两种大型真菌子实体对Cd2+的生物吸附特性

对两种多孔菌科大型真菌槐栓菌(Trametes robiniophila)和木蹄层孔菌(Fomes fomentarius)子实体生物吸附Cd²⁺的影响因素(包括吸附剂用量、初始pH、吸附时间、初始Cd²⁺浓度)和吸附特性进行分析。结果表明,槐栓菌和木蹄层孔菌对低浓度的Cd²⁺(10 mg/L)吸附的最适pH为6;Cd²⁺的去除率随吸附剂用量和吸附时间的增加而增大,槐栓菌和木蹄层孔菌均在吸附剂用量为2g/L时达到吸附平衡,槐栓菌在吸附时间为30 min时达到吸附平衡,而木蹄层孔菌在吸附时间为60 min时达到吸附平衡;槐栓菌和木蹄层孔菌对10 mg/L Cd²⁺的最大去除率分别为98%和94%。Langmuir等温吸附平衡模型比Freundlich等温吸附平衡模型能更好的拟合两种大型真菌对Cd²⁺的吸附过程;槐栓菌和木蹄层孔菌对10 mg/L Cd²⁺的最大吸附量分别为17.40 mg/g和8.91 mg/g。对实验数据进行动力学模型拟合可知,两种大型真菌对Cd²⁺的生物吸附过程均符合准二阶动力学模型。槐栓菌和木蹄层孔菌生物吸附低浓度Cd²⁺的化学反应机理可能为离子交换。

Biosorption of Cd2+ using the fruiting bodies of two macrofungi

Discharge of heavy metals containing effluents into the water bodies contaminates the aqueous environment. This is one of the most serious environmental issues of the century. The conventional methods used for metal removal become less effective and more expensive when the volumes of wastewater are high, and the metal concentrations are low. Biosorption technology has gained important credibility during recent years because of its eco-friendly nature, excellent performance, and cost-effectiveness. Fruiting bodies of macrofungi are considered ideal for the biosorption of heavy metals, because it has been demonstrated that many fungal species exhibit high biosorptive potentials. Macrofungi grow prolifically and are found in many parts of the world. They are macro in size, tough in texture and have other physical characteristics conducive for their development as biosorbents without the need for immobilization or deployment of sophisticated reactor configuration as in the case of microorganisms. The aim of the present work was to evaluate the biosorption capacity of two different macrofungi, Trametes robiniophila and Fomes fomentarius in respect of heavy metals, viz. cadmium from aqueous solutions. The biosorption characteristics of Cd²⁺ from aqueous solution using the fruiting bodies of two macrofungi belonging to Polyporaceae (T. robiniophila and F. fomentarius) was investigated as a function of initial pH, biosorbent dosage, contact time, and initial Cd²⁺ concentration. The optimum initial pH of the aqueous solution was found to be 6.0 for the removal of low concentrations Cd²⁺ (10 mg/L). The percent removal of Cd²⁺ was found to increase with the increase in biosorbent dosage and contact time, and the biosorption of Cd²⁺ by two macrofungi all achieved equilibrium with biosorbent dosage of 2 g/L. The contact time achieved the biosorption equilibrium was 30 min for T. robiniophila and 60 min for F. fomentarius. Langmuir and Freundlich models are the most widely used models in the case of the adsorption of metal ions with biosorbents. Langmuir and Freundlich models were applied to describe the biosorption isotherm of Cd²⁺ by T. robiniophila and F. fomentarius. Langmuir model fitted the equilibrium data all better than the Freundlich isotherm for two macrofungi. The maximum biosorption capacities of T. robiniophila and F. fomentarius were found to be 17.40 and 8.91 mg/g, respectively, at optimum conditions of pH 6.0, contact time of 60 min and biosorbent dosage of 2 g/L. The prediction of biosorption rate gives important information for designing batch biosorption systems. Information on the kinetics of pollutant uptake is required for selecting optimum operating conditions for full-scale batch process. In order to clarify the biosorption kinetics of Cd²⁺ onto T. robiniophila and F. fomentarius fruiting bodies, two kinetic models, pseudo-first-order and pseudo-second-order models were applied to the experimental data. The results showed that the biosorption processes of Cd²⁺ by two macrofungi followed well pseudo-second-order kinetics. Chemical ion-exchange may be the main mechanism for the biosorption of Cd²⁺ by two macrofungi. Based on all results, it can also be concluded that T. robiniophila and F. fomentarius can be used as alternative biosorbent to treatment wastewater containing Cd²⁺ since they are low-cost biomass and have a considerable high biosorption capacity.