College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China; Key Laboratory of Plant Nutrition and the Agri‑environment in Northwest China, Ministry of Agriculture, Northwest A&F University, Yangling 712100, China.
State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Ministry of Water Resources, Yangling 712100, China; University of Chinese Academy of Sciences, Beijing 100049, China.
Sci Total Environ. 2022 May 1;819:152876. doi: 10.1016/j.scitotenv.2021.152876. Epub 2022 Jan 5.
Phosphate (P)-modified biochar is a good material for cadmium (Cd) immobilization, and the pore-forming effect of potassium ions (K) can favor the P loading on biochar. However, few studies have been done specifically on Cd(II) removal by composites of potassium phosphates with biochar, and the removal potential and mechanisms are not clear. Herein, apple tree branches, a major agricultural waste suitable for the development of porous materials, were pyrolyzed individually or together with KHPO, KHPO·3HO, or KPO·3HO to obtain biochars to remove Cd(II), denoted as pristine BC, BC-1, BC-2, and BC-3, respectively. The results showed that the orthophosphates containing more K enlarged the specific surface area, total pore volume and phosphorus loading of biochar. Co-pyrolysis of apple tree branches and P promoted the thermochemical transformation of P species. Only weak signal of orthophosphate was observed in the pristine BC, while the presence of orthophosphate, pyrophosphate and metaphosphate were detected in BC-1, and BC-2 and BC-3 showed the presence of orthophosphate and pyrophosphate. The maximum Cd(II) adsorption capacities of pristine BC, BC-1, BC-2 and BC-3 were 10.4, 88.5, 95.8, and 116 mg·g, respectively. Orthophosphate modification enhanced the Cd(II) adsorption capacity due to the formation of Cd-P-precipitates, namely Cd(PO)Cl, Cd(PO)OH, Cd(PO), CdPO, and Cd(PO). Furthermore, higher cation exchange efficiencies between Cd(II) and K in P-modified biochars also contributed to their high Cd(II) adsorption capacity. Cd(II) removal by BC-3 from artificially polluted water bodies showed more than 99.98% removal rates. Application of BC-3 also reduced the diethylene triamine pentaacetic acid-extracted Cd(II) in soil by 69.1%. The co-pyrolysis of apple tree branches and potassium phosphates shows great prospect in Cd(II) wastewater/soil treatment and provide a promising solution for agricultural waste utilization and carbon sequestration.
磷（P）改性生物炭是一种很好的固定镉（Cd）的材料，钾离子（K）的造孔效应有利于生物炭上的磷负载。然而，很少有研究专门针对磷酸钾与生物炭复合材料对 Cd(II)的去除，去除潜力和机制尚不清楚。在此，将苹果树枝，一种适合多孔材料开发的主要农业废物，单独或与 KHPO、KHPO·3HO 或 KPO·3HO 共热解，以获得分别表示为原始 BC、BC-1、BC-2 和 BC-3 的生物炭，以去除 Cd(II)。结果表明，含更多 K 的正磷酸盐扩大了生物炭的比表面积、总孔体积和磷负载量。苹果树与 P 的共热解促进了 P 物种的热化学转化。在原始 BC 中仅观察到弱的正磷酸盐信号，而在 BC-1 中检测到正磷酸盐、焦磷酸盐和偏磷酸盐，BC-2 和 BC-3 则显示出正磷酸盐和焦磷酸盐的存在。原始 BC、BC-1、BC-2 和 BC-3 的最大 Cd(II)吸附容量分别为 10.4、88.5、95.8 和 116 mg·g。正磷酸盐修饰由于形成了 Cd-P-沉淀物，如 Cd(PO)Cl、Cd(PO)OH、Cd(PO)、CdPO 和 Cd(PO)，从而增强了 Cd(II)的吸附能力。此外，P 改性生物炭中 Cd(II)与 K 之间的阳离子交换效率更高，也有助于其高 Cd(II)吸附容量。BC-3 从人为污染水体中去除 Cd(II)的去除率超过 99.98%。BC-3 的应用还降低了土壤中二乙烯三胺五乙酸提取的 Cd(II)69.1%。苹果树与钾磷酸盐的共热解在 Cd(II)废水/土壤处理方面具有广阔的前景，为农业废物利用和碳封存提供了一种有前途的解决方案。
