Abstract
In this study, the kinetics modeling for design of adsorbers for multiple adsorption of heavy metal ions was carried out using activated carbon from waste Nigerian bamboo. The bamboo was cut into sizes, washed, dried and was carbonized at 350°C-500°C. It was then activated at 800°C using nitric acid. Simultaneous batch adsorption of different heavy metal ions (Cd2+, Ni2+, Pb2+, Cr3+,Cu2+and Zn2+) in same aqueous solution using activated carbon from Nigerian bamboo was carried out at different initial concentration till equilibrium was reached. In order to determine the mechanism of sorption for multiple adsorption of these heavy metals ions, the kinetic data were modeled using the pseudo first order, pseudo second order kinetic equations, and intra-particle diffusion models. The pseudo first order did not fit well into the kinetic data. The pseudo second order equation was the best applicable model to describe the sorption process. Hence the pseudo second order kinetic reaction is the rate controlling step with some intra particle diffusion taking place. An empirical model was also developed which can then be used for predicting and designing adsorber for the multiple removal of 99% heavy metal ions at any given initial heavy metal ions concentration and the adsorption time required for any multi-stage adsorption system using Nigerian Bamboo activated carbon.
Highlights
One of the most challenging task in water treatment is simultaneous removal of multi-metal ions in solution
In the removal of chromium(VI) using magnetically modified graphene oxide–chitosan composite, a single stage batch adsorber was proposed for removal of Cr(VI) concentration up to 0.05 mg L−1 [2] while for the removal of Cu(II) from aqueous solutions when clay of the Gulbarga region, Karnataka, India was used as an adsorbent, a two-stage batch adsorber was designed for the removal of Cu(II) from aqueous solutions, which reduced the adsorbent dose by 51% when compared to that of a single-stage adsorption system [3]
In order to understand the possible mechanism for the adsorption of the multiple adsorption of these heavy metal ions in aqueous solution the pseudo first order kinetic model, pseudo second order kinetic model and the intraparticle diffusion kinetic model were used for the sorption kinetic analysis
Summary
One of the most challenging task in water treatment is simultaneous removal of multi-metal ions in solution. Sourcing for a cheap and effective local adsorbent that can selectively adsorbed several heavy metals ions such as cadmium, nickel, lead, chromium, copper, zinc ions (i.e Cd2+, Ni2+, Pb2+, Cr3+, Cu2+ and Zn2+) often found in industrial and refinery waste waters in same solution is important for Nigeria, since the removal of heavy metals ions in solution to acceptable limit nontoxic to the ecosystem is still a challenge. Stirred batch adsorbers are often used in adsorption studied because they offer a number of advantages in comparison to fixed bed systems, as they reduce mass transfer resistances, pressure drops and fouling of the sorbent particles [4]. Minimizing the contact time for a fixed percentage of pollution removal using a fixed mass of adsorbent will result in being able to process more batches of polluted wastewater per day, enabling the required treatment plant items to be reduced in size, with a decrease in the plant capital cost
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