生物炭-膨润土共改性及其铅离子吸附与稳定化研究

重金属污染具有高毒性、持久存留和生物积累等特性, 严重危害人体健康和生态安全。本研究通过氯化钙对玉米芯残渣和膨润土混合物进行碱改性, 在无氧条件下高温煅烧制备了一种碱改性生物炭-膨润土复合物(CaO-Bent-CB)。该复合物的比表面积高, 达到441.1 m²/g, 明显高于直接煅烧制备的生物碳(132.7 m²/g)和碱改性生物炭(177.2 m²/g)。进一步评价了该复合物对水中铅离子吸附性能, 结果表明在水中铅离子浓度为120 mg/L, 膨润土与玉米芯残渣质量比为1:5, 用量为1 g/L条件下, 吸附6 h后铅离子去除率达98%, 吸附量为109.6 mg/g, 均高于生物炭(13.4 mg/g)、膨润土(72.9 mg/g)和碱改性生物炭(86.9 mg/g)。此外, 采用CaO-Bent-CB对铅离子污染土壤进行稳定化处理, 当土壤中铅离子浓度为2200 mg/kg, CaO-Bent-CB用量为土壤干重的8%时, 在pH=3.2的硫酸-硝酸浸提液中浸出12 h, 酸浸出铅离子浓度低至4.5 mg/L, 低于危险废物鉴别标准值(5 mg/L)。上述研究结果表明这种生物炭-膨润土共改性复合物在重金属污染水体和土壤修复中具有很好的应用前景。

Co-modification of Biochar and Bentonite for Adsorption and Stabilization of Pb2+ ions

Heavy metals can seriously endanger human health and the ecological environment due to their toxicity, persistence, and bioaccumulative nature. In this study, an alkali-modified biochar-bentonite composite (CaO-Bent-CB) was prepared by alkali modification of corncob residues and bentonite mixture by calcium chloride and calcination at high temperature under anaerobic conditions. The CaO-Bent-CB composite has a specific surface area of ​​441.1 m²/g, which is significantly higher than CB (132.7 m²/g) and CaO-CB (177.2 m²/g). Meanwhile, the adsorption perfermance of CaO-Bent-CB to lead ions in water was evaluated. The results showed that the removal efficiency reached 98% after 6 h-adsorption, and the adsorption capacity was 109.6 mg/g when the concentration of lead ion was 120 mg/L, the weight ratio of bentonite to corncob residues was 1:5, and the dosage was 1 g/L. The adsorption capacity of CaO-Bent-CB was higher than that of CB (13.4 mg/g), bentonite (72.9 mg/g) and CaO-CB (86.9 mg/g). Moreover, the lead ion contaminated soil was stabilized by CaO-Bent-CB. When the concentration of lead ion in soil is 2200 mg/kg, and the loading of CaO-Bent-CB is 8% of soil, the concentration of lead ions in acid leachate (H₂SO₄-HNO₃, pH=3.2, 12 h-soaking) is 4.5 mg/L, which is lower than the standard value of hazardous waste identification (5 mg/L). The results show that CaO-Bent-CB has a great potential in the water treatment and heavy metals removal in soil.