Arsenate removal from aqueous solution using synthetic siderite.
The study was carried out to evaluate the feasibility of synthetic siderite for As(V) removal from aqueous solution. Batch experiments were performed to investigate effects of various experimental parameters such as contact time (10 min-8 h), initial As(V) concentration (0.5-60.0 mg/L), temperature (15, 25, 35 and 45 degrees C), pH (2.0-10.0) and the presence of competing anions on As(V) adsorption on the synthetic siderite. Kinetic data reveal that the uptake rate of As(V) was rapid at the beginning and 90% adsorption was completed within 10 min at 45 degrees C and equilibrium was achieved within 3 h. The adsorption process was well described by pseudo-second-order kinetics model. The adsorption data better fitted Langmuir isotherm at low temperatures (i.e., 15 and 25 degrees C), while Freundlich isotherm at relatively high temperatures (35-45 degrees C). The maximum adsorption capacity calculated from Langmuir isotherm model was up to 31 mg/g. Thermodynamic study indicates an exothermic nature of adsorption and a spontaneous and favorable process. The optimum pH for As(V) removal was broad, ranging from 3.0 to 10.0. The As(V) adsorption was impeded by the presence of SiO(3)(2-), followed by PO(4)(3-) and NO(3)(-). The adsorption process appeared to be controlled by the chemical process. The high As uptake may attribute to both coprecipitation of As with goethite and lepidocrocite forming during the reaction and subsequent adsorption of As on these minerals.
Guo
Huaming
H
School of Water Resources and Environment, China University of Geosciences, Beijing 100083, China. hm guo@hotmail.com
Li
Yuan
Y
Zhao
Kai
K
D000327:Adsorption; D001149:Arsenates / Q000302:isolation & purification*; D002254:Carbonates / Q000737:chemistry*; D005240:Feasibility Studies; D005290:Ferric Compounds / Q000737:chemistry*; D058085:Iron Compounds; D007700:Kinetics; D008903:Minerals; D012996:Solutions; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods
D001149:Arsenates; D002254:Carbonates; D005290:Ferric Compounds; D058085:Iron Compounds; D008903:Minerals; D012996:Solutions; D014874:Water Pollutants, Chemical; C094886:goethite; C000499:ferric oxide; C486982:siderite