Preparation and evaluation of altered zeolite and diatomite as affordable adsorbents in contaminated water treatment

Natural diatomite as well as zeolite has been recognized as useful affordable adsorbents for water treatments for heavy metals elimination. The raw materials, zeolite and diatomite were modified using organic acid (citric acid) in different molarity degrees, i.e., 0.2, 0.4, 0.6, 0.8 and 1.0 molar, aiming to increase their surface area by forming new functional groups and increasing the active sites. The modifiers were tested as adsorbent materials for eliminating heavy metals (Fe, Zn, Cr, Pb, Cu, Al, Ni, As and Cd) from El-Batts drain wastewater, Fayoum, Egypt. Also, diatomite as well as zeolite were investigated regarding surface chemistry (SEM), (FTIR), and antimicrobial activities. Batch adsorption trials were performed, and four kinetic models employed in assessing heavy metals release's data compliance from studied contaminated water including Elovich, Parabolic diffusion, modified Freundlich, and first-order equations. Results revealed that metals adsorption on zeolite and diatomite conforms well to Elovich model. The kinetic studies were better fitted to the Elovich and modified Freundlich models. With a correlation coefficient (R² > 0.98), heavy metals elimination by the various treatments was significantly correlated with the Elovich, first-order and modified Freundlich models. Results showed the treated zeolite and diatomite materials were verified to be functional adsorbents for minimizing the hazards of heavy metals from low-quality water to the permissible levels. In addition, washing, heating, and treating zeolite and diatomite with moderate organic acid (citric acid) could increase the active sites and boost their surfaces with open pores and channels. The treatment of zeolite and diatomite with citric acid at 0.6 and 0.2 M, respectively, exhibited optimal molarity values to increase their adsorption capacity to the studied inorganic pollutants with their various concentrations.