Red mud is the waste of alumina industry and has high TiO2 and Fe2O3 content which are active components for the adsorption of anion pollutants. In this study, the uptake of phosphate by red mud activated by heat trea...Red mud is the waste of alumina industry and has high TiO2 and Fe2O3 content which are active components for the adsorption of anion pollutants. In this study, the uptake of phosphate by red mud activated by heat treatment and acid-heat treatment was investigated. The factors influencing the adsorption were also investigated. The result showed that the red mud sample treated using acid-heat method at 80℃ with 0.25 mol/L HCl for 2 h achieved the highest phosphate removal. For the heat-activated red mud, the sample heated at 700℃ for 2 h preformed better than the other heat treatment. Phosphate removal by the activated red mud was significantly pH dependent, and pH 7 was the optimal pH for phosphate removal. The adsorption fits Langmuir isotherm model well and the maximum adsorption capacities of the acid-heat activated red mud and the heat activated samples were 202.9 mgP/g and 155.2 mgP/g, respectively.展开更多
For the removal of phosphate（PO43-） from water, an adsorbent was prepared via carbonization of sewage sludge from a wastewater treatment plant： carbonized sludge adsorbent（CSA）. The mechanism of phosphate removal...For the removal of phosphate（PO43-） from water, an adsorbent was prepared via carbonization of sewage sludge from a wastewater treatment plant： carbonized sludge adsorbent（CSA）. The mechanism of phosphate removal was determined after studying the structure and chemical properties of the CSA and its influence on phosphate removal. The results demonstrate that phosphate adsorption by the CSA can be fitted with the pseudo second-order kinetics and Langmuir isotherm models, indicating that the adsorption is single molecular layer adsorption dominated by chemical reaction. The active sites binding phosphate on the surface are composed of mineral particles containing Si/Ca/Al/Fe. The mineral containing Ca, calcite, is the main factor responsible for phosphate removal. The phosphate removal mechanism is a complex process including crystallization via the interaction between Ca2＋ and PO43-; formation of precipitates of Ca2＋, Al3＋, and PO43-; and adsorption of PO43-on some recalcitrant oxides composed of Si/Al/Fe.展开更多
Alkaline residue （AR） was found to be an efficient adsorbent for phosphate removal from wastewater. The kinetic and equilibrium of phosphate removal were investigated to evaluate the performance of modified alkaline...Alkaline residue （AR） was found to be an efficient adsorbent for phosphate removal from wastewater. The kinetic and equilibrium of phosphate removal were investigated to evaluate the performance of modified alkaline residue. After treatment by NaOH （AR-NaOH）, removal performance was significantly improved, while removal performance was almost completely lost after treatment by HCI （AR-HC1）. The kinetics of the removal process by all adsorbents was well characterized by the pseudo second-order model. The Langmuir model exhibited the best correlation for AR-HC1, while AR was effectively described by Freundlich model. Both models were well fitted to AR-NaOH. The maximum adsorption capacities calculated from Langmuir equation were in following manner： AR-NaOH 〉 AR 〉 AR-HC1. Phosphate removal by alkaline residue was pH dependent process. Mechanisms for phosphate removal mainly involved adsorption and precipitation, varied with equilibrium pH of solution. For AR-HCI, the acid equilibrium pH （〈 6.0） was unfavorable for the formation of Ca-P precipitate, with adsorption as the key mechanism for phosphate removal. In contrast, for AR and AR- NaOH, precipitation was the dominant mechanism for phosphate removal, due to the incrase on pH （〉 8.0） after phosphate removal. The results of both XRD and SEM analysis confirmed CaHPOa.2H20 formation after phosphate removal by AR and AR-NaOH.展开更多
基金Project supported by the National Natural Science Foundation of China (No.40673003).
文摘Red mud is the waste of alumina industry and has high TiO2 and Fe2O3 content which are active components for the adsorption of anion pollutants. In this study, the uptake of phosphate by red mud activated by heat treatment and acid-heat treatment was investigated. The factors influencing the adsorption were also investigated. The result showed that the red mud sample treated using acid-heat method at 80℃ with 0.25 mol/L HCl for 2 h achieved the highest phosphate removal. For the heat-activated red mud, the sample heated at 700℃ for 2 h preformed better than the other heat treatment. Phosphate removal by the activated red mud was significantly pH dependent, and pH 7 was the optimal pH for phosphate removal. The adsorption fits Langmuir isotherm model well and the maximum adsorption capacities of the acid-heat activated red mud and the heat activated samples were 202.9 mgP/g and 155.2 mgP/g, respectively.
基金financially supported by the National Key R&D Program of China(No.2016YFC0400804)
文摘For the removal of phosphate（PO43-） from water, an adsorbent was prepared via carbonization of sewage sludge from a wastewater treatment plant： carbonized sludge adsorbent（CSA）. The mechanism of phosphate removal was determined after studying the structure and chemical properties of the CSA and its influence on phosphate removal. The results demonstrate that phosphate adsorption by the CSA can be fitted with the pseudo second-order kinetics and Langmuir isotherm models, indicating that the adsorption is single molecular layer adsorption dominated by chemical reaction. The active sites binding phosphate on the surface are composed of mineral particles containing Si/Ca/Al/Fe. The mineral containing Ca, calcite, is the main factor responsible for phosphate removal. The phosphate removal mechanism is a complex process including crystallization via the interaction between Ca2＋ and PO43-; formation of precipitates of Ca2＋, Al3＋, and PO43-; and adsorption of PO43-on some recalcitrant oxides composed of Si/Al/Fe.
基金supported by the Technological Support Plan Foundation of Jiangsu Province of China(No.BE2011834)
文摘Alkaline residue （AR） was found to be an efficient adsorbent for phosphate removal from wastewater. The kinetic and equilibrium of phosphate removal were investigated to evaluate the performance of modified alkaline residue. After treatment by NaOH （AR-NaOH）, removal performance was significantly improved, while removal performance was almost completely lost after treatment by HCI （AR-HC1）. The kinetics of the removal process by all adsorbents was well characterized by the pseudo second-order model. The Langmuir model exhibited the best correlation for AR-HC1, while AR was effectively described by Freundlich model. Both models were well fitted to AR-NaOH. The maximum adsorption capacities calculated from Langmuir equation were in following manner： AR-NaOH 〉 AR 〉 AR-HC1. Phosphate removal by alkaline residue was pH dependent process. Mechanisms for phosphate removal mainly involved adsorption and precipitation, varied with equilibrium pH of solution. For AR-HCI, the acid equilibrium pH （〈 6.0） was unfavorable for the formation of Ca-P precipitate, with adsorption as the key mechanism for phosphate removal. In contrast, for AR and AR- NaOH, precipitation was the dominant mechanism for phosphate removal, due to the incrase on pH （〉 8.0） after phosphate removal. The results of both XRD and SEM analysis confirmed CaHPOa.2H20 formation after phosphate removal by AR and AR-NaOH.
