Single and Competitive Adsorption of Cu(ⅱ), Pb(ⅱ), Ni(ⅱ) and Cd(ⅱ) onto Biochar

WANG Qi, WANG Binwei, TAN Guangcai, XU Nan†

Shenzhen Key Laboratory for Heavy Metal Pollution Control and Reutilization, School of Environment and Energy, Peking University Shenzhen Graduate School, Shenzhen 518055; † Corresponding author, E-mail: xunan@pkusz.edu.cn

Abstract Two kinds of materials including corn stalks and diary manure were used to produce the biochars (BC and DMBC) by pyrolysing at temperature of 500ºc under the protection of nitrogen atmosphere. The single and competitive adsorption characteristics of Cu2+, Pb2+, Ni2+ and Cd2+ ions onto these biochars were investigated to reveal the interaction among the metal ions on the biochar. Experimental results show that the biochars have different elemental composition. BC has a larger specific surface area, and DMBC has a bigger average pore diameter. For the single metal adsorption, the kinetics on BC are similar, but obvious differences of adsorption rates were observed on DMBC. Langmuir isotherm model well fits the sorption data of the four metal ions, and the order of sorption capacity is Pb2+>cu2+>cd2+>ni2+. Through the competitive adsorption experiments it is found that the competitive sorption capacity of Pb2+ is the strongest, and Cu2+ follows, while the sorption of Ni2+ and Cd2+ are weaker and easy to be suppressed by other divalent metal ions. Key words biochar; single adsorption; competitive adsorption; divalent metal ion

重金属污染严重威胁生态环境和人类健康。我国每年因重金属污染导致的粮食减产超过 1 千万吨, 被重金属污染的粮食多达 1200 万吨, 合计经济

损失至少 200 亿元[1]。以重金属铜为例, 它是人类所需的微量元素, 在动物和植物中含量都处在较低水平, 但在铜的开采和冶炼过程中产生大量酸性废