Applicability of plant based biosorbents in the removal of heavy metals: a review

Heavy metals are toxic, persistent, carcinogenic and mutagenic in nature. Industrial wastewater is a widely known source for metal pollution in aquatic bodies as well as surface contamination. There are various techniques available for the removal of heavy metals from wastewater, like ion-exchange, membrane filtration, electrolysis, coagulation, flotation, and adsorption. However, these methods have several disadvantages like high operating cost, sludge generation and selectivity of metals. Among them, adsorption processes are extensively used for heavy metal and other pollutant removal. Biosorption is an eco-friendly, sustainable, rapid and economic process, which increases its wide application. Biosorbents are easily available and low cost in nature. Plant biomasses are commonly used as biosorbents for synthetic and real wastewater treatment. The adsorbent capacity of metal ion removal varies, depending on the nature of the adsorbent, pH, contact time, particle size, and metal concentrations. In this review paper, literature on plant based biomass has been compiled to provide concise information exploring the adsorption efficiencies in removal of toxic metals like cadmium, copper, lead, mercury, cobalt, chromium, arsenic, zinc and nickel. The metal removal efficiencies in batch and column studies are also compared.