Humic acid(HA)can adsorb onto mineral surfaces,modifying the physicochemical properties of the mineral.Therefore,understanding the sorption behavior of HA onto mineral surfaces is of particular interest,since the fate...Humic acid(HA)can adsorb onto mineral surfaces,modifying the physicochemical properties of the mineral.Therefore,understanding the sorption behavior of HA onto mineral surfaces is of particular interest,since the fate and transport of many organic and inorganic contaminants are highly correlated to HA adsorbed onto clay surfaces.Due to the extreme heterogeneity of HA,the extracted IHSS Leonardite humic acid(LHA)used in this work was fractionated using an ultrafiltration technique(UF)into different molecular size fractions(Fr1,>0.2μm;Fr2,0.2 pm-300,000 daltons;Fr3,300,000-50,000 daltons;Fr4,50,000-10,000 daltons;Fr5,10,000-1000 daltons).Equilibrium and the kinetics of LHA and fraction adsorption onto kaolinite and montmorillonite were investigated.The results demonstrated that the maximum adsorption capacity of LHA,Frl,Fr2,Fr3,Fr4,and Fr5 was 5.99,13.69,10.29,7.02,5.9&and 5.09 on kaolinite while it was 8.29,22.62,13.17,8.91,8.62,and 5.69 on montmorillonite,respectively.The adsorption equilibrium data showed that the adsorption behavior of LHA and its fractions could be described more practically by the Langmuir model than the Freundlich model.The rate of humic acid fraction adsorption onto clays increased with decreasing molecular size fraction and increasing carboxylic group content.Pseudo-first-and second-order models were used to assess the kinetic data and the rate constants.The results explained that LHA and its fractions adsorption on clay minerals conformed more to pseudosecondo rder.展开更多
The capacity of humic acid extracted from organic waste （HAw） to reduce Cr（Ⅵ） was tested at pH 2.5,4 and 6 and compared with coal-derived humic acid （HAc）.HAw was more effective than HAc in reducing Cr（Ⅵ）.Th...The capacity of humic acid extracted from organic waste （HAw） to reduce Cr（Ⅵ） was tested at pH 2.5,4 and 6 and compared with coal-derived humic acid （HAc）.HAw was more effective than HAc in reducing Cr（Ⅵ）.The kinetics of Cr（Ⅵ） reductions depended strongly on pH.The calculation of the apparent rate coefficients indicated that HAw was more efficient at reducing Cr（Ⅵ） than HAc,but was also more efficient than HAs from soil and peat.The reduction capability of HAs depends on the type of functional groups （i.e.,thiols and phenols） present,rather than the free radicals.HAw was more efficient at reducing Cr（Ⅵ） than HAc because more reactive phenols were present,i.e.,methoxy-and methyl-phenols.展开更多
The phosphorus（P） fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid（HA） complexes were analyzed using the ultrafiltration method in this...The phosphorus（P） fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid（HA） complexes were analyzed using the ultrafiltration method in this study.With an initial P concentration of 20 mg/L（I =0.01 mol/L and pH = 7）,it was shown that the colloid（1 kDa-0.45 μm） component of P accounted for 10.6%,11.6%,6.5%,and 4.0%of remaining total P concentration in the supernatant after P adsorption onto ferrihydrite（FH）,goethite（GE）,ferrihydrite-humic acid complex（FH-HA）,goethite-humic acid complex（GE-HA）,respectively.The 〈1 kDa component of P was still the predominant fraction in the supernatant,and underestimated colloidal P accounted for 2.2%,55.1%,45.5%,and 38.7%of P adsorption onto the solid surface of FH,FH-HA,GE and GE-HA,respectively.Thus,the colloid P could not be neglected.Notably,it could be interpreted that Fe3＋ hydrolysis from the adsorbents followed by the formation of colloidal hydrous ferric oxide aggregates was the main mechanism for the formation of the colloid P in the supernatant.And colloidal adsorbent particles co-existing in the supernatant were another important reason for it.Additionally,dissolve organic matter dissolved from iron oxide-HA complexes could occupy large adsorption sites of colloidal iron causing less colloid P in the supernatant.Ultimately,we believe that the findings can provide a new way to deeply interpret the geochemical cycling of P,even when considering other contaminants such as organic pollutants,heavy metal ions,and arsenate at the sediment/soil-water interface in the real environment.展开更多
以城市污水厂二级出水为研究对象,利用大孔吸附树脂将污水中溶解性有机物(Dissolved organic matter,DOM)分离成疏水酸性、中性、碱性物质和亲水性物质等4个组分,同时分析了各组分的有机物特性.结果表明,二级出水溶解性有机物中疏水酸...以城市污水厂二级出水为研究对象,利用大孔吸附树脂将污水中溶解性有机物(Dissolved organic matter,DOM)分离成疏水酸性、中性、碱性物质和亲水性物质等4个组分,同时分析了各组分的有机物特性.结果表明,二级出水溶解性有机物中疏水酸性物质是二级出水溶解性有机物的主要组成部分.4种组分中均含有腐殖质类物质,疏水酸性物质(Hydrophobic acids,HOA)和疏水中性物质(Hydrophobic neutrals,HON)中腐殖酸类峰的荧光强度较大,亲水性物质(Hydrophilic fraction,HI)中的蛋白峰荧光强度较大.腐殖质类物质分子量分布较为单一,主要分布在0.9 k Da左右,而疏水性组分蛋白类物质分子量分布较为广泛,在200 k Da左右及小于9 k Da时均有一定分布,亲水性组分蛋白类物质主要由分子量小于9 k Da的物质组成.X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)分析结果表明,HOA、HON中含有较多的芳香族化合物,而疏水碱性物质(Hydrophobic bases,HOB)、HI中则含有较多的羰基和羧基类官能团.展开更多
基金funded by a Fulbright Visiting Scholar fellowship to Mohamed El-sayed and performed at South Dakota State University
文摘Humic acid(HA)can adsorb onto mineral surfaces,modifying the physicochemical properties of the mineral.Therefore,understanding the sorption behavior of HA onto mineral surfaces is of particular interest,since the fate and transport of many organic and inorganic contaminants are highly correlated to HA adsorbed onto clay surfaces.Due to the extreme heterogeneity of HA,the extracted IHSS Leonardite humic acid(LHA)used in this work was fractionated using an ultrafiltration technique(UF)into different molecular size fractions(Fr1,>0.2μm;Fr2,0.2 pm-300,000 daltons;Fr3,300,000-50,000 daltons;Fr4,50,000-10,000 daltons;Fr5,10,000-1000 daltons).Equilibrium and the kinetics of LHA and fraction adsorption onto kaolinite and montmorillonite were investigated.The results demonstrated that the maximum adsorption capacity of LHA,Frl,Fr2,Fr3,Fr4,and Fr5 was 5.99,13.69,10.29,7.02,5.9&and 5.09 on kaolinite while it was 8.29,22.62,13.17,8.91,8.62,and 5.69 on montmorillonite,respectively.The adsorption equilibrium data showed that the adsorption behavior of LHA and its fractions could be described more practically by the Langmuir model than the Freundlich model.The rate of humic acid fraction adsorption onto clays increased with decreasing molecular size fraction and increasing carboxylic group content.Pseudo-first-and second-order models were used to assess the kinetic data and the rate constants.The results explained that LHA and its fractions adsorption on clay minerals conformed more to pseudosecondo rder.
文摘The capacity of humic acid extracted from organic waste （HAw） to reduce Cr（Ⅵ） was tested at pH 2.5,4 and 6 and compared with coal-derived humic acid （HAc）.HAw was more effective than HAc in reducing Cr（Ⅵ）.The kinetics of Cr（Ⅵ） reductions depended strongly on pH.The calculation of the apparent rate coefficients indicated that HAw was more efficient at reducing Cr（Ⅵ） than HAc,but was also more efficient than HAs from soil and peat.The reduction capability of HAs depends on the type of functional groups （i.e.,thiols and phenols） present,rather than the free radicals.HAw was more efficient at reducing Cr（Ⅵ） than HAc because more reactive phenols were present,i.e.,methoxy-and methyl-phenols.
基金supported by the National Natural Science Foundation of China(nos.41171198,41403079)the Chongqing Research Program of Basic Research and Frontier Technology(no.cstc2015jcyj A20021)the Fundamental Research Funds for the Central Universities of Ministry of Education of China(no.XDJK2015B035)
文摘The phosphorus（P） fraction distribution and formation mechanism in the supernatant after P adsorption onto iron oxides and iron oxide-humic acid（HA） complexes were analyzed using the ultrafiltration method in this study.With an initial P concentration of 20 mg/L（I =0.01 mol/L and pH = 7）,it was shown that the colloid（1 kDa-0.45 μm） component of P accounted for 10.6%,11.6%,6.5%,and 4.0%of remaining total P concentration in the supernatant after P adsorption onto ferrihydrite（FH）,goethite（GE）,ferrihydrite-humic acid complex（FH-HA）,goethite-humic acid complex（GE-HA）,respectively.The 〈1 kDa component of P was still the predominant fraction in the supernatant,and underestimated colloidal P accounted for 2.2%,55.1%,45.5%,and 38.7%of P adsorption onto the solid surface of FH,FH-HA,GE and GE-HA,respectively.Thus,the colloid P could not be neglected.Notably,it could be interpreted that Fe3＋ hydrolysis from the adsorbents followed by the formation of colloidal hydrous ferric oxide aggregates was the main mechanism for the formation of the colloid P in the supernatant.And colloidal adsorbent particles co-existing in the supernatant were another important reason for it.Additionally,dissolve organic matter dissolved from iron oxide-HA complexes could occupy large adsorption sites of colloidal iron causing less colloid P in the supernatant.Ultimately,we believe that the findings can provide a new way to deeply interpret the geochemical cycling of P,even when considering other contaminants such as organic pollutants,heavy metal ions,and arsenate at the sediment/soil-water interface in the real environment.
基金Project(42030711)supported by the Key Project of National Natural Science Foundation of ChinaProject(42177391)supported by the National Natural Science Foundation of China。
文摘以城市污水厂二级出水为研究对象,利用大孔吸附树脂将污水中溶解性有机物(Dissolved organic matter,DOM)分离成疏水酸性、中性、碱性物质和亲水性物质等4个组分,同时分析了各组分的有机物特性.结果表明,二级出水溶解性有机物中疏水酸性物质是二级出水溶解性有机物的主要组成部分.4种组分中均含有腐殖质类物质,疏水酸性物质(Hydrophobic acids,HOA)和疏水中性物质(Hydrophobic neutrals,HON)中腐殖酸类峰的荧光强度较大,亲水性物质(Hydrophilic fraction,HI)中的蛋白峰荧光强度较大.腐殖质类物质分子量分布较为单一,主要分布在0.9 k Da左右,而疏水性组分蛋白类物质分子量分布较为广泛,在200 k Da左右及小于9 k Da时均有一定分布,亲水性组分蛋白类物质主要由分子量小于9 k Da的物质组成.X射线光电子能谱(X-ray photoelectron spectroscopy,XPS)分析结果表明,HOA、HON中含有较多的芳香族化合物,而疏水碱性物质(Hydrophobic bases,HOB)、HI中则含有较多的羰基和羧基类官能团.
