共热解法制备方解石/生物炭复合材料及其吸附Pb(II)性能和机制

为了制备一种高效吸附含Pb(II)废水的生物炭材料，以椰壳(CS)和方解石(CAL)为原料，采用共热解法分别在500℃、600℃、700℃制备了方解石/生物炭(CAL/BC)复合材料。通过SEM、ICP-MS、BET、XRD、FTIR等方法对CAL/BC复合材料的表面微观形态和结构进行了表征。结果发现，三种热解温度条件下，CAL均能够与CS紧密结合，而且CAL/BC具有较大的比表面积，表面含有丰富的官能团。批量吸附实验结果表明，CAL和CS质量比为1∶2，pH值为5.5，吸附剂添加量为1.5 g·L?1，此时CAL/BC复合材料对Pb(II)的吸附量分别为95.24 mg·g?1(500℃)、99.01 mg·g?1(600℃)、185.19 mg·g?1(700℃)，可见热解温度为700℃时，吸附效果最佳。吸附过程符合二级动力学模型和Langmuir等温线模型。CAL/BC复合材料吸附Pb(II)的主要机制是沉淀、离子交换、阳离子-π作用、孔隙填充和静电引力。此外，CAL/BC复合材料在4次吸附-解吸循环后仍能保持较高的Pb(II)去除率。因此，共热解法制备的CAL/BC复合材料在处理废水中的Pb(II)方面具有广阔的应用前景。 

Preparation of calcite/biochar composite by co-pyrolysis and its adsorption properties and mechanism for Pb(II)

In order to obtain a biochar material which adsorbs PB (II) in wastewater efficiently, calcite/biochar (CAL/BC) composite was prepared by co-pyrolysis at 500℃, 600℃ and 700℃, using coconut shell (CS) and calcite (CAL) as raw materials. The surface morphology and structure of CAL/BC composites were characterized by SEM, ICP-MS, BET, XRD and FTIR. The results show that CAL and CS combine tightly under the three pyrolysis tempera-tures, and CAL/BC has a large specific surface area and a large number of functional groups. The maximum adsorption capacities of PB (II) on CAL/BC composite (CAL∶ CS=1∶ 2, mass ratio) prepared at 500℃, 600℃, and 700℃ are 95.24 mg·g?1, 99.01 mg·g?1, and 185.19 mg·g?1. The optimum adsorption condition is pH=5.5 and the amount of adsorbent is 1.5 g·L?1. The adsorption process conforms to the second-order kinetic model and Langmuir isotherm model. The mechanisms of adsorption of Pb(II) on CAL/BC composites are precipitation, ion exchange, cation-π action, pore filling and electrostatic gravitation. In addition, the removal rate of Pb(II) by CAL/BC composite remains high level after 4 adsorption-desorption cycles. Therefore, the CAL/BC composite prepared by co-pyrolysis has a excellent application prospect in the treatment of Pb(II) in wastewater.