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A polyethylene glycol (PEG)-bentonite (BT) composite was prepared by direct polymerization of PEG in suspensions of BT. Based on detailed analyses using field-effect scanning electron microscopy, X-ray diffraction, surface area measurements and chemical methods, the obtained product was mainly composed of Ca-BT with a specific surface area of 4.13 m 2 g −1. The optimal conditions for adsorption of Pb 2+ and Cd 2+ ions were found to be a PEG content of 0.1% and a contact time of 60 min. The sorption experiments were performed under various operating variables, including polymer concentration, pH and temperature. For both Pb 2+ and Cd 2+ , the adsorption equilibrium was described by the Freundlich model, which confirmed the presence of a heterogeneous system with irregular filling of the active centres. The maximum sorption capacities of BT-PEG for removal of Pb 2+ and Cd 2+ were found to be 22 and 18 mg g −1 , respectively. The rate constants calculated for the sorption of Pb 2+ and Cd 2+ were 6.29 and 6.67 g mg −1 min −1 , respectively, at 25 • C. This study shows that the obtained sorbents based on BT may be used for treatment of waste water and could help resolve environmental protection issues.

The processes of lead and cadmium ions sorption by modified zeolite of Chankanai deposit were studied. Chitosan was used as a surface modifier due to its properties: nontoxicity, biodegradability and biocompatibility. The adsorption process was carried out at room temperature (295 K) and pH 7 under static conditions. The synthesized sorbent has been characterized by scanning electron microscopy (SEM), elemental analysis; the concentrations of Pb(II) and Cd(II) ions before and after adsorption were determined using atomic absorption spectroscopy (AAS). The Si/Al ratio of the zeolite was found to be 1.66, which showed the prospects of using this material as a source object. The static exchange capacity (SEC) of sorbents and the extraction degree of heavy metal ions were determined and compared. It was found that the removal of heavy metal ions increased with the increase of contact time (removal efficiency was 99.1±1.2% for Pb2+ and 83.4±1.2% for Cd2+). The adsorption capacity values of the modified zeolite for metal ions were (0.86±0.03) mg/g for Cd(II) and (0.68±0.03) mg/g for Pb(II). Chitosan-modified zeolite proved to be an effective adsorbent for removal of lead and cadmium ions from aqueous solutions.

A natural zeolite of Kazakh origin, as well as its three different types of chemically modified versions, were assessed from the point of view of permanganate removal yield from aqueous solutions. Modification was carried out by means of di-dodecyl-dimethyl-ammonium bromide surfactant treatment type (1). Types (2) and (3) were treated prior to DDAB wth HCl or NaCl, respectively. All sorbents display broad ranges of particle size distribution. Modification of the natural form enhances the specific surface as well as the pore volume, yet influences not in the same way the sorption yield. The process is slow, however, short-and long-term effectiveness are affected by preparation procedures. The most promising yield is exhibited by the natural zeolite that was subject to a combined acid-surfactant treatment.