Adsorption kinetics and intraparticulate diffusivities of Hg, As and Pb ions on unmodified and thiolated coconut fiber

Abstract

ABSTRACT:As, Hg and Pb are examples of heavy metals which are present in different types of industrial effluents responsible for environmental pollution. Their removal is traditionally made by chemical precipitation, ion-exchange and so on. However, this is expensive and not completely feasible to reduce their concentrations to the levels as low as required by the environmental legislation. Biosorption is a process in which solids of natural origin are employed for binding the heavy metal. It is a promising alternative method to treat industrial effluents, mainly because of its low cost and high metal binding capacity. The kinetics was studied for biosorption experiments using coconut fiber for As (III), Hg (II) and Pb (II) ions adsorption. The specific surface area and surface charge density of the coconut fiber are 1.186x10 25 (m 2 /g) and 5.39 x10 24 (meq/m 2 ), respectively. The maximum adsorption capacity was found to be the highest for Pb (II) followed by Hg (II) and As (III). The modification of the adsorbent by thiolation affected the adsorption capacity. Equilibrium sorption was reached for the metal ions at about 60 min. The equilibrium constant and free energy of the adsorption at 30 ºC were calculated. The mechanism of sorption was found to obey the particlediffusion model. The kinetic studies showed that the sorption rates could be described by both pseudo first-order and pseudo second-order models. The pseudo second-order model showed a better fit with a rate constant value of 1.16 x 10 -4 /min. for all three metal ions. Therefore, the results of this study show that coconut fiber, both modified and unmodified, is an efficient adsorbent for the removal of toxic and valuable metals from industrial effluents. Key words: Adsorption kinetics, intraparticulate diffusivity, heavy metal, coconut fiber, waste management INTRODUCTIONAs, Hg and Pb have detrimental effects on human, plants and animals. The toxicity of these heavy metals to marine life and consequently to man has been established for many years. The sources of As pollution come from discharges of various industries, such as smelting, petroleum-refining, pesticides, herbicide, glass and ceramic manufacturing industries (Volesky and Holan, 1995). Pb pollution particularly results from battery manufacturing, automobile exhaust fumes and metal finishing industries. Hg pollution results from metallurgical industries, chemical manufacturing and metal finishing industries. Other sources of these heavy metals also exist and these have increased as a result of an increase in urbanization and industrialization. The chemistry of these heavy metals is complex and interesting,

Fungal biosorption – an alternative to meet the challenges of heavy metal pollution in aqueous solutions

“…Biosorbents of plant origin are mainly agricultural byproducts such as maize cob and husk [38][39][40][41] . The wide range of algal biosorbents includes microalgae and macroalgae from marine and fresh water sources.…”

Uptake of Indosol Dark-blue GL dye from aqueous solution by water hyacinth roots powder: adsorption and desorption study

“…Natural materials or the wastes, by-products of industries or synthetically prepared materials, which are cheap and can be used as such or after some minor treatment as adsorbents, are generally called low-cost adsorbents. Among natural materials Posidonia oceanica leaf (Ncibi et al 2007;Igwe et al 2008), burnt clay (Mumin et al 2007), tendu waste (Nagda and Ghole 2009), banana peel, orange peel, bagasse pith, rice husk, sawdust, etc., have been shown to give satisfactory results in removal of commercial dyes from aqueous solution (Gupta and Suhas 2009;Ozcan and Ozcan 2004). In Bangladesh, water hyacinth has no competitive use and is considered to be an undesirable species on inland waterways.…”

Adsorption of copper, nickel and lead ions from synthetic semiconductor industrial wastewater by palm shell activated carbon

“…A number of adsorbent materials have been studied for their ability to remove heavy metals and they have been sourced from natural materials and biological wastes of industrial processes (Igbinosa and Okoh, 2009). These materials including: activated carbon (Uzun and Guzel, 2000;Goel et al, 2005;Issabayeva et al, 2007;Mondal et al, 2008), chitosan and carrageenan (Bong et al, 2004), lignite (Allen et al, 1997), kaolinite and ballclay (Chantawong et al, 2003), diatomite (Ulmanu et al, 2003), coconut fiber (Igwe et al 2007) and limestone (Aziz et al, 2004). However, adsorption by activated carbon had been reported as a technically and economically viable technology for heavy metal removal (Huang and Morehart, 1991;Bong et al, 2004).…”