At present,standard discharge has been adopted in the treatment of shale gas drilling wastewater and the electro-flocculation pretreatment has a good application prospect due to its high efficiency,cleanness,low dosag...At present,standard discharge has been adopted in the treatment of shale gas drilling wastewater and the electro-flocculation pretreatment has a good application prospect due to its high efficiency,cleanness,low dosage,etc.To improve its adaptability to drilling wastewater treatment,we conducted experiments to investigate the effects of current densities and reaction time on hardness,turbidity and organic matter removal,and the mechanism of electro-flocculation was further explored and a comparative analysis was made with chemical coagulation and ultrafiltration.The following findings were achieved.(1)The drilling wastewater is rich in dissolved salts,among which the hardness ions are mainly Ca^(2+),and the Ca^(2+) concentration varies little at the reaction time of 10 min,but decreases significantly with the increase of reaction time.(2)During the electro-flocculation process,the harness ions are usually removed with suspended matters,and their removal trend is different.Lower current densities and longer reaction time will be good for higher hardness removal rates,while higher current densities can help decrease the turbidity quickly before the reaction time of 10 min(3)The pH value of the wastewater is negatively correlated with the concentration of Ca^(2+) and iron ions.The TOC decreases with the increase of reaction time,and the larger the current density,the greater the decrease of TOC.A linear correlation is found between △TOC and △Cl^(-) and △Turbidity.Compared with chemical coagulation and ultrafiltration,electro-flocculation presents significant removal effects of hardness and turbidity.When the current density is 8 mA/cm^(2)and the reaction time is 20 min,the removal rates of Ca^(2+),turbidity and TOC are 53.4%,98.3%,and 62.7%,respectively.Especially for those macromolecular substances with conjugated double bonds,electro-flocculation has an obvious effect and has other advantages like no chemical dosing,no membrane pollution and short reaction time,and so on.展开更多
In Zimapan Valley, Mexico, up to 1.1 mg·L-1 of arsenic concentrations have been detected in deep wells that are used as drinking water supply for almost 39,000 people, which could have been exposed to level...In Zimapan Valley, Mexico, up to 1.1 mg·L-1 of arsenic concentrations have been detected in deep wells that are used as drinking water supply for almost 39,000 people, which could have been exposed to levels higher than 10 μg·L-1 of arsenic, the maximum level recommended by the World Health Organization. Chronic consumption of water contaminated with arsenic can cause several diseases, including cancer. For it, the implementation of practical and economical methods to remove arsenic from drinking water is crucial to protect the population health. In this work, an electrochemical method to remove arsenic from drinking water is described. The process, monitored by Tyndall effect, utilizes Cu2+ and Zn2+ ions from a brass electrode in an electrochemical cell with water as electrolyte. Results show that the EC process reduces the concentration of the arsenic diluted in Zimapan water to a level below the limit of detection of the atomic absorption spectrophotometer employed. Arsenic was removed through the formation of Cu and Zn arsenic compounds. Cu2+ and Zn2+ ions form a hydroxide and eventually polycrystalline precipitation of kottigite and cornubite complexes (identified by energy-dispersive X-ray spectroscopy and X-ray diffraction), which are then filtered to eliminate the precipitated arsenic compounds.展开更多
基金supported by a sub-project under The National Major Science and Technology Project,China“Waste Treatment and Utilization Technology”(No.:2016ZX05040-003)a sub-project under The CNPC Major Science and Technology Project,China“Research and Demonstration Application of Key Technology for Waste Treatment and Utilization in Shale Gas Development”(No.:2016E-1202).
文摘At present,standard discharge has been adopted in the treatment of shale gas drilling wastewater and the electro-flocculation pretreatment has a good application prospect due to its high efficiency,cleanness,low dosage,etc.To improve its adaptability to drilling wastewater treatment,we conducted experiments to investigate the effects of current densities and reaction time on hardness,turbidity and organic matter removal,and the mechanism of electro-flocculation was further explored and a comparative analysis was made with chemical coagulation and ultrafiltration.The following findings were achieved.(1)The drilling wastewater is rich in dissolved salts,among which the hardness ions are mainly Ca^(2+),and the Ca^(2+) concentration varies little at the reaction time of 10 min,but decreases significantly with the increase of reaction time.(2)During the electro-flocculation process,the harness ions are usually removed with suspended matters,and their removal trend is different.Lower current densities and longer reaction time will be good for higher hardness removal rates,while higher current densities can help decrease the turbidity quickly before the reaction time of 10 min(3)The pH value of the wastewater is negatively correlated with the concentration of Ca^(2+) and iron ions.The TOC decreases with the increase of reaction time,and the larger the current density,the greater the decrease of TOC.A linear correlation is found between △TOC and △Cl^(-) and △Turbidity.Compared with chemical coagulation and ultrafiltration,electro-flocculation presents significant removal effects of hardness and turbidity.When the current density is 8 mA/cm^(2)and the reaction time is 20 min,the removal rates of Ca^(2+),turbidity and TOC are 53.4%,98.3%,and 62.7%,respectively.Especially for those macromolecular substances with conjugated double bonds,electro-flocculation has an obvious effect and has other advantages like no chemical dosing,no membrane pollution and short reaction time,and so on.
文摘In Zimapan Valley, Mexico, up to 1.1 mg·L-1 of arsenic concentrations have been detected in deep wells that are used as drinking water supply for almost 39,000 people, which could have been exposed to levels higher than 10 μg·L-1 of arsenic, the maximum level recommended by the World Health Organization. Chronic consumption of water contaminated with arsenic can cause several diseases, including cancer. For it, the implementation of practical and economical methods to remove arsenic from drinking water is crucial to protect the population health. In this work, an electrochemical method to remove arsenic from drinking water is described. The process, monitored by Tyndall effect, utilizes Cu2+ and Zn2+ ions from a brass electrode in an electrochemical cell with water as electrolyte. Results show that the EC process reduces the concentration of the arsenic diluted in Zimapan water to a level below the limit of detection of the atomic absorption spectrophotometer employed. Arsenic was removed through the formation of Cu and Zn arsenic compounds. Cu2+ and Zn2+ ions form a hydroxide and eventually polycrystalline precipitation of kottigite and cornubite complexes (identified by energy-dispersive X-ray spectroscopy and X-ray diffraction), which are then filtered to eliminate the precipitated arsenic compounds.
