Cadmium ion adsorption by amine-modified activated carbon

Cadmium Depth Separation Method in Polymetallic Sulfate Solution: Flow-Electric Field Enhanced Cementation Combined with M5640 Extraction

An efficient and controllable process for separating copper and cadmium was required to be developed due to the high cost of the long separation process of copper cadmium slag generated from the zinc smelting process. Therefore, a new process for the application and deep separation of copper and cadmium was developed by combining the Circulating Flow Electric (CFE) cadmium cement method and the 2-hydroxy-5-nonyl formaldehyde oxime (M5640) copper extract method. The process firstly removed copper ions utilizing M5640 and obtained a primary purification solution, followed by CFE method to extract cadmium in depth. The effects of extractant volume fraction, pH, Oil phase/Aqueous phase (O/A) ratio and reaction time on the removal of copper ions were investigated. The results showed that the removal of copper was above 97%, while the removal of zinc and cadmium was below 1.6%, respectively, proved that the selectivity of M5640 for copper was significantly higher than that for metals such as cadmium and zinc. The characterization results indicate that the oxygen on the hydroxyl group and the nitrogen on the oxime group co-ligated with the copper ions and subsequently formed chelated extracts. That was the mechanism of the copper ion purification by M5640. Furthermore, the extraction of high purity cadmium was carried out in the extraction residual liquid. A novel method of cadmium removal enhanced by coupling an electric field with a circulating flow field was developed and applied to the cement cadmium from sulfate solutions. The optimal process conditions of the method were explored, which were further fitted into statistical equations and optimized by response surface analysis. Since the fitted theoretical results were close to the experimental results, the optimization was considered as effective. The optimized experimental parameters were 6.23 mL/s of flow rate, 48.14 mA/cm2 of current density, 2.25 of pH, and 0.93 of anode/cathode area ratio, respectively. Next, the extraction electrical efficiency, purity and its weight distribution in the cell of cadmium sponge under different flow fields were calculated and measured. The results were analyzed to prove the existence of an optimal interval for the distribution of cadmium under high-speed flow field.

Highly efficient Cd(II) adsorption using mercapto-modified bentonite as a novel adsorbent: an experimental design application based on response surface methodology for optimization

We report the optimization with response surface methodology (RSM) for adsorption conditions required for removal of Cd(II) from an aqueous environment with 3-mercaptopropyl trimethoxysilane-modified bentonite (MMB). Central composite design (CCD) in RSM was used to optimize the most significant adsorption variables of initial pH, temperature (°C), initial Cd(II) concentration (C_o, mg L^-1) and adsorbent dosage (g). With the quadratic model equation obtained from CCD, the optimum values were determined as initial pH 6.40, temperature 20 °C, C_o 49.55 mg L^-1 and adsorbent dosage 0.17 g. Under optimum conditions, the optimum adsorption amount of Cd(II) was 27.55 mg Cd(II)/g adsorbent and adsorption yield was 94.52%. The obtained results showed that the Langmuir and Dubinin Radushkevich (D-R) adsorption isotherms were more suitable for adsorption equilibrium data. The kinetic studies indicated that the pseudo-second-order kinetic model was fitted to the adsorption kinetic data. Additionally, thermodynamic studies indicated that the adsorption process was spontaneous and exothermic. As a result, MMB can be chosen as an effective adsorbent for treating heavy metals such as Cd(II) in wastewater and removing them from aqueous solutions. Furthermore, it is thought that it will positively contribute to the literature since the adsorbent-adsorbate combination (MMB-Cd(II)) is used for the first time.