Bioadsorbents and Filters for Removal of Heavy Metals in Different Environmental Samples-A Brief Review

To eliminate the problem of heavy metals, there are naturally occurring materials that are locally and commonly found and are very much encouraged as low cost adsorbents such as industrial and agricultural wastes. Several agricultural and industrial wastes as potential adsorbents have been viewed, which includes wood ash and bone ash, cassava waste, chitosan-g-poly (butyl acrylate)/bentonite nano composite, Eucalyptus tereticornis bark, sarooj clay, orange fruit peel, fly ash, potato peels, coconut shell charcoal, pecan shells, bagasse fly ash, waste sludge, pith and saw dust, maize cob and husk, hazelnut shell, soybean hull, jackfruit, crab shell, neem leaves, cooked tea dust, teak leaves, cashewnut shells, aerogel carbon, sewage sludge ash and lignite-based fly ash. The adsorption details of these adsorbents have been keenly viewed and judged in batch studies mostly. The judgment is on the basis of adsorption isotherms, thermodynamics and parameters like contact time, adsorbent dosage, pH, initial metal concentration and adsorption capacity. Hence, it is proved from the review of these adsorbents that they are highly selective in terms of separation, thermally and mechanically stable and do not foul, regenerative and less soluble in liquids. They are commonly available and are very less costly with removal efficiency up to 99%. The usage of these adsorbents is better applicable at low pH and oxidized or carbonized or activated before using them as adsorbents to remove heavy metal ions from agricultural, industrial and municipal wastes.