水洗处理对秸秆生物质炭吸附解吸Cd2+和Pb2+的特性影响

水洗处理在不影响生物质炭性质的前提下，可以去除附着在其表面的热解副产物，从而保证对重金属离子的去除能力。以小麦和玉米秸秆为原料，比较两种秸秆类生物质炭对溶液Cd2+和Pb2+的吸附解吸特点及其水溶性盐分含量的影响。结果表明，小麦和玉米秸秆生物质炭对Cd2+和Pb2+的吸附过程均更好地符合准二级动力学方程和Langmuir方程。小麦秸秆生物质炭对Cd2+和Pb2+的最大吸附量达12.82 mg g?1和9.91 mg g?1，为玉米秸秆吸附量的1.31 ~ 1.76倍和1.06 ~ 1.53倍。洗脱水溶性盐分可以降低生物质炭对Cd2+和Pb2+的吸附，水洗后小麦秸秆和玉米秸秆生物质炭对Cd2+的最大吸附量分别降低42.36%和60.13%，对Pb2+的最大吸附量分别降低29.47%和62.72%。水洗处理提高了两种秸秆生物质炭对Cd2+和Pb2+的解吸率，其中小麦秸秆生物质炭提高幅度较大，由原来对Cd2+的解吸率为1.84% ~ 13.05%提高到7.88% ~ 20.19%，对Pb2+的解吸率为1.57% ~ 11.82%提高到6.34% ~ 16.94%。因此，可溶性盐分在秸秆生物质炭吸附Cd2+和Pb2+的过程中具有重要作用，该研究结果将为制备高效修复重金属污染土壤的生物质材料提供技术支撑。

Effects of Water Washed Biochar Types Derived from Different Straw Materials on the Adsorption/Desorption of Cd2+ and Pb2+

Water washing could remove the pyrolysis by-products attached to the surface of biochar when the biochar properties remained unchanged, which would ensure the removal ability of heavy metal. The adsorption and desorption characteristics of Cd2+ and Pb2+ and the soluble salt contents by different biochar types derived from wheat and rice straw were compared in this study. Results showed that the adsorption processes of Cd2+ and Pb2+ by biochar were better fitted a pseudo second order kinetic model and a Langmuir equation. The maximum adsorption capacities of biochar from wheat straw on Cd2+ and Pb2+ were 12.82 mg g?1 and 9.91 mg g?1, which were 1.31-1.76 and 1.06-1.53 times than that from rice straw. Removing soluble salt with water washing decreased the adsorption capacities of Cd2+ and Pb2+ by biochar. After water washing, the maximum adsorption capacities of biochar derived from wheat and rice straw on Cd2+ decreased by 42.36% and 60.13%, and the sorption capacities on Pb2+ decreased by 29.47% and 62.72%. However, the desorption rates of Cd2+ and Pb2+ were higher by biochar from wheat straw than that from rice straw. The maximum desorption rates of the un-washed biochar on Cd2+ and Pb2+ were 1.84%-13.05% and 1.57%-11.82%, while those of the washed biochar were 7.88%-20.19% and 6.34%-16.94%, respectively. Therefore, water soluble salts in biochar play an important role in the adsorption/desorption of Cd2+ and Pb2+. These results would provide technical support to prepare biomass materials for remediation of heavy metal contaminated soil.