Lead and Cadmium Adsorption onto Iron Oxides and Manganese Oxides in the Natural Surface Coatings Collected on Natural Substances in the Songhua River of China

Natural surface coatings collected from natural substances （NSCsNS） were employed to study the roles of the main chemical components （iron oxides, manganese oxides, and other components） in controlling the adsorption of lead（Pb） and cadmium（Cd） in aquatic environments. The selective chemical extraction followed by the adsorption of Pb and Cd experiments and statistical analysis, were used to investigate the adsorption property of each component. Hydroxylamine hydrochloride was used to remove manganese oxides selectively, and sodium dithionite was used to extract iron oxides and manganese oxides. The result indicated that iron oxides and manganese oxides played an important role in the adsorption of Pb and Cd on NSCsNS, and the relative contribution was about two-thirds. The contribution of manganese oxides was the greatest, with a lesser role indicated for other components. The adsorption ability of manganese oxides for Pb and Cd was greater than that of iron oxides or other components for Pb and Cd. The Pb adsorption observed in each component was greater than Cd adsorption.

Adsorption of Cadmium by Soil Colloids and Minerals in Presence of Rhizobia

Experiments were conducted to study the adsorption of Cd on two soil colloids (red soil and yellow- brown soil) and three variable-charge minerals (goethite, noncrystalline Fe oxide and kaolin) in the absence and presence of rhizobia. The tested strain Rhizobium fredii C6, tolerant to 0.8 mmol L-1 Cd, was selected from 30 rhizobial strains. Results showed that the isotherms for the adsorption of Cd by examined soil colloids and minerals in the presence of rhizobia could be described by Langmuir equation. Within the range of the numbers of rhizobial cells studied, the amount of Cd adsorbed by each system increased with increasing rhizobial cells. Greater increases for the adsorption of Cd were found in red soil and kaolin systems. Rhizobia influence on the adsorption of Cd by examined soil colloids and minerals was different from that on the adsorption of Cu. The presence of rhizobia increased the adsorption sanity of soil colloids and minerals for Cd, particularly for the goethite and kaolin systems. The discrepancies in the influence of rhizobia on the adsorbability and affinity of selected soil colloids and minerals for Cd suggested the different interactions of rhizobia with various soil components. It is assumed that bacterial biomass plays an important role in controlling the mobility and bioavailability of Cd in soils with kaolinite and goethite as the major colloidal components, such as in variable-charge soil.

Succinate-bonded pullulan: An efficient and reusable super-sorbent for cadmium-uptake from spiked high-hardness groundwater

Chemically modified pullulan was evaluated for its sorption efficiency and selectivity to remove cadmium（Cd） from spiked high-hardness groundwater（GW）. Pullulan esterified with succinic anhydride using dimethylaminopyridine showed a fairly high degree of substitution value as confirmed by1 H NMR spectroscopy. Pullulan succinate（Pull-Suc） was converted into the sodium salt（Pull-Suc-Na）. The effect of contact time（5–200 min） and p H（2–8） on Cd-uptake by the sorbent（Pull-Suc-Na） was investigated. The sorbent showed more than 90% Cd-removal in first 15 min from distilled water（DW） and GW solution,respectively. Comparison of Pull-Suc-Na with other polysaccharidal sorbents suggested its high efficiency（DW 476.2 mg/g and GW 454.5 mg/g） and selectivity for the removal of Cd by an ion exchange mechanism, which is further supported by the negative Gibbs free energy values calculated from Langmuir isotherms. A Langmuir isotherm kinetic model provided the best fit for the sorption of Cd using Pull-Suc-Na. The sorbent showed a negligible decrease in Cd-uptake over three regeneration cycles. The thermal stability testing of the sorbents indicated that Pull-Suc-Na（sorbent） is more stable than Pull-Suc.

Cd(Ⅱ)removal from phenols-bearing wastewater using magnetic carbon nanotubes

This project studied Cd(Ⅱ)uptake from phenols-bearing wastewater using magnetic carbon nanotubes(MCNT)as adsorbent.Initially,Cd(Ⅱ)complexation with various phenols was confirmed by FT-IR spectroscopy.Factors affecting Cd removal are:solution pH;type of phenol[phenol(Ph),2-chlorophenol(2-CP),2-nitrophenol(2-NP),and 2,4-dinitrophenol(2,4-DNP)];Mag:CNT mass ratio;Cd:phenolic compound molar ratio;and the effect of order of adding adsorption components(MCNT,Cd(Ⅱ),phenolic compound)to the extraction medium.It was found that the presence of phenols in the extraction medium caused a 10e50%decrease in Cd(Ⅱ)uptake.This was probably due to a competition between phenols/surface functional groups towards Cd(Ⅱ);or phenols/Cd(Ⅱ)to occupy the surface functional groups.2,4-DNP was selected as a model phenolic compound.The optimum adsorption conditions[1:1 M ratio of(Cd(Ⅱ):2,4-DNP)at pH 6 using MCNT(1:1)adsorbent]resulted in adsorption capacity of 17.9 mg Cd g^(-1).The best order of adding reagents was(Cd(Ⅱ)þMCNT(1:1))and then 2,4-DNP.The regeneration of the adsorbent was possible by using 0.5 M HNO_(3)where 90%of adsorption efficiency was reserved after three times of successive use.Upon presence of co-existing ions,75%of the adsorption efficiency was maintained.The applicability of the proposed adsorption method on real water samples was evaluated.