Yuan Qiusheng, Wang Peifang, Wang Xun, Hu Bin, Wang Chao, Xing Xiaolei
Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, Jiangsu 210098, PR China.
Key Laboratory of Integrated Regulation and Resources Development on Shallow Lakes, Ministry of Education, College of Environment, Hohai University, Nanjing, Jiangsu 210098, PR China.
Sci Total Environ. 2023 Mar 20;865:161097. doi: 10.1016/j.scitotenv.2022.161097. Epub 2022 Dec 29.
Cadmium (Cd) contamination in rivers or lakes has attracted worldwide concerns. Biochar pyrolyzed form crop residues (CR) could adsorb Cd(II) from aquatic environments, while the removal capacity of single CR biochar is relatively low. Nano-chlorapatite (nClAP) modification can enhance metal scavenging ability, but little is known about the behaviors and mechanisms of Cd(II) adsorption by nClAP-modified CR biochars. In this study, the influences of feedstock type, pyrolysis temperature, nClAP modification and aquatic environments on Cd(II) adsorption of biochars derived from rice (RB) and wheat (WB) husks were investigated comprehensively. Results showed that the pristine RB and WB showed low and similar Cd(II) adsorption capacities, while the rise of pyrolysis temperatures from 300 to 600 °C significantly improved the adsorption capacities. The Cd(II) adsorption of both RB and WB was regarded as monolayer chemical processes controlled by chemical precipitation, surface complexation and cation exchange mechanisms. Moreover, the nClAP modification notably enhanced Cd(II) adsorption capacities from 13.2 to 39.9 mg·g of pristine biochars to 25.2-60.7 mg·g of modified biochars attributed to the improved contribution of Cd(II)-phosphate precipitation. Among all biochars, the nClAP-modified RB and WB pyrolyzed at 500 °C had the highest Cd(II) adsorption capacities with 60.7 and 48.3 mg·g, respectively. These biochars could maintain good adsorption performances under the neutral-alkaline (pH 6-8), low ionic strength, high dissolved organic matter and all oxidation-reduction potential conditions. In conclusion, this study reveals the importance of nClAP modification to optimize Cd(II) adsorption of CR biochars, which provides a promising future for its practical application in aquatic Cd(II) scavenging.
河流或湖泊中的镉（Cd）污染已引起全球关注。由农作物秸秆（CR）热解制备的生物炭能够从水环境中吸附Cd（II），但单一CR生物炭的去除能力相对较低。纳米氯磷灰石（nClAP）改性可以增强金属清除能力，但关于nClAP改性CR生物炭对Cd（II）的吸附行为和机制知之甚少。本研究全面考察了原料类型、热解温度、nClAP改性及水环境对水稻（RB）和小麦（WB）秸秆生物炭吸附Cd（II）的影响。结果表明，原始的RB和WB对Cd（II）的吸附能力较低且相近，而热解温度从300℃升高到600℃显著提高了吸附能力。RB和WB对Cd（II）的吸附均被认为是由化学沉淀、表面络合和阳离子交换机制控制的单层化学过程。此外，nClAP改性显著提高了Cd（II）的吸附能力，原始生物炭的吸附量为13.2至39.9 mg·g，改性生物炭的吸附量为25.2至60.7 mg·g，这归因于Cd（II）-磷酸盐沉淀作用的增强。在所有生物炭中，500℃热解的nClAP改性RB和WB对Cd（II）的吸附能力最高，分别为60.7和48.3 mg·g。这些生物炭在中性至碱性（pH 6-8）、低离子强度、高溶解有机物和各种氧化还原电位条件下都能保持良好的吸附性能。总之，本研究揭示了nClAP改性对优化CR生物炭吸附Cd（II）的重要性，为其在水体Cd（II）清除中的实际应用提供了广阔前景。
