L, respectively in 48 hours. This research demonstrates that cassava peel starch as an inexpensive feedstock could be used for PHA production, paving the way for the use of other starchy materials to make bioplastics.展开更多
In the present study,municipal secondary sludge and purified glycerol(obtained after acid treatment of crude glycerol)were used together for lipid production using intermittent feeding strategy.Intermittent sludge fee...In the present study,municipal secondary sludge and purified glycerol(obtained after acid treatment of crude glycerol)were used together for lipid production using intermittent feeding strategy.Intermittent sludge feeding strategy(sludge SS 30 g/L)resulted in a higher biomass(54.99 g/L)and lipid concentration(25.35 g/L)at 96 h when compared to 35 g/L SS single sludge feeding or control strategy(45.67 g/L biomass&19.16 g/L lipid).Moreover,the intermittent sludge feeding strategy significantly reduced foaming and requirement of anti-foam during fermentation when compared to control strategy.The energy balance of biodiesel production from lipid obtained by intermittent sludge feeding strategy(30 g/L SS)was energeti-cally favorable.It was also revealed from yield coefficients and energy balance that sludge had an important contribution in microbial lipid and biodiesel production.展开更多
Purified glycerol obtained after acid treatment of crude glycerol solution was used as the carbon source for lipid and citric acid production using Y.lipolytica SKY7.Although purified glycerol was high in phosphorus,i...Purified glycerol obtained after acid treatment of crude glycerol solution was used as the carbon source for lipid and citric acid production using Y.lipolytica SKY7.Although purified glycerol was high in phosphorus,it was important to inves-tigate the impact of fortification of trace elements in the medium on cell growth,lipid and citric acid(CA)production.When all the trace elements(including phosphates and sulfates)required for growth and lipid production were added to the purified glycerol medium,high biomass(51.67 g/L)and lipid concentration(19.47 g/L)were observed at 96 h of fed-batch fermentation with low CA concentration of 5.42 g/L.The purified glycerol medium without additional trace elements gave low biomass(27.67 g/L),lipid concentration(9.35 g/L)at 80 h of fed-batch fermentation,but gave high CA concentration(24.51 g/L).When purified glycerol was provided with only sulfates or all elements except KH_(2)PO_(4),low biomass(32.59 g/L and 38.52 g/L)and citric acid concentration(1 g/L and 2.42 g/L)were obtained at 96 h.展开更多
The study was conducted to investigate the effect of sludge retention on bacterial community composition of membrane bioreactor(MBR)treating synthetic hospital wastewater.The removal of four pharmaceuticals,namely car...The study was conducted to investigate the effect of sludge retention on bacterial community composition of membrane bioreactor(MBR)treating synthetic hospital wastewater.The removal of four pharmaceuticals,namely carbamazepine,estradiol,venlafaxine,and ibuprofen in MBR,was studied at varying sludge retention time(SRT)duration of 100,45,and 15 days and hydraulic retention time(HRT)of 18 h.The removal of ibuprofen and estradiol was constant at varying SRT;however,a negligible removal of carbamazepine and low removal of venlafaxine was observed(<20%).The study suggested that the SRT of 45 days in MBR could provide maximum treatment efficiency via decreasing membrane clogging.The effect of sludge age and pharmaceutical presence on the bacterial community was investigated via high-throughput sequencing.The study reveals that the variation in SRT affects the dynamics of the bacterial community significantly.For instance,the dominant bacterium Caldimonas of SRT 100 was disappeared at lower SRTs.Moreover,the profile of the dominant genus of the SRTs varied greatly from each other.展开更多
Extracellular polymeric substances(EPSs)play a crucial role in various applications,especially in wastewater treatment.This review explores the importance of EPS in modern treatment methods,emphasizing its organic pol...Extracellular polymeric substances(EPSs)play a crucial role in various applications,especially in wastewater treatment.This review explores the importance of EPS in modern treatment methods,emphasizing its organic polymeric nature and properties that aid in effective pollutant removal and resource conservation.The study focuses on biological strategies utilizing microbial and bacterial communities,as well as electrolyte precipitate systems containing various components such as uronic acids,proteins,and carbohydrates that are essential for treatment processes.This review also describes the complex mechanisms regulating EPS biosynthesis,highlighting the impact of factors such as temperature,light intensity,and carbon to nitrogen ratio on EPS production.These findings emphasizes the influence of carbon supply and nitrogen sources on EPS formation,shedding light on the relationship between environmental conditions and EPS synthesis.In addition,this study discusses the significance of EPS extraction techniques for maintaining material integrity.Furthermore,the review explores the broad applications of EPS beyond wastewater treatment,including soil aggregation,pharmaceuticals,the food industry,and sustainable energy generation through EPS-driven microbial fuel cells.Understanding the diverse functions of EPS has the potential to improve environmental practices,mitigate climate change effects,and enhance industrial processes towards sustainability and efficiency.The versatility of EPS underscores its transformative impact on environmental and industrial practices.展开更多
文摘Geopolymers are an alternative to Portland cement, well known for their contribution to greenhouse gas emissions. Finding materials that can validly replace Portland cement is a challenge. It is in this logic that this work was undertaken with the objective of characterizing two local clay resources of Togo as raw materials for geopolymers. The physico-chemical properties of these clays were determined by characterization using X-ray diffraction (XRD), Fourier transform infrared (FTIR), thermogravimetric (TGA) and elemental analysis (ICP-OES). The results show that these clays contain kaolinite and therefore can be used in the formulation of geopolymers. The characterized clays underwent heat treatments transforming the crystalline phases into more reactive amorphous phases and then were activated by an alkaline solution in order to formulate the geopolymer materials. These elaborated materials were analyzed by Fourier transform infrared to identify the types of bonds formed. The results of these analyses show that these two local clays are well suited to be used in synthesizing geopolymers. Our future work will focus on the constraints of consolidation as well as the mechanical properties of these geopolymer materials.
文摘In the framework of various phosphates discharges valorization, we have realized physicochemical and mineralogical characterizations of these discharges. We have undertaken the physicochemical and mineralogical characterizations of this waste by Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Diffraction (XRD), thermal analysis and Atomic Emission Spectrometry Coupled to an Inductive Plasma Source. The results of these analyze show that phosphate sludge and screen rejects could be used in ceramics, in the manufacture of aggregates, in agriculture and other fields. On the other hand, rich magnetic waste could be used in heterogeneous photocatalysis in waste liquids treatment.
文摘In C ?te d’Ivoire, traditional ceramics are widely used in the form of pottery. The latter is used to store food, water and cereals. Analyzes (X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), inductive plasma optical emission spectrometry (ICP-OES), scanning electron microscopy (SEM) and analysis thermal gravimetric (ATG)) were carried out to determine the morphology, the chemical, physical and pedological constituents of these raw materials. It appears from this study that the clays used in the Mangoro pottery of Katiola contain silica SiO<sub>2</sub>, alumina Al<sub>2</sub>O<sub>3</sub> and iron oxide Fe<sub>2</sub>O<sub>3</sub> as well as kaolinite, muscovite, smectite and quartz.
文摘The objective of this study is to develop carbon, that of <i></span><i><span style="font-family:Verdana;">Acacia auriculeaformis</span></i><span style="font-family:Verdana;"></i></span><span style="font-family:Verdana;"> through its activation in order to eliminate lead in an aqueous medium. A series of activated carbon has been prepared by chemical activation with phosphoric acid, sodium hydroxide and sodium chloride. The determi</span><span style="font-family:Verdana;">nation of the physico-chemical properties of the prepared carbon guided the choice of phosphoric acid activated carbon as the best adsorbent for the</span><span style="font-family:Verdana;"> elimination of lead(II) in </span></span></span><span style="font-family:Verdana;"><span style="font-family:Verdana;"><span style="font-family:Verdana;">an </span></span></span><span><span><span style="font-family:""><span style="font-family:Verdana;">aqueous solution. Pb</span><sup><span style="font-family:Verdana;">2+</span></sup><span style="font-family:Verdana;"> adsorption tests in batch mode have shown that the adsorption capacity is influenced by various parameters such as mass, pH, concentration of Pb<sup>2+</sup> ions and contact time linked to the medium and the adsorbent. Adsorption isotherms, kinetic models and thermodynamics have been used to describe the adsorption process. The equilibrium data for activated charcoal correspond well to the model of Freundlich, </span><span style="font-family:Verdana;">Langmuir, Temkin and Kiselev. The kinetic adsorption data proved to be </span><span style="font-family:Verdana;">better described by the pseudo-second order model with </span><span style="font-family:Verdana;">external and intraparticle diffusion which are two decisive steps in the</span><span style="font-family:Verdana;"> adsorption process of Pb<sup>2+</sup> ions. Thermodynamics and adsorption isotherms predict a spontaneous exothermic surface reaction, of the chemisorption type, with ion </span><span><span style="font-family:Verdana;">retention in orderly monolayers on the heterogeneous surface of the adsorbent. Tests carried out with this adsorbent material have contributed to the elimination of the Pb</span><sup><span style="font-family:Verdana;">2+</span></sup><span style="font-family:Verdana;"> ions contained in an industrial effluent with a </span></span><span style="font-family:Verdana;">reduction rate reaching 42.52% against 85.90% in a synthetic solution.
基金the National Sciences and Engineering Research Council of Canada (NSERC Grant Number: I2IPJ 461378)
文摘Highly hydrophobic Di 2-ethyl hexyl phthalate（DEHP） is one of the most prevalent plasticizers in wastewaters. Since its half-life in biological treatment is around 25 days, it can be used as an efficiency indicator of wastewater treatment plant for the removal of hydrophobic emerging contaminants. In this study, the performance of submerged membrane bioreactor was monitored to understand the effect of DEHP on the growth of aerobic microorganisms. The data showed that the chemical oxygen demand（COD）and ammonia concentration were detected below 10 and 1.0 mg/L, respectively for operating conditions of hydraulic retention time（HRT） = 4 and 6 hr, sludge retention time（SRT） = 140 day and sludge concentration between 11.5 and 15.8 g volatile solid（VS）/L. The removal efficiency of DEHP under these conditions was higher and ranged between 91% and 98%. Results also showed that the removal efficiency of DEHP in biological treatment depended on the concentration of sludge, as adsorption is the main mechanism of its removal. For the submerged membrane bioreactor, the pore size is the pivotal factor for DEHP removal, since it determines the amount of soluble microbial products coming out of the process. Highly assimilated microorganisms increase the biodegradation rate, as 74% of inlet DEHP was biodegraded; however, the concentration of DEHP inside sludge was beyond the discharge limit. Understanding the fate of DEHP in membrane bioreactor,which is one of the most promising and futuristic treatment process could provide replacement for conventional processes to satisfy the future stricter regulations on emerging contaminants.
文摘The objective of this work is to prepare one of the best activated carbon (CA) based on wood (Acacia auriculeaformis). The chemical activation method was used for varying the chemical agent namely phosphoric acid H3PO4 (CAA), sodium hydroxide NaOH (CAB), and sodium chloride NaCl (CAS). The physico-chemical analysis of the three activated carbons indicated that, under the conditions of preparation, the activated carbons possess activation efficiencies lower than 50% (41.81% for CAA, 26.25% for CAB and 48.87% for CAS), low ash content (CAA: 5.00%, CAB: 14.90 and CAS: 6.60%) and iodine values ranging from 190.35 mg/g to 380.71 mg/g, suggesting that the good quality of the prepared activated carbon. The surface functional groups using Boehm test and the zero point charge (pHZPC) methods confirmed the acidic, basic and neutral character for CAA, CAB and CAS respectively (CAA: pHZPC = 4.8, CAB: pHZPC = 8.2, CAS: pHZPC = 6.8). The surface specific areas were determined through the liquid phase adsorption of acetic acid and methylene blue using the Langmuir method and BET analysis. Also, the porosity was determined. The BET surface areas of CAA, CAB and CAS were respectively 561.60 m2/g, 265.00 m2/g and 395.40 m2/g. The influence of chemical activation agent on pores formation was confirmed by scanning electron microscopic (SEM) analysis. CAA was selected as the best activated carbon because of its good surface area and good pore volume compared to those found in the literature. Therefore, its application as an adsorbent for effluents treatment could be explored. In addition, the best activating agent for coal from Acacia auriculeaformis was found to be phosphoric acid.
文摘In this work, low cost coconut biochar based activated carbon (CBAC) was used for adsorption of Butylparaben (BPB) from aqueous medium. The prepared CBAC was characterized using BET, Boehm analysis and the adsorption equilibrium, kinetics and thermodynamics studies of BPB adsorption were carried out. During batch adsorption runs, the effects of factors, such as contact time (0 - 300 min), CBAC dose (200 - 800 mg), pH (3 - 11) and solution temperatures (303 - 348 K) were investigated on BPB removal. Experimental results reveal that the BPB removal efficiency on CBAC is higher than 97% under acidic and neutral conditions. Equilibrium data were fitted by Langmuir, Freundlich and Temkin isotherm models with correlation coefficient more than 0.9. The pseudo-second order kinetic model was observed to fit well the adsorption data. Thermodynamic analysis shows positive values of standard Gibb’s free energy, suggesting the non-spontaneity of the process. The changes in enthalpy (0.2 J.mol-1) and entropy (19 J.mol-1) were found to be endothermic with an increase of randomness. The high adsorption efficiency of the synthesized coconut biochar materials with low cost indicates that it may be a promising adsorbent for removing organic compounds.
文摘Photocatalytic degradation of paraquat (PQ) aqueous solutions was studied in a fixed bed photoreactor under UV irradiation at 368 nm. This contained β-SiC alveolar foams coated with TiO2 P25 by dip-coating method. SEM analyses revealed that the surface of the film did not exhibit cracks in the presence of TTIP as a binder in the TiO2 P25 suspension. The following parameters were studied in continuous mode operation: the flow rate in the reactor, the initial concentration of the paraquat, the pH of the solution, the weight of photocatalytic material with the number of foams in the reactor and the weight of the catalyst deposited onto the support. The results showed that by working under optimal operating conditions at natural pH (pH = 6.7), low paraquat (Co = 10 ppm), and flow (26 mL/min), we recorded approximately (43.16 ± 1.00)% oxidation of paraquat and a decrease in total organic carbon (TOC) of (27.13 ± 1.00)% after about 70 minutes. The apparent rate constant is in the order of (0.0656 ± 0.0010) min-1. In addition, by increasing the amount of β-SiC foams coated with TiO2, we improve the degradation of paraquat in the same order. The study of aging of the material showed its stability over time. However, photocatalytic activity was limited after 20 minutes of UV irradiation due to the limitation of the diffusion of the paraquat molecules towards the surface of the photocatalyst. As an outcome, we obtained an efficient TiO2/β-SiC material for photocatalytic degradation of organic compounds in water.
文摘The development of biofuels is driven both by concern about the greenhouse effect and by interest in the opportunities for exploitation of biomass of agricultural origin. In order to improve the yield and quality of biodiesel through modeling and optimization, several studies are in progress. In this paper, biodiesel produced from rubber seed oil in the homogeneous transesterification is studied using a Plackett-Burman experimental design, a full factorial design, a central composite design and an Artificial Neural Network (ANN) coupled with a Genetic Algorithm (GA).Variables such as temperature, stirring speed, reaction time, type of alcohol, and type of catalyst are studied to obtain the best specific gravity and kinematic viscosity. Type of alcohol and type of catalyst have the greatest effect on the two responses, with ethanol (alcohol) and sulphuric acid (catalyst) producing the best results. The specific gravity and kinematic viscosity changes recorded during the transesterification process followed the first and second order polynomial models, respectively. The ANN coupled with GA was used to optimize the two responses simultaneously. Global optimal values of specific gravity (0.883) and kinematic viscosity (6.76 cSt) were recorded when a temperature of 90°C, a stirring speed of 305 rpm, and a treatment time of 141 min were imposed.
文摘The environmental problems caused by plastics of fossil origin are well known. To reduce harmful impact on the environment, bacterial-based plastics, such as polyhydroxyalkanoates (PHAs), are a promising solution. Microbial PHAs can be produced using abundant and inexpensive agricultural by-products as raw material. In this study, the potential use of Cupriavidus necator 11599 for the bioconversion of cassava starch into biodegradable PHAs was explored. Although Cupriavidus necator 11599 is a well-known PHA producer, it cannot grow directly on starch. Thus, acid hydrolysis was carried out on the starch extracted from cassava peels to obtain fermentable sugars. Optimal concentration of reducing sugars (RSs) was obtained by hydrolysis of cassava peel starch with sulfuric acid concentrations of 0.4 N and 0.6 N, at 95˚C and 4 h. The hydrolyzed starch was used for PHA production in Erlenmeyer flasks using reducing sugars (RSs) concentrations ranging from 10 g/L to 25 g/L. The best RS concentration 20 g/L and 25 g/L gave 85.13% ± 1.17% and 89.01% ± 2.49% of biomass PHA content and biomass concentrations of 8.18 g/L and 8.32 g/L, respectively in 48 hours. This research demonstrates that cassava peel starch as an inexpensive feedstock could be used for PHA production, paving the way for the use of other starchy materials to make bioplastics.
基金This research has been funded by the Natural Sciences and Engineering Research Council of Canada(Grant A4984).
文摘In the present study,municipal secondary sludge and purified glycerol(obtained after acid treatment of crude glycerol)were used together for lipid production using intermittent feeding strategy.Intermittent sludge feeding strategy(sludge SS 30 g/L)resulted in a higher biomass(54.99 g/L)and lipid concentration(25.35 g/L)at 96 h when compared to 35 g/L SS single sludge feeding or control strategy(45.67 g/L biomass&19.16 g/L lipid).Moreover,the intermittent sludge feeding strategy significantly reduced foaming and requirement of anti-foam during fermentation when compared to control strategy.The energy balance of biodiesel production from lipid obtained by intermittent sludge feeding strategy(30 g/L SS)was energeti-cally favorable.It was also revealed from yield coefficients and energy balance that sludge had an important contribution in microbial lipid and biodiesel production.
文摘Purified glycerol obtained after acid treatment of crude glycerol solution was used as the carbon source for lipid and citric acid production using Y.lipolytica SKY7.Although purified glycerol was high in phosphorus,it was important to inves-tigate the impact of fortification of trace elements in the medium on cell growth,lipid and citric acid(CA)production.When all the trace elements(including phosphates and sulfates)required for growth and lipid production were added to the purified glycerol medium,high biomass(51.67 g/L)and lipid concentration(19.47 g/L)were observed at 96 h of fed-batch fermentation with low CA concentration of 5.42 g/L.The purified glycerol medium without additional trace elements gave low biomass(27.67 g/L),lipid concentration(9.35 g/L)at 80 h of fed-batch fermentation,but gave high CA concentration(24.51 g/L).When purified glycerol was provided with only sulfates or all elements except KH_(2)PO_(4),low biomass(32.59 g/L and 38.52 g/L)and citric acid concentration(1 g/L and 2.42 g/L)were obtained at 96 h.
基金The authors thank the Natural Sciences and Engineering Research Council of Canada,Canada(NSERC-STPGP-479160 Strategic grant,Premier Tech Ltée,Canada Research Chair)for financial support.
文摘The study was conducted to investigate the effect of sludge retention on bacterial community composition of membrane bioreactor(MBR)treating synthetic hospital wastewater.The removal of four pharmaceuticals,namely carbamazepine,estradiol,venlafaxine,and ibuprofen in MBR,was studied at varying sludge retention time(SRT)duration of 100,45,and 15 days and hydraulic retention time(HRT)of 18 h.The removal of ibuprofen and estradiol was constant at varying SRT;however,a negligible removal of carbamazepine and low removal of venlafaxine was observed(<20%).The study suggested that the SRT of 45 days in MBR could provide maximum treatment efficiency via decreasing membrane clogging.The effect of sludge age and pharmaceutical presence on the bacterial community was investigated via high-throughput sequencing.The study reveals that the variation in SRT affects the dynamics of the bacterial community significantly.For instance,the dominant bacterium Caldimonas of SRT 100 was disappeared at lower SRTs.Moreover,the profile of the dominant genus of the SRTs varied greatly from each other.
基金National Sciences and Engineering Research Council of Canada(NSERC),No.498017-2017,Allali Patrick Drogui.
文摘Extracellular polymeric substances(EPSs)play a crucial role in various applications,especially in wastewater treatment.This review explores the importance of EPS in modern treatment methods,emphasizing its organic polymeric nature and properties that aid in effective pollutant removal and resource conservation.The study focuses on biological strategies utilizing microbial and bacterial communities,as well as electrolyte precipitate systems containing various components such as uronic acids,proteins,and carbohydrates that are essential for treatment processes.This review also describes the complex mechanisms regulating EPS biosynthesis,highlighting the impact of factors such as temperature,light intensity,and carbon to nitrogen ratio on EPS production.These findings emphasizes the influence of carbon supply and nitrogen sources on EPS formation,shedding light on the relationship between environmental conditions and EPS synthesis.In addition,this study discusses the significance of EPS extraction techniques for maintaining material integrity.Furthermore,the review explores the broad applications of EPS beyond wastewater treatment,including soil aggregation,pharmaceuticals,the food industry,and sustainable energy generation through EPS-driven microbial fuel cells.Understanding the diverse functions of EPS has the potential to improve environmental practices,mitigate climate change effects,and enhance industrial processes towards sustainability and efficiency.The versatility of EPS underscores its transformative impact on environmental and industrial practices.
