Department of Geotechnical Engineering, São Carlos School of Engineering, University of São Paulo, 400 Trabalhador São Carlense Ave., 13566-590, São Carlos, Brazil; GeoBioTec, Department of Geoscience, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal.
GeoBioTec, Department of Geoscience, University of Aveiro, Campus de Santiago, 3810-193, Aveiro, Portugal.
Environ Res. 2022 Mar;204(Pt A):111988. doi: 10.1016/j.envres.2021.111988. Epub 2021 Sep 1.
The historic contamination of water and soils by arsenic (As) is an extremely alarming environmental and public health issue worldwide. This study investigated the relationship between As sorption and physicochemical properties of composts and biochars derived from the organic fraction of municipal solid wastes (OFMSW) towards the development of promising sorbents with value-added solid wastes management solutions. The sorbents were characterized and their effectiveness on the As sorption was tested. Several isothermal and kinetic sorption models were used for the prediction of sorption. Composts did not show promising sorption capacities, and in some cases, the As immobilization was practically null. In contrast, biochars achieved higher sorption performance, and the experimental data fitted well on Dubinin-Rabushkevich and Langmuir models, with higher R values. The maximum sorption capacities of BC700 estimated by such models were 6.495 and 170.252 mg g, respectively, whereas those of BC500 estimated by D-R and Langmuir models were only 0.066 and 0.070 mg g, respectively. In sorption kinetics, As was retained onto biochars at a faster first stage, reaching equilibrium after approximately 1 h and 2 h for initial concentrations of 10 and 100 mg L. The pseudo-second-order, Ritchie's second-order, Ritchie's, and Elovich models more adequately described the sorption kinetics of As onto biochars with high R values. Overall, the complexation and precipitation were predominant mechanisms for As sorption by OFMSW-derived biochars. Furthermore, the mathematical models indicated contributions arise from physisorption and external and internal diffusion mechanisms. Although BC700 can immobilize large As amounts, the gastric phase of the oral bioaccessibility test revealed more than 80% of the sorbed As could be released under conditions similar to a human stomach (pH~1.2). Such conclusions have given important insights about the refining of effective and eco-friendly remediation technologies for the management and rehabilitation of As-contaminated soil and water, particularly in developing countries.
砷（As）对水和土壤的历史性污染是一个极其令人震惊的全球环境和公共卫生问题。本研究调查了来自城市固体废物有机部分（OFMSW）的堆肥和生物炭的理化性质与砷吸附之间的关系，以期开发具有附加值的固体废物管理解决方案的有前途的吸附剂。对吸附剂进行了表征，并测试了它们对砷吸附的有效性。使用了几种等温线和动力学吸附模型来预测吸附。堆肥没有表现出有希望的吸附能力，在某些情况下，砷的固定实际上是无效的。相比之下，生物炭实现了更高的吸附性能，实验数据很好地符合 Dubinin-Rabushkevich 和 Langmuir 模型，具有更高的 R 值。通过这些模型估算的 BC700 的最大吸附容量分别为 6.495 和 170.252 mg/g，而通过 D-R 和 Langmuir 模型估算的 BC500 的最大吸附容量仅分别为 0.066 和 0.070 mg/g。在吸附动力学方面，As 在生物炭上的保留速度较快，在初始浓度为 10 和 100 mg/L 时，约 1 小时和 2 小时后达到平衡。准二级、Ritchie 二级、Ritchie 方程和 Elovich 方程更能准确描述 As 吸附到生物炭上的动力学。总体而言，络合和沉淀是 OFMSW 衍生生物炭吸附 As 的主要机制。此外，数学模型表明，吸附过程涉及物理吸附和外部扩散及内部扩散机制。尽管 BC700 可以固定大量的 As，但口服生物可利用性测试的胃相表明，在类似于人类胃（pH~1.2）的条件下，超过 80%的吸附 As 可以释放出来。这些结论为开发有效的、对环境友好的修复技术提供了重要的见解，用于管理和修复受 As 污染的土壤和水，特别是在发展中国家。
