Abstract
Adsorption of lead ions from aqueous solutions onto various waste biomass materials was studied. Coir pith, saw dust, rice husk, rice bran and tea waste were tested for Pb ion adsorption to enable comparison with alternative commonly used adsorbent granular activated carbon. Batch experiments were conducted to determine the adsorption capacities and kinetics of the process. All the waste biomass materials tested were capable of binding appreciable amounts of Pb ions from aqueous solutions. Adsorption capacities were in the order, coir pith> tea waste> activated carbon> rice bran> saw dust> rice husk. The equilibrium data were satisfactorily fitted to Langmuir and Freundlich isotherms. Langmuir monolayer adsorption capacities for coir pith, tea waste and granular activated carbon were 72, 65 and 28 mg/g respectively. Kinetic studies revealed that Pb uptake was fast with 90% or more of the adsorption occurring within first 15 to 20 min of contact time. The kinetic data fits to pseudo second order model with regression coefficients greater than 0.99. Fixed bed column experiments were performed to study practical applicability and breakthrough curves were obtained. Column operations showed lower adsorption capacities than the batch operation. Amount of Pb adsorbed in the column operations were 46, 41 and 19 mg/g for tea waste, coir pith and granular activated carbon respectively.
Highlights
Heavy metals are continuously released into the water streams from industrial processes
Adsorption of lead cations occurs as a result of physicochernical interaction, mainly ion exchange or complex formation between metal ions and the functional groups present on the cell surface
The results show that adsorption onto Coir pith and Tea waste are faster compared to that of GAC
Summary
Heavy metals are continuously released into the water streams from industrial processes. Finds extensive applications in day-to-day commodities like batteries, paints, ceramics, soldering etc. It is an essential component for production of many other highly technical products. Water streams get contaminated with lead, due to inappropriate waste disposal practices. Lead is a very toxic element even at low concentrations. It affects the central nervous system, kidneys, gastrointestinal system etc [14]. Due to the increased awareness about environmental and health aspects many countries have imposed stringent environmental laws and treatment of the effluent streams has got exceptionally great importance nowadays [5]
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