Guangdong Industrial Contaminated Site Remediation Technology and Equipment Engineering Research Center, School of Environmental Science and Engineering, Guangdong University of Technology, Guangzhou, 510006, PR China; College of Natural Resources and Environment, South China Agricultural University, Guangzhou, 510642, PR China.
College of Natural Resources and Environment, South China Agricultural University, Guangzhou, 510642, PR China.
Environ Pollut. 2021 Apr 15;275:116485. doi: 10.1016/j.envpol.2021.116485. Epub 2021 Jan 13.
Magnetic biochars were prepared by chemical co-precipitation of Fe/Fe onto rice straw (M-RSB) and sewage sludge (M-SSB), followed by pyrolysis treatment, which was also used to prepare the corresponding nonmagnetic biochars (RSB and SSB). The comparison of adsorption characteristics between magnetic and nonmagnetic biochars was investigated as a function of pH, contact time, and initial Cd concentration. The adsorption of nonmagnetic biochars was better described by pseudo-second-order kinetic model, and the adsorption of RSB and SSB was better described by Langmuir and Freundlich models, respectively. Magnetization of the biochars did not change the applicability of their respective adsorption models, but reduced their adsorption capabilities. The maximum capacities were 42.48 and 4.64 mg/g for M-RSB and M-SSB, respectively, underperforming their nonmagnetic counterparts of 58.65 and 7.22 mg/g for RSB and SSB. Such a reduction was fundamentally caused by the decreases in the importance of cation-exchange and Cπ-coordination after magnetization, but the Fe-oxides contributed to the precipitation-dependent adsorption capacity for Cd on magnetic biochars. The qualitative and quantitative characterization of adsorption mechanisms were further analyzed, in which the contribution proportions of cation-exchange after magnetization were reduced by 31.9% and 12.1% for M-RSB and M-SSB, respectively, whereas that of Cπ-coordination were reduced by 3.4% and 31.1% for M-RSB and M-SSB, respectively. These reductions suggest that for adsorbing Cd the choice of conventional biochar was more relevant than whether the biochar was magnetized. However, magnetic biochars are easily separated from treated solutions, depending largely on initial pH. Their easy of separation suggests that magnetic biochars hold promise as more sustainable alternatives for the remediation of moderately Cd-contaminated environments, such as surface water and agriculture soil, and that magnetic biochars should be studied further.
磁性生物炭是通过化学共沉淀法将 Fe/Fe 负载到稻草（M-RSB）和污水污泥（M-SSB）上，然后进行热解处理而制备的，也用于制备相应的非磁性生物炭（RSB 和 SSB）。研究了 pH、接触时间和初始 Cd 浓度等因素对磁性和非磁性生物炭吸附特性的影响。非磁性生物炭的吸附更符合准二级动力学模型，而 RSB 和 SSB 的吸附更符合 Langmuir 和 Freundlich 模型。生物炭的磁化并没有改变其各自吸附模型的适用性，但降低了它们的吸附能力。M-RSB 和 M-SSB 的最大吸附容量分别为 42.48 和 4.64mg/g，低于 RSB 和 SSB 的 58.65 和 7.22mg/g。这种降低主要是由于磁化后阳离子交换和 Cπ-配位的重要性降低，但 Fe-氧化物有助于 Cd 在磁性生物炭上的沉淀依赖吸附能力。进一步分析了吸附机制的定性和定量特征，其中 M-RSB 和 M-SSB 的阳离子交换贡献比例分别降低了 31.9%和 12.1%，而 Cπ-配位的贡献比例分别降低了 3.4%和 31.1%。这些降低表明，对于吸附 Cd，选择传统生物炭比生物炭是否磁化更为重要。然而，磁性生物炭很容易从处理后的溶液中分离出来，这主要取决于初始 pH。它们易于分离表明，磁性生物炭作为修复中度 Cd 污染环境（如地表水和农业土壤）的更可持续替代品具有很大的潜力，应该进一步研究磁性生物炭。
