改性污泥基生物炭的性质与重金属吸附效果

Characteristics and Heavy Metal Adsorption Performance of Sewage Sludge-derived Biochar from Co-pyrolysis with Transition Metals

为提高污泥基生物炭在高钙溶液体系中对重金属阳离子的吸附能力,将Fe_2O_3、MnO_2、ZnO与市政污泥以质量比1∶10(以过渡金属元素质量计)混合共热解,制备改性生物炭;表征改性生物炭的组成、官能团分布和表面性质,考察其对典型重金属阳离子Cd^(2+)的吸附效果.过渡金属氧化物可促进污泥的热解,改性生物炭的H/C原子比均低于0. 31,碳链裂解脱氢更彻底.改性生物炭中Fe、Mn保留较好,分别主要以单质和氧化物形态存在;而Zn流失较多.改性生物炭中的孔隙以介孔为主,平均孔径约3. 8 nm,比表面积在50 m^2·g^(-1)以上.初始浓度约200 mg·L^(-1)的Cd^(2+)溶液中,Ca^(2+)初始浓度从0 mg·L^(-1)升高到约200 mg·L^(-1),Fe改性生物炭对Cd^(2+)的吸附容量从43. 17 mg·g^(-1)降至27. 88 mg·g^(-1),但仍较未改性生物炭高10 mg·g^(-1)以上,在含钙溶液体系中表现出了对Cd^(2+)更强的吸附性能. Fe_2O_3较MnO_2和ZnO对市政污泥基生物炭吸附重金属的强化效果更好.

To enhance the heavy metal cation adsorption capacity of sewage sludge-derived biochar in an aqueous medium with a high concentration of Ca2+, modified biochars were obtained from co-pyrolysis of sewage sludge and transition metal oxides (with a sewage sludge:transition metal mass ratio of 10:1), such as Fe2O3, MnO2, and ZnO. The properties of the modified biochars were characterized, and the Cd^2+ adsorption effect of the modified biochars was determined as well. The H/C atom ratios of the modified biochars were all lower than 0.31, indicating that the transition metal oxides catalyzed the decomposition and volatilization of organic matter in sewage sludge. The majority of the added Fe and Mn remained in the modified biochars, and existed as a simple substance and oxide, respectively;while significant loss of Zn occurred. The pores of the modified biochars were mainly mesopores with an average pore size of approximately 3.8 nm, and the specific surface area of the modified biochars was larger than 50 m2·g^-1. When the initial Cd2+ concentration was increased from 0 mg·L^-1 to approximately 200 mg·L-1, the Cd^2+ adsorption capacity of the Fe-modified biochar declined from 43.17 mg·g^-1 to 27.88 mg·g^-1, which was still higher than that of the unmodified biochar by at least 10 mg·g^-1. In aqueous media with a high concentration of Ca^2+, the Fe-modified biochar showed better Cd2+ adsorption performance;thus, compared to MnO2 and ZnO, Fe2O3 was the best choice to enhance the heavy metal adsorption performance of the sewage sludge-derived biochar.