不同材料对高As污泥中As的固定效果

Immobilization effect of different materials on high As-bearing sludge

针对制酸行业产生的高砷(As)污泥浸出毒性过高且难处理的问题,选择典型无机硫化物、含钙材料、含铁或铝材料(Fe^0、铁盐、Fe^2O^3/Al^2O^3)对高As污泥进行固定化,采用醋酸(TCLP)、H2SO4-HNO3和H2O3种浸提法评估了各材料对As的固定效果;考察了固定化对污泥中As结合态和价态分布的影响,筛选最佳固定化材料,进行联合水泥固化。结果表明,FeCl^3固化As的效果最好,3种浸提法评估的固砷率分别为86.01%、42.02%、58.87%。FeCl^3和Fe^0处理能够促进污泥As向固定态转化,非专性和专性吸附态占比分别降低了80.60%和38.13%。FeCl^3促进非专性和专性吸附态向结晶铁锰或铁铝水化氧化物结合态和残渣态转化。CaO、Fe0、FeSO^4·7H^2O、Fe(NO^3)^3·9H^2O、FeCl^3和Fe^2O^12S^3处理对As(Ⅲ)具有一定的氧化作用。FeCl^3处理后,As(Ⅲ)占比由77.14%降为19.72%。Fe(OH)^3、Fe^2O^3和Al^2O^3处理对As(Ⅲ)的氧化性不明显,Na^2S·9H^2O处理使As(Ⅲ)占比升至85.84%。随FeCl^3、水泥和两者配伍材料投加量的增加,在3种方法中,污泥中As的浸出量均明显降低,单一FeCl^3和配伍固砷效果均优于水泥;水泥配伍比≥100%时的固砷效果优于单一FeCl^3;250%FeCl^3+125%水泥可使3种方法中浸出砷浓度降至最低,分别为113.81、399.28、347.27 mg·L^-1,固砷率均高于97%。本研究结果可为高As污泥的固定化提供参考。供参考。

The high arsenic(As)-bearing sludge produced from acid industry has too high leaching toxicity to dispose.In this study,three kinds of typical materials:inorganic sulfide,calcium-based material and several iron-aluminum-based materials(Fe^0,ferric salt,Fe^2O^3/Al^2O^3),were used to immobilize the high As-bearing sludge.Their As immobilization effects were assessed by three leaching methods of TCLP(toxicity characteristic leaching procedure),H^2SO^4-HNO^3 and H^2O.The effect of immobilization on the valence and binding form distribution of arsenic in sludge was investigated.Then the optimal material for As immobilization was determined,which was used to conduct the subsequent joint solidification with cement.The screening result of materials showed that FeCl^3 had the best As immobilization effect,and its As immobilization efficiencies assessed by above three leaching methods were 86.01%,42.02%,58.87%,respectively.The FeCl^3 or Fe^0 treatment could promote the As transformation to stable speciation,and the proportions of non-specific and specific bound As fractions decreased by 80.60%and 38.13%,respectively.In which FeCl^3 treatment promoted the transformation from non-specific and specific bound As fractions to crystalline hydrous Fe(Mn,Al)oxide fraction and residual fraction.CaO,Fe0,FeSO^4·7H^2O,Fe(NO^3)^3·9H^2O,FeCl^3 and Fe^2O^12S^3 could oxide As(Ⅲ)to As(V).Among them,the proportion of As(Ⅲ)in FeCl^3 treated sludge decreased from 77.14%to 19.72%,and no obvious oxidation of As(Ⅲ)occurred in Fe(OH)^3,Fe^2O^3 and Al^2O^3 treated sludge.However,due to the strong reducibility of Na^2S·9H^2O,the proportion of As(Ⅲ)in Na^2S·9H^2O treated sludge increased to 85.84%.With the increase of the dosage of FeCl^3,cement or composite materials,the leaching amount of As in sludge decreased significantly.The As immobilization effect of FeCl^3 alone or FeCl^3+cement was better than that of cement alone.When the cement ratio was set to above 100%,FeCl^3-cement As immobilization effect was better than that of FeCl^3 alone.The As leaching concentrations of TCLP,H^2SO^4-HNO^3 and H^2O in 250%FeCl^3+125%cement treatment were reduced to the lowest values of 113.81,399.28 and 347.27 mg·L^-1,respectively,and As immobilization efficiency reached above 97%.This study can provide reference for the immobilization of high As-bearing sludge.