Between the two major arsenic-containing salts in natural water, arsenite(As(Ⅲ)) is far more harmful to human and the environment than arsenate(As(V)) due to its high toxicity and transportability. Therefore, preoxid...Between the two major arsenic-containing salts in natural water, arsenite(As(Ⅲ)) is far more harmful to human and the environment than arsenate(As(V)) due to its high toxicity and transportability. Therefore, preoxidation of As(Ⅲ) to As(V) is considered to be an effective means to reduce the toxicity of arsenic and to promote the removal efficiency of arsenic. Due to their high catalytic activity and arsenic affinity, iron-based functional materials can quickly oxidize As(Ⅲ) to As(V) in heterogeneous Fenton-like systems, and then remove As(V) from water through adsorption and surface coprecipitation. In this review, the effects of different iron-based functional materials such as zero-valent iron and iron(hydroxy) oxides on arsenic removal are compared, and the catalytic oxidation mechanism of As(Ⅲ) in heterogeneous Fenton process is further clarified. Finally, the main challenges and opportunities faced by iron-based As(Ⅲ) oxidation functional materials are prospected.展开更多
A semicircular section tubular photoreactor has been constructed, characterized and applied to the treatment of groundwater contaminated with As（V） by means of the SORAS （solar oxidation and removal of arsenic） te...A semicircular section tubular photoreactor has been constructed, characterized and applied to the treatment of groundwater contaminated with As（V） by means of the SORAS （solar oxidation and removal of arsenic） technique, using ferrous and citrate salts. The solar concentrator was built with recyclable waste materials： glass tubes from fluorescent lamps and 6-inch diameter PVC pipes cut in half and covered by aluminum foil. The reactor concentrates solar radiation up to 2.8 times its natural intensity. Batch irradiation experiments followed by controlled agitation （shear rate = 30-33 s^-1; 20 min agitation period） showed that the photoreactor accelerates the formation of settleable floccules （Dp 〉 0.5mm）, compared with a fluorescent lamp glass tube alone and a 2 L PET （polyethylene terephthalate） bottle. Irradiation times necessary for floccule formation in the photoreactor, the fluorescent lamp tube and the PET bottle were 15 min, 25 min and 60 min, respectively. Continuous flow experiments using a photoreactor with a photo-collection area of 0.9 m^2 and a hydraulic retention time （equal to the irradiation time） of 15 rain showed that immediate formation of floccules of good settleability occurs when the solution is subjected to moderate agitation （33 s^-1）. An efficiency of 98.36% for As（V） removal was obtained with a final concentration of 16.5 ktg/L in decanted waters. In accordance to these results, the photoreactor is able to treat approximately 130 L/m^2 within a 5-h period with UVA irradiation intensities of 50-70 W/mE.展开更多
Immobilization of hydrous ferric oxide(HFO) particles inside solid hosts of porous structure is an important approach to improve their applicability in advanced water treatment such as arsenic and heavy metal removal....Immobilization of hydrous ferric oxide(HFO) particles inside solid hosts of porous structure is an important approach to improve their applicability in advanced water treatment such as arsenic and heavy metal removal. Here, we fabricated three polystyrene(PS)-based nano-HFOs and explored the effect of host pore structure on the surface chemistry of the immobilized HFOs. Potentiometric titration of the hybrids and surface complexation modeling of their adsorption towards arsenite and arsenate were performed to evaluate the surface chemistry variation of the loaded HFOs. Polymer hosts of higher surface area and narrower pore size would result in smaller particle size of HFOs and lower the value of the point of zero charge. Also, the site density(normalized by Fe mass) and the deprotonation constants of the loaded HFOs increased with the decreasing host pore size. Arsenite adsorption did not change the surface charge of the loaded HFOs, whereas arsenate adsorption accompanied more of the negative surface charges. Adsorption affinity of both arsenic species with three HFO hybrids were compared in terms of the intrinsic surface complexation constants optimized based on the adsorption edges. HFO loaded in polystyrene host of smaller pore size exhibits stronger affinity with arsenic species.展开更多
基金financially supported by the National Science Fund for Excellent Young Scholars of China (No. 52022111)the Distinguished Young Scholars of China (No. 51825403)the National Natural Science Foundation of China (Nos. 51634010, 51974379)。
文摘Between the two major arsenic-containing salts in natural water, arsenite(As(Ⅲ)) is far more harmful to human and the environment than arsenate(As(V)) due to its high toxicity and transportability. Therefore, preoxidation of As(Ⅲ) to As(V) is considered to be an effective means to reduce the toxicity of arsenic and to promote the removal efficiency of arsenic. Due to their high catalytic activity and arsenic affinity, iron-based functional materials can quickly oxidize As(Ⅲ) to As(V) in heterogeneous Fenton-like systems, and then remove As(V) from water through adsorption and surface coprecipitation. In this review, the effects of different iron-based functional materials such as zero-valent iron and iron(hydroxy) oxides on arsenic removal are compared, and the catalytic oxidation mechanism of As(Ⅲ) in heterogeneous Fenton process is further clarified. Finally, the main challenges and opportunities faced by iron-based As(Ⅲ) oxidation functional materials are prospected.
文摘A semicircular section tubular photoreactor has been constructed, characterized and applied to the treatment of groundwater contaminated with As（V） by means of the SORAS （solar oxidation and removal of arsenic） technique, using ferrous and citrate salts. The solar concentrator was built with recyclable waste materials： glass tubes from fluorescent lamps and 6-inch diameter PVC pipes cut in half and covered by aluminum foil. The reactor concentrates solar radiation up to 2.8 times its natural intensity. Batch irradiation experiments followed by controlled agitation （shear rate = 30-33 s^-1; 20 min agitation period） showed that the photoreactor accelerates the formation of settleable floccules （Dp 〉 0.5mm）, compared with a fluorescent lamp glass tube alone and a 2 L PET （polyethylene terephthalate） bottle. Irradiation times necessary for floccule formation in the photoreactor, the fluorescent lamp tube and the PET bottle were 15 min, 25 min and 60 min, respectively. Continuous flow experiments using a photoreactor with a photo-collection area of 0.9 m^2 and a hydraulic retention time （equal to the irradiation time） of 15 rain showed that immediate formation of floccules of good settleability occurs when the solution is subjected to moderate agitation （33 s^-1）. An efficiency of 98.36% for As（V） removal was obtained with a final concentration of 16.5 ktg/L in decanted waters. In accordance to these results, the photoreactor is able to treat approximately 130 L/m^2 within a 5-h period with UVA irradiation intensities of 50-70 W/mE.
基金supported by the National Natural Science Foundation of China(21177059/51378079)the Jiangsu Natural Science Foundation(BK2012017)
文摘Immobilization of hydrous ferric oxide(HFO) particles inside solid hosts of porous structure is an important approach to improve their applicability in advanced water treatment such as arsenic and heavy metal removal. Here, we fabricated three polystyrene(PS)-based nano-HFOs and explored the effect of host pore structure on the surface chemistry of the immobilized HFOs. Potentiometric titration of the hybrids and surface complexation modeling of their adsorption towards arsenite and arsenate were performed to evaluate the surface chemistry variation of the loaded HFOs. Polymer hosts of higher surface area and narrower pore size would result in smaller particle size of HFOs and lower the value of the point of zero charge. Also, the site density(normalized by Fe mass) and the deprotonation constants of the loaded HFOs increased with the decreasing host pore size. Arsenite adsorption did not change the surface charge of the loaded HFOs, whereas arsenate adsorption accompanied more of the negative surface charges. Adsorption affinity of both arsenic species with three HFO hybrids were compared in terms of the intrinsic surface complexation constants optimized based on the adsorption edges. HFO loaded in polystyrene host of smaller pore size exhibits stronger affinity with arsenic species.
