Abstract
Microcrystalline cellulose (MCC) was modified with 1, 2, 3, 4-butanetetracarboxylic acid (BTCA) to obtain the adsorbent material named treated microcrystalline cellulose (TMCC), which was characterized for point of zero charge (pHZPC), estimation of carboxyl group content and surface group moieties, surface morphology and textural properties. Application of TMCC for the removal of Hg(II) ions from aqueous solution was studied with respect to carboxyl group content, and process parameters, including adsorbent dose, initial solution pH, temperature, contact time, and Hg(II) ion concentration, to provide information about the adsorption mechanism. Isothermal adsorption data were analysed using a range of two and three parameter adsorption models, with the level of fit determined using nonlinear regression analysis. The maximum adsorption capacity under optimised conditions was determined using Langmuir analysis and found to be 1140 mg/g, and Freundlich analysis showed that adsorption of Hg(II) ions onto TMCC is favourable. The kinetic results using a range of models, showed that a pseudo-second order kinetic model was most appropriate for the data obtained, which indicates that the process involves chemisorption. The results obtained show TMCC to have a high affinity for Hg(II) ions from aqueous media, which suggests that these materials may have potential for application in water treatment systems.
Highlights
Water contamination, due to elevated levels of large quantities of toxins or substances, such as harmful heavy metal ions, inorganic anions, micropollutants, organic compounds such as dyes, phenols, pesticides, humic substances, detergents, and other persistent organic pollutants, has been widely documented in various parts of the world in recent decades
The spectrum obtained for treated microcrystalline cellulose (TMCC) loaded with Hg(II) ions show a shift in peaks observed at observed at 1715, 1645, 1317, 662, 592 and 555 cm-1 to 1714, 1644, 1316, 6621, 588 and 554 cm-1, and new peaks at 1202, 1026, 890 and 439 cm-1, which are attributable to the qualitative observation of the adsorption of Hg(II) ions onto the adsorbent
3.7 Mechanism of adsorption The data obtained in this study indicate that the TMCC adsorbent is rich in carboxylic functionalities on its surface, which, at the pH used here, has a negative charge that attracts the positively charged Hg(II) ions from aqueous solution
Summary
Due to elevated levels of large quantities of toxins or substances, such as harmful heavy metal ions, inorganic anions, micropollutants, organic compounds such as dyes, phenols, pesticides, humic substances, detergents, and other persistent organic pollutants, has been widely documented in various parts of the world in recent decades. Research has focussed on developing low cost, environmentally friendly materials for water and wastewater treatment, with no hazardous process byproducts, resulting in increased attention towards natural bio-based materials, which offer high uptake capacities, reduced sludge generation, regenerative potential, and abundant availability globally [9]. One such material is microcrystalline cellulose, which is biodegradable, has good mechanical strength, and high thermal stability [10]. The adsorption capacity of this raw material has been enhanced by chemical modification of the cellulose backbone through chemical modification [11] . where chemical reactions (e.g. esterification, etherification, amination), graft copolymerization, or physicochemical modification (e.g. thermal or mechanical reinforcements) [12] can be utilised
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