Title : New sorbents based on natural mineral raw materials of Kazakhstan for after treatment of industrial wastewater from heavy metal ions
Abstract:
When purifying water from heavy metal ions, as the most dangerous component of wastewater, the practical task is to select new, cheaper and widespread materials characterized by sufficiently high mechanical strength, chemical resistance and at the same time having a more developed specific surface area and greater porosity. An essential indicator of the quality of filter materials is their resistance to acidic and alkaline environments.
Regional natural materials such as zeolite, diatomite, and vermiculite optimally combine economic profitability and efficient treatment, and are rational for extracting heavy metals from wastewater from metallurgical enterprises.
In order to establish the possibilities of using Kazakhstani mineral raw materials for wastewater treatment, the adsorption properties of zeolite, diatomite, and vermiculite rocks for a wide range of heavy metal ions have been studied.
Studies have been conducted on the extraction of heavy metals on granular filters with zeolite and diatomite loading, with a mineral content of 90-95%, fractions of 0.5-1.0 mm at a temperature of 3000C - 4000C, the flow rate of the filtered solution is 2.0 m/h. In this case, almost complete extraction of large cations of Pb2+, Fe2+, Ni2+, Mn2+, and Zn2+ is observed. At the end of the experiment, regeneration with a NaCl solution is carried out to restore the sorption capacity of the filters. After desorption, the extraction of iron, cobalt, and nickel from the solution increases by 10-30%, but the extraction of copper, zinc, and cadmium decreases by 5-30%. Sorption of heavy metals from acidic media has been investigated.
The above-mentioned sorbents and their modified forms can be used for selective or group extraction and concentration of metal ions. The kinetic patterns of the cleaning process are investigated to establish the optimal cleaning regime.
The proposed methods of sorbent modification provide the basis for studying the structure, porosity, and sorption capabilities of these natural materials. All three minerals belong to highly porous, structured materials promising for use as stable sorption systems in water treatment and water treatment.
Zeolite has a significant and similar sorption capacity not only for ions of particularly toxic (Hg2+, Cd2+, Pb2+), but also other heavy metals (Cu2+, Co2+, Ni2+, Zn2+, Ba2+, Sr2+) present in natural and wastewater in different quantities [1]. A special role is played by the significant sorption capacity of the studied clinoptilolite samples for lead ion, which makes it possible to use them for wastewater treatment and soil detoxification in the adjacent territories of metallurgical enterprises [2-4].
Diatomite, which is untreated thermally and has high adsorption rates and low permeability values, can be used as an adsorbent for fine wastewater treatment in a stationary mode. The advantage of using diatomite for fine wastewater treatment from metals is the possibility of restoring its adsorption properties after calcination at 300-4000C. Diatomite used for fine wastewater treatment from heavy metal cations can be regenerated or disposed of. Calcined diatomite, which has a relatively high permeability with a sufficiently low adsorption value, can also be used as a filtration material for coarse water purification [5]. It is possible to use diatomite in the form of granules of fractions 0,5-1,0, 0,8-2,0; 1,0-4,0, 2,5-5,0 mm.
The studied zeolite, diatomite, and vermiculite rocks (with an ion-exchange mineral content of up to 95%) are promising for use in wastewater treatment from heavy metal ions. Extraction methods are superior to sorption methods in terms of the efficiency of removing Cu2+, Zn2+, and Fe3+. Therefore, in addition to sorption extraction, a combination of sorption and extraction methods for extracting heavy metals at the post-treatment stage seems to be effective. To extract and concentrate metals, it is proposed to use sorbents of various structures and their modified forms through preliminary thermochemical treatment.
Thus, during water purification and water treatment, the possibility of using natural mineral raw materials (zeolites, diatomites, and their modified forms), whose reserves are sufficient in various regions of Kazakhstan, is shown.
