Detoxification of heavy metals from Oryza Sativa rice by novel agro waste: Rice husk treated by coffee bean

Abstract

Rice is one of the most widely consumed grain crops (besides wheat and maize) in Iran and various countries. Currently, more and more rice is found to be contaminated with heavy metals, which can have a negative impact on human health. The current study aimed to investigate the impact of coffee bean waste (CBW) and Rice Husk ( RH) as bio-adsorbent in reducing Lead, Arsenic, Cadmium, and Nickel in rice (Oryza Sativa). 950 rice samples were collected from various markets in Tehran to extract the heavy metal content in raw, rinsed, soaked with adsorbent, and cooked and drained rice, determined and measured by wet digestion method. Final concentrations of heavy metals in rice samples were analyzed using Inductively Coupled Plasma Optical Emission Spectroscopy according to AOAC International Standards. Batch adsorption experiments were carried out to evaluate the effect of adsorbent dosing, sample state, and ionic strength of solutions on the adsorption of heavy metals onto bio-adsorbents collected simply from legumes and homemade waste at room temperature and then dried at 65 C0 and ground to size mesh 80-100 microns. Arsenic was not found in the samples studied. The cadmium content of the samples was removed through cooking and treated with a mixture of certain percentages of CBW and RH. The content of Lead and Nickel decreased significantly (p<0.05) in all cooking methods. The weekly cadmium intake in bulk and unprocessed packaged rice samples is higher than that of Iranian national standards. Still, with the new eco-friendly detoxification method, there is no risk under any cooking conditions and no food contamination. The current research findings indicate that Food/Agro waste can be utilized profitably in processing rice containing heavy metal ions.