酸性条件下饱和多孔介质中赤铁矿胶体和Cr(Ⅵ)的协同运移及影响机制

Co-transport and influence mechanism of hematite colloids and Cr(Ⅵ) in saturated porous media under acidic conditions

含铬污泥的长时间填埋堆存可能对周边环境带来污染风险.制革污泥中富含胶体物质和腐殖酸,有研究表明腐殖酸能通过吸附和静电作用影响胶体和Cr(Ⅵ)在多孔介质中的协同运移,使Cr(Ⅵ)向深层环境介质迁移.然而,制革污泥中赤铁矿胶体等共存物质对Cr(Ⅵ)运移的影响尚不清楚.本研究选取制革污泥中特征组分(赤铁矿胶体和腐殖酸),通过吸附实验和柱迁移实验等方法模拟酸性条件下,腐殖酸和Cr(Ⅵ)浓度对赤铁矿胶体稳定性和运移行为,探究赤铁矿胶体协同Cr(Ⅵ)运移的环境风险.结果表明,赤铁矿胶体对Cr(Ⅵ)的最大吸附量为2.72 mg·g^(−1);Cr(Ⅵ)浓度越高,赤铁矿胶体聚集越明显,腐殖酸能够有效抑制Cr(Ⅵ)-赤铁矿胶体聚集,使Cr(Ⅵ)-赤铁矿胶体在石英砂柱中的穿透量增加,增强了Cr(Ⅵ)-赤铁矿胶体悬浮液的稳定性,提高了赤铁矿胶体携带Cr(Ⅵ)的运移能力.基于DLVO理论,综合柱流出物的zeta电位和颗粒尺寸的演变规律,揭示了Cr(Ⅵ)、赤铁矿胶体和腐殖酸在二元和三元体系中协同运移的作用机理.研究结果将为评估制革污泥中的赤铁矿胶体在实际环境中携带Cr(Ⅵ)运移的风险提供理论支持.

Long-term landfill storage of chrome-containing sludge may cause pollution risks to the surrounding environment.Tanning sludge contains abundant colloidal substances and humic acid.Studies have shown that humic acid can affect the co-transport of colloid and Cr(Ⅵ)in porous media through adsorption and electrostatic interaction,causing Cr(Ⅵ)transport to deep underground environment.However,the effect of coexisting substances such as hematite(Hem)colloids in tannery sludge on the transport of Cr(Ⅵ)remains unclear.In this study,the characteristic components(Hem colloids and humic acid(HA))in tannery sludge were selected to simulate the effects of HA and Cr(Ⅵ)concentration on the stability and transport behavior of Hem colloids under acidic conditions through adsorption and column transport experiments,exploring the environmental risk of Cr(Ⅵ)-Hem colloids co-transporting.The results showed that the maximum adsorption of Cr(Ⅵ)by Hem colloids was 2.72 mg·g^(-1);the higher the concentration of Cr(Ⅵ),the more obvious the aggregation of Hem colloids.However,HA effectively inhibited the aggregation of Cr(Ⅵ)-Hem colloid,therefore increased their penetration in quartz sand columns and enhanced the transport capacity of Hem colloids carrying Cr(Ⅵ).The co-transport mechanisms of Cr(Ⅵ),Hem colloids and HA in binary and ternary systems were comprehensively revealed by evaluating the evolution of zeta potential and particle size of the column effluent as well as DLVO theoretical calculations.The results will provide theoretical support to evaluate the risk of Cr(Ⅵ)transport being carried by Hem colloids in tannery sludge under the real-life situation.