Adsorption of copper and lead from rainwater using adsorbents based on diatomite and calcium alginate

Contamination of water bodies with toxic heavy metals poses significant problems in many countries. Copper and lead are harmful toxic metals found in rainwater. Readily available, economical, and envi-ronmentally friendly sorption materials are sought to remove these metals, and this study focuses on their removal. Capsules of calcium alginate combined with diatomaceous earth were prepared by mix-ing sodium alginate with diatomite, which was added to a calcium chloride solution. Alginate forms hydrogels in the presence of divalent cations. These materials were characterized by scanning electron microscopy, point analysis energy-dispersive X-ray spectroscopy, and measuring the surface area and pore size distribution using the Brunauer–Emmett–Teller (BET) low-temperature nitrogen adsorption and desorption technique (BET). Additional studies examined adsorption under static conditions to determine the adsorption isotherms and adsorption kinetics of copper and lead and showed high levels of both copper and lead removal. Efficiencies of 91.2% and 91.6% at a dose of 2 g/L for 2 h were achieved for copper and lead removal, respectively. The best rainwater solution results were obtained for copper at pH 6 and pH 8 for lead. Therefore, encapsulation of diatomite with alginate polymer is a solution to adsorption problems during the recovery of fine particles of diatomite from aqueous solutions.