Abstract Hydrochar is a promising adsorbent for the removal of heavy metals, but the low surface area limits the removal efficiency and practical application. Therefore, improving the surface area of the hydrochar is critical to increasing the adsorbent removal. In this study, the ultrasonic pretreatment of biomass (10‒30 min) and CaO addition (5‒15%) were adopted to assist the hydrothermal carbonization (HTC) of granatum at 220°C. The properties of the modified hydrochar and the removal efficiency for Pb2+ in the aqueous solution were investigated. Results showed that the porosity of hydrochar was obviously improved by the CaO addition, and the largest surface area of 21.86 m2·g−1 was obtained during HTC with 15% CaO addition. Meanwhile, the functional groups of ‒OH and C═O increased and the pH of the hydrochar increased from weakly acidic to alkaline by CaO addition. The Pb2+ adsorption capacity of raw hydrochar was 10.03 mg·g−1, and it was enhanced by 80.76‒171.58% after CaO addition. The ultrasonic pretreatment of granatum had little effect on the characteristics of hydrochar except to improve the surface area from 8.27 to 9.06 m2·g−1, resulting in a 1.30‒6.78% increase in the adsorption capacity.

中文翻译：

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添加氧化钙和超声预处理辅助石榴水热炭化吸附铅

摘要 水炭是一种很有前途的重金属去除吸附剂，但其比表面积小限制了去除效率和实际应用。因此，提高水炭的表面积对于提高吸附剂的去除率至关重要。本研究采用生物质超声预处理（10-30 min）和CaO添加（5-15%）辅助石榴在220℃的水热碳化（HTC）。研究了改性水炭的性质和对水溶液中Pb2+的去除效率。结果表明，CaO的加入显着提高了水炭的孔隙率，在加入15% CaO的HTC过程中获得了21.86 m2·g-1的最大比表面积。同时，CaO的加入使-OH和C=O的官能团增加，水炭的pH值由弱酸性变为碱性。原料水炭对Pb2+的吸附量为10.03 mg·g-1，添加CaO后吸附量提高了80.76-171.58%。超声波预处理对水炭的特性影响不大，只是将比表面积从8.27提高到9.06 m2·g-1，吸附量提高了1.30-6.78%。