Removal of heavy ions contamination, especially chromium, from polluted water sources using bentonite adsorbent

Contamination of toxic heavy metal in wastewater from industrial effluent is one of the most significant factors causing the environmental issues worldwide. The presence of heavy metal in the environment, particularly in an aquatic environment, leads to the organism mortality due to its high toxicity and its capability to be accumulated in a living organism and dispersed through the food chain system. Chromium is one of the most widely utilized heavy metals in human livelihood. It has been utilized in various industries, i.e., manufacture, tanning, leather, photography, glass, craft, and electroplating due to its unique characteristic. In other hands, chromium is also one of the most notorious heavy metals[۱]. The maximum allowable discharge of Cr in aquatic environments is ۰.۰۵ mg/ dm۳, whereas the total Cr should be less than ۲.۰ mg/dm۳. researchers have used several methods, such as ion exchange, ultrafiltration, reverse osmosis, electrodialysis, chemical precipitation, evaporation, solvent extraction, membrane processes coagulation, flocculation, biological treatment and chemical oxidation to remove or reduce Cr (VI)[۲]. the adsorption process directly depends on the type of adsorbent and its properties. the adsorbents should be cheap, environmentally friendly, and efficient. Several adsorbents such as activated carbon, zeolite, chitosan, hydrogel, and clays have been studied to remediate toxic heavy metals from soil and wastewater. clays and clay minerals utilization as an adsorbent gained high concern due to its high surface area and high ion exchange capability. Bentonite is one of the most studied clays over the other clays such as kaolin, ball clay, laponite. Bentonite is mainly composed of ۸۵% montmorillonite minerals[۱,۲]. It is acceptable. In a research study, the effect of pH parameters, time and amount of adsorbent has been investigated,and the optimal adsorbent condition for the removal of hexavalent chromium is ۰.۵ ppm , The amount of adsorbent ۲ g/L, It reaches its equilibrium time in ۶۰ minutes, The pH level in aqueous solutions has a very strong effect on the absorption of adsorbents in such a way that the efficiency of the adsorbent is very high in acidic conditions, but due to the lack of conditions in the storage of acidic aqueous solutions, neutral conditions can also provide optimal efficiency for the adsorbents.

کلیدواژه ها:

Adsorption ، Hexavalent chromium ، Bentonite ، Clay