Optimization of Process Parameters and Kinetics Analysis of Cd Removal in ZnSO4 Production

In order to optimize the process parameters of Cd removal in the ZnSO4 production process and study the mechanism of Cd removal reaction, the response surface methodology was used to arrange Cd removal experiments and analyze the optimal production conditions, and the mechanism of Cd removal was studied using kinetics. The results show that the optimal process conditions for Cd removal are as follows: reaction temperature 55 °C, reaction time 13.43 min, and the zinc powder dosage should be 2.14 times that of Cd; the main effects of the three variables from large to small are zinc powder dosage, reaction temperature and reaction time; Cd removal is a second-order reaction, and the activation energy of the reaction is 29.6986 kJ/mol, so the reaction conforms to the diffusion control mechanism.

Enhanced Electrokinetic Remediation of Cadmium (Cd)-Contaminated Soil With Interval Power breaking

This study compared electrokinetic (EK) remediation with and without interval power breaking in the removal of total and plant available cadmium (Cd) in the soil. Two laboratory experiments, i.e. EK remediation with interval power breaking (24-12 h power-on-off cycles) and conventional EK remediation (continuous power supply) with the same accumulated time (192 h) of power supply were conducted to remove soil Cd. After the EK remediation by interval power breaking, the total Cd removal efficiency in the soil rose to 38%, in comparison to 28% by the conventional EK remediation. As for the plant available Cd, the removal efficiency was enhanced from 52% to 63%. Additionally, the electric current during the EK remediation and electric conductivity after the EK remediation were higher in the soil treated by interval power breaking, which indicated an enhanced desorption and/or migration of charged species. It further meant that the higher removal efficiency of soil Cd by interval power breaking could be related to the enhanced desorption and/or migration of Cd species. This study indicated that both conventional EK remediation and EK remediation with interval power breaking were effective methods to remove soil Cd but EK remediation with interval power breaking was more efficient.

Functionalization and Evaluation of Inorganic Adsorbents for the Removal of Cadmium in Wastewater

This study presents the feasibility of using various functionalized substrates, Fe3O4 nanoparticles (NPs) and Al2O3 spheres, for the removal of Cd from aqueous solution. To improve the materials’ affinity to Cd, we explored four different surface modifications, namely (3-Aminopropyl) triethoxysilane (APTES), L-Cysteine (Cys) and 3-(triethoxysilyl) propylsuccinic anhydride (CAS). Particles were characterized by FTIR, FIB-SEM and DLS and studied for their ability to remove metal ions. Modified NPs with APTES proved to be effective for Cd removal with efficiencies of up to 94%, and retention ratios up to 0.49 mg of Cd per g of NPs. Batch adsorption experiments investigated the influence of pH, contact time, and adsorbent dose on Cd adsorption. Additionally, the recyclability of the adsorbent and its potential phytotoxicity and animal toxicity effects were explored. The Langmuir, Freundlich, pseudo-first-order and pseudo-second-order models were applied to describe the behavior of the Cd adsorption processes. The adsorption and desorption results showed that Fe3O4 NPs modified with APTES are promising low-cost platforms with low phytotoxicity for highly efficient heavy metal removal in wastewater.

Pengolahan Tanah Tercemar Logam Berat Pb dan Cd Menggunakan Biochar Sekam Padi dengan Variasi Ukuran Partikel

Soil contamination by heavy metals lead (Pb) and cadmium (Cd) is a form of pollution that is very dangerous for living things. One of the efforts to cultivate polluted soil is the remediation method using biochar from rice husks. The purpose of this study was to analyze the effect of biochar particle size variations on the removal of heavy metals Pb and Cd on contaminated soil. Biochar is made by pyrolysis at 500 0C for 1 hour and flows 0.1 L / minute of N2 gas. This study used a variety of biochar particle sizes of 100 mesh, 60 mesh, 40 mesh and testing time every 10 days for 1 month. The results of this study were the highest Pb and Cd removal in the addition of biochar with a particle size of 100 mesh, namely with a Pb concentration of 91.32 mg / kg and a removal efficiency of 54.05% ; Cd concentration of 10.47 mg / kg and a removal efficiency of 47.36%. Based on the results obtained, it can be stated that the smaller the biochar particle size, the efficiency of heavy metal removal will increase.

Remediation of Cd-Contaminated Soil by Modified Nanoscale Zero-Valent Iron: Role of Plant Root Exudates and Inner Mechanisms

In this study, the role of exogenous root exudates and microorganisms was investigated in the application of modified nanoscale zero-valent iron (nZVI) for the remediation of cadmium (Cd)-contaminated soil. In this experiment, citric acid (CA) was used to simulate root exudates, which were then added to water and soil to simulate the pore water and rhizosphere environment. In detail, the experiment in water demonstrated that low concentration of CA facilitated Cd removal by nZVI, while the high concentration achieved the opposite. Among them, CA can promote the adsorption of Cd not only by direct complexation with heavy metal ions, but also by indirect effect to promote the production of iron hydroxyl oxides which has excellent heavy metal adsorption properties. Additionally, the H+ dissociated from CA posed a great influence on Cd removal. The situation in soil was similar to that in water, where low concentrations of CA contributed to the immobilization of Cd by nZVI, while high concentrations promoted the desorption of Cd and the generation of CA–Cd complexes which facilitated the uptake of Cd by plants. As the reaction progressed, the soil pH and cation exchange capacity (CEC) increased, while organic matter (OM) decreased. Meanwhile, the soil microbial community structure and diversity were investigated by high-throughput sequencing after incubation with CA and nZVI. It was found that a high concentration of CA was not conducive to the growth of microorganisms, while CMC had the effect of alleviating the biological toxicity of nZVI.