Removal of Ca2+ and Zn2+ from aqueous solutions by zeolites NaP and KP

Evaluation of groundwater hardness removal using activated clinoptilolite

Current study aimed to investigate modified natural clinoptilolite for removal of calcium and magnesium from the groundwater. Feasibility of clinoptilolite for groundwater hardness removal in production and operation was verified by static adsorption experiment and the experiment of fixed bed and degasification column. Subsequently, the main parameters for groundwater treatment using clinoptilolite were also explored. Results show that in the process of clinoptilolite in adsorption is dominant reaction process. The adsorption equilibrium time was unchanged when the hardness of raw water changes from 450 to 550 mg/L. With respect to comparative analysis of price and performance, NaCl found to be the most suitable clinoptilolite regenerated agent. The adsorption efficiency was high when the residence time was 20-25 min in the pilot experiments. The reaction mechanism was mainly substitution reaction according to ion equilibrium, and the treatment capacity of the degasifier combined with the fixed bed was 20% higher than that of with only fixed bed.

Sericite in the remediation of Cd(II)- and Mn(II)-contaminated waters: batch and column studies

Sericite, a mica-based natural clay was employed in the remediation of waters contaminated with two important heavy metal toxic ions, viz. Cd(II) and Mn(II), under batch and column experimentation. The batch reactor studies were intended to study various physicochemical parameters, viz. effect of sorptive pH, concentration, contact time, and background electrolyte concentrations which helped to deduce the mechanism involved at the solid/solution interface. The percent uptake of Cd(II) and Mn(II) was increased with increasing of the sorptive pH, and almost 100 % of these cations were removed at pH 10. Equilibrium-state sorption data was modeled and fitted well to the Langmuir and Freundlich adsorption isotherms. The kinetic data followed the pseudo-first-order and pseudo-second-order kinetic models. Increasing the background electrolyte concentrations by 100 times caused significant decrease of the uptake of Cd(II) and Mn(II) ions, which inferred that these metal cations were less adsorbed specifically and predominantly attached with relatively weak electrostatic attraction onto the solid surface. Additionally, the fixed-bed column reactor operations were also performed to assess the suitability of sericite in the attenuation of Cd(II) and Mn(II) from aqueous solutions under dynamic conditions. The breakthrough data obtained were successfully utilized to fit into a nonlinear fitting of Thomas equation. The results showed that the naturally and abundantly available sericite could be a potential natural material in the remediation of aquatic environment contaminated with Cd(II) and Mn(II).

Response surface methodology for the modelling of 85Sr adsorption on zeolite 3A and pumice

The adsorption of 85Sr from aqueous solutions on to zeolite 3A and three types of pumice materials (i.e. Kayseri, Isparta and Nevsehir) was investigated in this study. Experiments with radioactive 85Sr were performed to test the sorption ability of the sorbents to remove this radioisotope from liquid radioactive wastes. The influence of sorbent dosage and initial activity of feed solution on the decontamination factor were analysed and optimized by means of response surface methodology. The parameters of the experiments, namely temperature, pH, time, stirring efficiency, were selected in preliminary tests. The experimental results showed that the most efficient pumice sorbent for 85Sr is Isparta, for which a maximal decontamination factor of 76.92 was obtained by using the sorbent dosage of 0.5% w/v. However, the commercial zeolite 3A was 2.71-fold more efficient than Isparta pumice for decontamination of strontium radioactive solutions. Isparta pumice is a low-cost natural sorbent, and its ability to effectively bind strontium radioisotope from water solutions suggests that this material has further applications for radioactive waste treatment.

The effect of the presence of metatartaric acid on removal effectiveness of heavy metal ions on chelating ion exchangers

The paper presents experimental results and their evaluation for the sorption of copper(II), zinc(II), cobalt(II) and nickel(II) complexes with metatartaric acid on chelating ion exchangers with different functional groups. The literature lacks the data concerning sorption of heavy metal ions in the presence of metatartaric acid on ion exchangers. The effect of important parameters such as the value of pH, the metal(II) ion and ligand concentration as well as their molar ratio and the type of functional group of the ion exchanger used was studied. It was found that the time of 60 min was sufficient for sorption to attain equilibrium. The equilibrium sorption capacities for copper(II), zinc(II), cobalt(II) and nickel(II) complexes with metatartaric acid were 37.35 mg/g, 32.02 mg/g, 32.78 mg/g and 28.31 mg/g on Lewatit TP 207 and 42.15 mg/g, 34.32 mg/g, 27.76 mg/g and 21.70 mg/g on Lewatit TP 260, respectively. The sorption optimum pH was 7. Temperature does not affect the sorption process significantly. The sorption data were well fitted by the Langmuir adsorption model whereas kinetics of the sorption process was well described by the pseudo second order kinetics equation.