title: Effects of organic acids on adsorption of lead onto montmorillonite, goethite and humic acid.
abstract: Adsorption isotherms for Pb onto six soil components (quartz, feldspar, kaolinite, montmorillonite, goethite and humic acid) were studied. The influence of pH, EDTA and citric acid on the adsorption of Pb onto montmorillonite, goethite and humic acid were considered. Results indicate that the experimental data fit the Langmuir Adsorption Isotherm. The adsorption capacity for Pb at pH 6 was found to be in the order: humic acid (22.7 mg g(-1)) > goethite (11.04 mg g(-1)) > montmorillonite (10.4 mg g(-1)) > kaolinite (0.91 mg g(-1)) > feldspar (0.503 mg g(-1)) > quartz (0.148 mg g(-1)). Generally, the amount of Pb adsorbed onto montmorillonite, goethite and humic acid decreased with increasing concentrations of EDTA and citric acid and with increases in alkality. However, there were two exceptions: (1) addition of citric acid increased the amount of Pb adsorbed onto humic acid; and (2) the amount of Pb adsorbed onto goethite decreased with increasing pH in the presence of EDTA. Some mechanisms involved in the adsorption reactions are discussed.
authors.affiliation: State Key Laboratory of Pollution Control and Resources Reuse, Department of Environmental Sciences and Engineering, Nanjing University, Nanjing 210093, PR China.
authors.forename: Zhenghua
authors.initials: Z
authors.lastname: Wu
authors.forename: Zhimang
authors.initials: Z
authors.lastname: Gu
authors.forename: Xiaorong
authors.initials: X
authors.lastname: Wang
authors.forename: Les
authors.initials: L
authors.lastname: Evans
authors.forename: Hongyan
authors.initials: H
authors.lastname: Guo
mesh_terms: D000327:Adsorption; D019343:Citric Acid / Q000494:pharmacology*; D004492:Edetic Acid / Q000494:pharmacology*; D019015:Geologic Sediments; D006812:Humic Substances / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007854:Lead; D012989:Soil Pollutants
chemical_list: D006812:Humic Substances; D012989:Soil Pollutants; D019343:Citric Acid; D007854:Lead; D004492:Edetic Acid