Screening a new biosorbent with low cost and high efficiency from a native plant material is a key to the adsorption of heavy metal ions from wastewater. In this study, the potential of Phytolacca americana L. as a biosorbent for Pb(II) removal from aqueous solutions was investigated. Experiments were performed to evaluate the effect of biosorbent dosage, pH, initial Pb(II) concentration and contact time on the Pb(II) removal. The results indicated that the hydroxyl, carboxyl and amine groups may take part in Pb(II) binding. HNO 3 -modified P. americana (HPAL) showed a significant higher uptake capacity compared to original P. americana (PAL) (p < 0.05). A dose of 20 g L À1 of biosorbents in solutions with an initial pH of 6.0, an initial Pb(II) concentration of 30 mg L À1 and a contact time of 120 min resulted in the maximum Pb(II) removal efficiency. The Freundlich isotherm gave a better fit than the Langmuir isotherm revealed that the biosorption was potentially multilayer. Further, the adsorption kinetics followed a pseudo second-order model, which implied that the biosorption was mainly a chemisorption process. The thermodynamic properties showed that the Pb(II) adsorption onto the P. americana biomass was feasible, spontaneous and exothermic in nature. Both physisorption and chemisorption were involved in the biosorption of Pb(II) onto the surface of P. americana biomass through electrostatic interaction and ion exchange. Additionally, desorption studies revealed promising regeneration potential of these biosorbents. The present study showed that P. americana biomass could be used
Anthropogenic activities could result in increasing concentrations of heavy metals in soil and deteriorating in soil environmental quality. Topsoil samples from a typical industrial area, Shiting River Valley, Sichuan, Southwest China, were collected and determined for the concentrations of Cu, Zn, Cr, Cd, As, and Hg. The mean concentrations of these metals were lower than the national threshold values, but were slightly higher than their corresponding background values, indicating enrichment of these metals in soils in the valley, especially for Cu, Zn, and Hg. The topsoils in this area demonstrated moderate pollution and low potential ecological risk. Principal component analysis coupled with cluster analysis was applied to analyze the data and identified possible sources of these heavy metals; the results showed that soil Cd, Hg, As, Cu, and Zn were predominantly controlled by human activities, whereas Cr was mainly from the parent material. The spatial distribution of the heavy metals varied distinctly and was closely correlated to local anthropogenic activities. Furthermore, the concentrations of heavy metals in the industrial land demonstrated relatively higher levels than those of other land use patterns. Soil metal concentrations decreased with the distance increase from the traffic highway (0-1.0 km) and water system (0-2.0 km). Additionally, soil properties, especially pH and soil organic matter, were found to be important factors in the distribution and composition of metals.
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