Abstract
In this study, cashew nut shells (CNS), waste from a cashew nut processing factory, have been used as an adsorbent for Pb(II) ions in water. Treatments of CNS with 1 M of H2SO4, HNO3, and NaOH solutions were performed to modify their surfaces and improve their adsorption capacities. Characterization of untreated and chemical-treated CNS was carried out using nitrogen adsorption isotherm, elemental (CHN) analysis, Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX). In the study of Pb(II) removal, various models of adsorption kinetics and isotherms were evaluated against the experimental data. The results showed that H2SO4-treated CNS exhibited the highest adsorption capacity. The chemical treatment removes impurities, alters the surface functional groups and improves specific surface areas and pore volumes of native CNS significantly. Surface adsorption and intra-particle diffusion steps were found to substantially affect the overall adsorption process of Pb(II) on H2SO4-treated CNS. Owing to its easy preparation and comparable adsorption capacity, H2SO4-treated CNS has the potential to be developed as a low-cost adsorbent for the removal of Pb(II) from contaminated water.
Highlights
In this study, cashew nut shells (CNS), waste from a cashew nut processing factory, have been used as an adsorbent for Pb(II) ions in water
Such contaminated water leads to environmental problems and accumulation of heavy metals in the food chain which returns to human beings
In the adsorption process, activated carbon has been widely recognized as an effective adsorbent for the removal of various pollutants contaminated in water
Summary
Cashew nut shells (CNS), waste from a cashew nut processing factory, have been used as an adsorbent for Pb(II) ions in water. Owing to its easy preparation and comparable adsorption capacity, H2SO4-treated CNS has the potential to be developed as a low-cost adsorbent for the removal of Pb(II) from contaminated water. Many methods have drawbacks which are high capital and operating costs, the requirement of extra chemicals and high energy, generation of hazardous sludge, and low performance for diluted wastewater[8]. Among these methods, adsorption is very attractive owing to its easy operation and high efficiency to treat water contaminated with low concentrations of heavy metals, i.e.,
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