磁性生物炭对重金属污染废水处理条件优化及机理

Optimization and the mechanismin treatment of heavy metals wastewater with magnetic biochar

将水稻谷壳经改性和负磁后制得磁性谷壳生物炭(BC-Fe),通过正交实验研究了pH、生物炭添加量、吸附时间和转速对磁性谷壳生物炭吸附实际污染废水中Cd^(2+)和Zn^(2+)的影响,提出了磁性谷壳生物炭作为实际污染废水处理材料的最佳操作条件,并应用于多步骤废水处理系统中,同时进行了BC-Fe的再生吸附实验.正交实验结果表明,在pH为6.0、固液比为6.0 g·L^(-1)、吸附时间为1.0 h、转速为160 r·min^(-1)的条件下,磁性谷壳生物炭对Cd^(2+)和Zn^(2+)的去除率最高,分别达到61.1%和60.4%,吸附量分别为8.6 mg·g^(-1)和21.3 mg·g^(-1).在实验所设条件下,Cd^(2+)和Zn^(2+)的综合去除效果随着pH和生物炭添加量的增加而显著升高,吸附时间和转速的影响未达显著水平.在多步骤废水处理系统中,使用CaO和Na_2S作为前处理,利用磁性谷壳生物炭二次处理,可使实际污染废水中Cd^(2+)、Zn^(2+)、Pb^(2+)、Mn^(2+)、Fe^(2+)的去除率分别达到100%、99.8%、99.3%、97.8%、100%,SS降为1.0 mg·L^(-1),此时系统pH为7.5,色度为2倍,出水各项指标均达到硫酸工业污染物排放标准(GB 26132—2010)和污水综合排放标准(GB 8978—1996)的要求.再生实验表明,BC-Fe第3次吸附Cd^(2+)和Zn^(2+)的去除率分别为50.6%和49.1%,吸附材料再生性能良好.

In order to study the effects of magnetic biochar （BC-Fe, made from rice husks） on the adsorption of Cd2＋ and Zn2＋ in practical heavy metals wastewater, the solution pH, dosage, adsorption time, and rotation rate were investigated by means of an orthogonal experiment. Meanwhile, the optimal operating conditions for practical wastewater treatment were put forward using BC-Fe as a material in a multi-step wastewater treatment system, and the regeneration experiment of BC-Fe was also investigated. The results in orthogonal experiment show that at the optimal condition of solution pH 6, solid- liquid ratio 6 g＇L-~ , adsorption time 1 hour, and rotation rate 160 r.min-1 , the maximal removal rates were 61.1% for Cd2＋ and 60.4% for Zn^2＋ , and the maximal adsorptive capacities were 8.6 mg. g-1 for Cd2＋ and 21.3 mg. g^-1 for Zn^2＋ after applying BC-Fe, respectively. Within the experiment conditions, the removal efficiencies of two metal ions increased significantly with the increase of solution pH and BC-Fe dosage, but insignificant for adsorption time and rotation rate. In the multi-step wastewater treatment system, using CaO and Na2S as pre-treatment materials and BC-Fe as a deeply purifying treatment material, the removal rates were 100%, 99.8%, 99.3%, 97.8%, 100%, for Cd^2＋ , Zn^2＋ , Pb^2＋ , Mn^2＋, and Fe^2＋ , respectively. Meanwhile, the suspended solid decreased to 1 mg＇L-1 , the solution pH reached 7.5, and the chromaticity decreased to 2, respectively. The treated wastewater met the Emission National Standard of Pollutants for Sulfuric Acid Industry （GB 26132--2010） and the Emission National Standard for Integrated Wastewater （GB 8978--1996）. Additional, the regeneration experimental results show that the removal efficiencies of Cd^2＋ and Zn^2＋ were 50.6% and 49.1% after applying BC-Fe even after recycled for three times.