Removal of Heavy Metals Using Rice Husk: A Review

The importance of removal of heavy metals from drinking water has received significant attention of researchers and decision makers across the globe. Bio-adsorbents have emerged as potential remediation materials for the removal of heavy metals and metalloids from both groundwater and surface water. Plants, algae, fungi are some of the biomass derived adsorbents which are capable of removing heavy metals and metalloids from aqueous solution by adsorption. For increasing the adsorption efficiency of bio-adsorbents, treatment of adsorbents is done by using various kinds of treating agents like tartaric acid, NaOH. The bio-adsorbents have affinity for heavy metal ions to form metal complexes or chelates due to having functional groups including carboxyl, hydroxyl, imidazole, sulphydryl, amino, phosphate, sulfate, thioether, phenol, carbonyl and amide etc. Rice husk (RH) is a low cost (agricultural by-product) bio-adsorbent which has been studied intensively for the removal of various heavy metals and metalloids (such as Pb, Cd, Zn, Ni and As) from both groundwater and surface water. The present study is focused on critical review of previous and current available information on potential of treated and untreated rice husk for the removal of heavy metals and metalloids (arsenic). Various studies on adsorption efficiency of rice husk considering the parameters contact time, adsorbent dose (rice husk), initial concentration of heavy metals, pH, and temperature have been evaluated by many researchers. The present study analyzed those studies and compiled the adsorption efficiency of rice husk and concluded that treated rice husk gave comparatively better adsorption efficiency of heavy metals with compared to that of untreated rice Sneh Lata & S.R. Samadder 166 husk. The treated rice husk can be implemented on large scale industrial applications after field studies.