聚乙烯醇-海藻酸钠固定香菇废弃物吸附Pb和Cd的最佳配方

选用香菇废弃物作为生物吸附剂,用聚乙烯醇(PVA)-海藻酸钠(SA)同定香菇粉制成PVA-SA固定香菇,以吸附溶液中铅(Pb)和镉(Cd)的能力为主要评价指标,结合成球性、机械强度和耐酸性等,通过正交试验确定出吸附Pb的PVA-SA固定香菇最佳配方是8%PVA+1%SA+3%香菇粉+2%CaCl2的饱和H3BO3,对Pb的吸附率为95.4%,吸附Cd的PVA-SA同定香菇的最佳配方是5%PVA+1%SA+3%香菇粉+2%CaCl2的饱和H3BO3,对Cd的吸附率为63.7%.二小球的成球性、机械强度和耐酸性都较好.Langmuir等温吸附模型能最好地拟合香菇吸附Pb的热力学过程,相关系数R2达0.993 9;Freundlich模型能更好地描述香菇吸附Cd的热力学过程,R2为0.999 3.Freundlich等温吸附模型适合描述PVA-SA同定香菇吸附Pb和Cd的热力学过程,R2分别为0.958 7和0.982 3.自由香菇对Cd的理论最大吸附量qm-Langmuir (2.832 1 mg g-1)小于PVA-SA固定香菇的理论最大吸附量qm-Langmuir (6.447 5 mg g-1),自由香菇吸附Pb的Freundlich模型参数k(0.312 7)小于PVA-SA固定香菇吸附Pb的k(0.431 0),香菇固定后吸附Cd和Pb的能力有所提高.PVA-SA固定香菇吸附Pb和Cd的吸附平衡时间分别为3 h和7 h,比自由香菇吸附Pb和Cd的平衡时间(1 h)长.伪二级动力学模型能很好地拟合固定香菇吸附Pb和Cd的动力学过程,R2分别为0.999 9和0.994 6,由该模型计算出的对Pb和Cd的平衡吸附量理论值分别为0.453 6 mg g-1和0.2060 mg Cd g-1.伪二级动力学模型能很好地拟合同定香菇吸附Pb和Cd的动力学过程,由该模型计算出的固定香菇对Pb和Cd的平衡吸附量理论值分别为0.453 6 mg g-1和0.206 0 mg g-1,自由香菇对Pb和Cd的平衡吸附量理论值分别为1.817 2 mg g-1和0.842 5 mg g-1.PVA-SA固定香菇吸附Pb/Cd的伪二级动力学反应速率常数k2为1.324 1/1.253 1,自由香菇吸附Pb/Cd的k2为0.780 510.213 0,自由香菇吸附Pb/Cd的k2大于固定香菇的k2,表明固定香菇吸附Pb/Cd达到平衡所需要的时间比自由香菇所需要的时间长.图3表6参16

Optimal Condition of PVA- SA Immobilizing Lentinus edodes Residue for Absorbing Lead and Cadmium

In this study, Lentinus edodes residue was immobilized by polyvinyl alcohoI-Na-alginate (PVA-SA) for lead and cadmium biosorption. Based on the ability of absorbing lead and cadmium from aqueous solution, the mechanical strength and bailing property, an orthogonal experiment was done to confirm the optimal condition of PVA-SA immobilizing L. edodes. The optimal immobilization condition for absorbing lead was 8% (m/V) PVA + 1% sodium alginate + 3% L. edodes + 2% CaCl_2 saturated boric acid solution, with biosorption rate of 95.4%, while that for absorbing cadmium were 5% PVA + 1% SA + 3% L. edodes + 2% CaCl_2, with biosorption rate of 63,7%. Langmuir model best described free L. edodes Pb_(2+) biosorption isotherm, with R~2 0.993 9. Freundlich model best fitted free L.edodes Cd~(2+) biosorption isotherm, with R~2 0.999 3. Freundlich model best fitted Pb~(2+) and Cd~(2+) isotherm biosorption process by PVA- SA immobilizing L. edodes, with R~2 0.958 7 and 0.982 3, respectively. The theoretic maximum biosorption quantities q_((Cd-m-Langmuir,free)) 2.832 1< q_((m-Langmuir, immobilization)) 6.447 5 indicated after immobilizing treatment, capacity of L. edodes for Cd_(2+) biosorption increased. K_((Pb-Freundlich,free)) 0.312 7