Papers by Keyword: Cadmium (Cd)

Abstract: This study compared the effectiveness of bare zero-valent iron nanoparticles (B-nZVI) and starch-stabilized zero-valent iron nanoparticles (S-nZVI) in immobilizing Pb and Cd from lead-acid battery waste soils. Both B-nZVI and S-nZVI were prepared in almost identical manner using the technique of reducing ferric chloride with sodium borohydride. X-ray diffraction (XRD) and dynamic light scattering (DLS) analyses confirmed that polydisperse B-nZVI and S-nZVI were synthesized. XRD and DLS analyses showed that B-nZVI and S-nZVI had different surface properties. To assess the immobilization capability of B-nZVI and S-nZVI, a composite soil sample was collected from an automobile lead-acid battery waste dumpsite. The soil sample had a pH of 3.85 and Pb and Cd levels of 16,674 mg/kg and 41 mg/kg, respectively. Single extraction procedures using 0.01M CaCl₂, 0.1 M HCl, and 0.05 M EDTA were used to simulate phytoavailable Pb and Cd in the soil studied. Batch immobilization analysis showed that Cd was mobile in the control but immobile in B-nZVI and S-nZVI treated soils. Pb was however not immobile in either the control or treated soils. The mobility of Pb however decreased with increasing doses of S-nZVI and 0.003 g of S-nZVI was needed to make Pb completely immobile in soil. Batch immobilization also showed that S-nZVI was 1.8-2.49 times more efficient in immobilizing Pb than B-nZVI. Simulated phytoavailability of Pb was in the order of EDTA > HCl > CaCl₂ > H₂O while simulated photoavailable Cd was in the order of HCl > EDTA > H₂O > CaCl₂.

Abstract: Cadmium Selenide (CdSe) was obtained by using spray-deposited method which is using the sodium selenosulfite as Se precursor and cadmium chloride (CdCI) as cadmium (Cd) precursor. Time for each spray-deposited was used as the main parameter to investigate the properties of CdSe nanoparticles. By using FESEM for surface morphology and X-ray Diffraction (XRD) studies reveal that the CdSe nanoparticles with cubic crystal structures. In this research, the effect of time of spray deposited was main parameter to know the CdSe properties. The set of time was set from 10 min until 50 min. From FESEM result the size of CdSe nanoparticles were in the range 60-70 nm and the crystalline was hexagonal from XRD result. By using Scherrer equation, the size of crystalline of CdSe nanoparticles was determined from XRD characterization, the size was 60-70 nm. The size of CdSe nanoparticles from FESEM images were 60-80nm.

Abstract: The use of low-cost adsorbent derived from agricultural waste has been investigated for the removal of Cd (II) from aqueous solution. This research reports the feasibility of using solid pineapple waste (SPW), sugarcane bagasse (SCB) and activated carbon (AC) derived from palm kernel for the removal of Cd (II) under different experimental conditions. Batch experiments were carried out at various pH (3-12), adsorbent dosage (0.01-2 g) and contact time (15-150 min). The maximum Cd (II) removal was shown by SPW (90%) followed by SCB (55%) and AC (30%) at pH 7 with a contact time of 120 min, adsorbent dosage of 1.0 g and at 1.0 ppm of the initial concentration of Cd (II) solution. The kinetics study shows that the adsorption process fitted the pseudo-second-order-model. The experimental data was analysed by both Freundlich and Langmuir isotherm models. It was found that the Langmuir model appears to well fit the isotherm. The Langmuir maximum adsorption capacity calculated from Langmuir for SPW, SBC and AC were 0.3332 mg/g, 0.1865 mg/g and 0.1576 mg/g respectively. The order of Cd (II) removal by the adsorbents was SPW>SCB>AC. Thus, SPW may be an alternative adsorbent for the removal of Cd (II) ions form aqueous solution. The characterization of the SPW, SCB and AC were also carried out by using Scanning Electron Microscopy (SEM) and Nitrogen Gas Adsorption Single Point Surface Area Analyzer (BET).

Abstract: The growth, photosynthetic gas exchange and chlorophyll fluorescence were investigated in wild type and mutant rice plants treated with 50 μmol L^-1 Cd. The results showed that plant height, dry mass, and chlorophyll content decreased by Cd treatment, and the mutant showed more severe reduction than wild type rice. Net photosynthetic rate (Pn), transpiration rate (E), stomatal conductance (Gs), maximal photochemical efficiency of PSII (Fv/Fm), effective PSII quantum yield (ΦPS2), and photochemical quenching (qP) were decreased and intercellular CO₂ concentration (Ci) and and non-photochemical quenching (qN) were enhanced in Cd-treated plants with the increasing of Cd exposure time, with changes in the mutant being more evident. The results suggest that Cd inhibits photosynthesis due to non-stomatal limitations and the response of PSII reaction centre and the mutant has less capacity of acclimation to Cd stress.

Abstract: In order to estimate the present exposure risk of Cadmium dietary intake by inhabitants in a W-Mo mining area, South China, a dietary investigation was conducted with stratified cluster random sampling method. According to the result, a total of 7 food groups, including rice, vegetable, meat, chicken and egg, were sampled from contaminated areas using the total dietary study method. Rice consumption took up 81.5% of food consumption. Cadmium content in 45.8% of 306 rice samples, 11.1% of 252 vegetable samples, and 4.8% of 21 chicken samples exceeded the limit. Risks of cadmium in study area are between 1.0E-06 and 1.0E-03, which is acceptable but need further attention to reduce them. Rice products were the highest contribution, which took up about 80.1%. The results showed that Cadmium intake was much higher around W-Mo ore deposit than that in reference area.

Abstract: This study was conducted using the data collected at the Anping Harbor, Taiwan to investigate and analyze cadmium (Cd) contained in the sediments, and to evaluate the accumulation of Cr and the degree of its potential risk. The results show that samples collected at ten monitoring points contain 0.040.60 mg/kg of Cd with an average of 0.26±0.18 mg/kg. The spatial distribution of Cd reveals that the Cd concentration is relatively high in river mouth region, and gradually diminishes toward the harbor region. This indicates that upstream industrial and municipal wastewater discharges along the river bank are major sources of pollution. Results from the enrichment factor and geo-accumulation index analyses imply that the Bamboo River mouth sediments can be characterized as moderately severe enrichment and moderate accumulation of Cd, respectively. Results of potential ecological risk index indicate that the surface sediment has higher ecological potential risk in Bamboo River mouth. The results can provide valuable information to developing future strategies for the management of river mouth and harbor.

Abstract: The montmorillonite supported nanozero-valent iron material (MT-NZVI) was synthesized to remove cadmium (Cd). The results showed that the removal efficiency of MT-NZVI on cadmium was much higher than that of montmorillonite (MT), and the removal efficiency of MT-NZVI on cadmium reduced with the increase of the initial concentration and the pH value, but increased with the increase of the dosage.

Abstract: A new Cd (II) ion-imprinted polymer (Cd (II)-IIP), which can be used for selective adsorption of Cd (II) from aqueous solutions, was successfully prepared based on silica gel particles with the help of surface molecular imprinting technology. The adsorption kinetic curve, adsorption isotherm and selective adsorption were measured by static method. The adsorption kinetics of IIPs for Cd (II) reached the equilibrium at about 10 min. The maximum adsorption capacity was 29.36 mg/g, and the IIPs had much higher adsorption quantity than NIPs. Competitive adsorption studies showed that Cd (II)-IIP offers the advantages of selectivity toward targeted Cd (II) compared with NIP in the presence other metal ions. The results showed that the IIPs possessed good specific adsorption capacity and selectivity for Cd (II).

Abstract: Peanut shell Cellulose Xanthate (PCX) was prepared by reacting with carbon disulphide after mercerized by sodium hydroxide solution. The preparing conditions (hydroxide solution concentration, carbon disulphide dosage, temperature) were optimized in this study. And the effects of PCX amount and contact time on the removal of Cd (II) ion from aqueous solution was studied,the results indicated that when the initial Cd (II) ion concentration was 10mg/L, the adsorption capacity of PXC was high effective with the PCX amount was 1g/L and the contact time was 1.5h,the equilibrium adsorption capacity of PCX was 9.87 mg/g and the removal rate of Cd (II) ion was 98.72%.Then the regeneration capacities of PCX adsorbent was investigated, the results indicated that the removal rate of Cd (II) ion was more than 75% after regeneration. All the results indicated that the PCX can be used as a low cost but effective biosorbent for heavy metals remediation.

Abstract: A pot trial with a soil-sand combination culture in rhizosphere bags was conducted to study the effects of applying Se in soil on formation of iron plaque outside roots, rice growth and absorption of Se and Cd under the control conditions. The results showed that application of low concentration Se (1.0 mg/kg) can promote the formation of iron plaque outside roots, but application of high concentration Se (8.0 mg/kg) can inhibit formation of iron plaque outside roots. Whether applying Cd or not, Se on rice growth had no significant effect, which explained Se on rice growth had not produced toxic effects. With the increasing of Se treatment concentrations, the Cd content of roots, stems, leaves, rice husks and rice significantly decreased. Application of selenium can improve the selenium content in rice, which explained rice had enrichment effect for selenium.