Li Su, Tian Zhuang, Liu Ronghui, Zhou Wenbo, Cheng Haina, Sun Jianxing, Zhao Kaifang, Wang Yuguang, Zhou Hongbo
School of Minerals Processing and Bioengineering, Central South University Changsha Hunan 410083 China
Key Laboratory of Biometallurgy of Ministry of Education, Central South University Changsha 410083 China.
RSC Adv. 2020 Jan 8;10(3):1388-1399. doi: 10.1039/c9ra08267k. eCollection 2020 Jan 7.
Plant incineration ash is the final product from the remediation of multi-metal contaminated soils by the phytoextraction process. The content of heavy metals in plant ash was found to be higher than the regulatory criteria and it was thus classified as hazardous waste. So far, no eco-friendly and cost-effective technology has been developed for the management of this residue. Herein, a cleaner strategy of bioleaching combined with brine leaching of multi-metals from plant ash was developed. The bioleaching results indicated that 88.7% (Zn), 93.2% (Cd), 99.9% (Mn) and 13.8% (Pb) were achieved under optimum conditions of Fe(ii) concentration 6.0 g L, pH 1.8 and pulp density 15% (w/v). Subsequently, the introduction of brine leaching using 200 g L NaCl significantly increased Pb recovery to 70.6% under conditions of 15% (w/v) pulp density, thereby ultimately achieving deep recovery of all metals. An investigation of the mechanism revealed that H attack and microorganisms were the dominant mechanism for bioleaching of Zn, Cd and Mn, and the bioleaching kinetics of Zn in ash were controlled by interface mass transfer and diffusion across the product layer. Risk assessment tests indicated that the leached residues could pass the TCLP test standard and be safely reused as nonhazardous materials. These findings demonstrated that the two-stage leaching strategy was feasible and promising for multi-metal removal from plant ash.
植物焚烧灰是植物提取法修复多金属污染土壤的最终产物。研究发现，植物灰中的重金属含量高于监管标准，因此被归类为危险废物。到目前为止，尚未开发出用于处理这种残渣的环保且具有成本效益的技术。在此，开发了一种从植物灰中生物浸出与盐水浸出相结合的多金属清洁策略。生物浸出结果表明，在Fe(ii)浓度6.0 g/L、pH 1.8和矿浆密度15% (w/v)的最佳条件下，锌的浸出率达到88.7%，镉为93.2%，锰为99.9%，铅为13.8%。随后，在矿浆密度15% (w/v)的条件下，引入200 g/L NaCl的盐水浸出显著提高了铅的回收率，达到70.6%，从而最终实现了所有金属的深度回收。机理研究表明，H攻击和微生物是锌、镉和锰生物浸出的主要机制，灰中锌的生物浸出动力学受界面传质和产物层扩散控制。风险评估测试表明，浸出残渣可以通过TCLP测试标准，并作为非危险材料安全再利用。这些结果表明，两阶段浸出策略对于从植物灰中去除多金属是可行且有前景的。
