Abstract
The study aims to quantitatively assess the capability of lignin extracted from Saccharum spontaneum L. (talahib grass) as an adsorbent of chromium (III) and phenolphthalein in aqueous solution through kinetic methods. Results show that using lignin as an adsorbent, the percentage removal for both chromium (III) and phenolphthalein in aqueous solution are 31.70% and 74.98%, respectively, based on the optimum exposure time of the adsorbent, which is 6.5 hours for chromium (III) and 60 minutes for phenolphthalein. Results from the mechanistic analysis show that a pseudo-second order adsorption kinetic model fits better than a pseudo-first order model for both substrates. Also, among the six selected adsorption isotherm models used in this study, the Flory-Huggins isotherm can best predict the properties of the adsorption process of both phenolphthalein and chromium (III) at equilibrium. Further improvement of the extracted lignin through various physical and chemical modifications may improve its ability to remove the contaminants.
Highlights
River systems in Meycauayan, Bocaue, and Marilao in Bulacan had high concentrations of chromium, lead, and cadmium coming from tanneries and electroplating industries (Greenpeace, 2007)
Lignin was extracted from Saccharum spontaneum L. using the alkaline method
It was found that the yield of the extraction is consistent at an average of 15.19% by mass, which is within the range of the conditions of the experiment
Summary
Water pollution is a threat facing freshwater reserves available for consumption by organisms. Wastewater produced from anthropogenic processes usually seep to the freshwater sources making it hazardous. Minimizing the concentration of toxic substances (heavy metals, organic effluents, agricultural by-products, inorganic acids) in wastewater and freshwater sources is a crucial step to prevent destruction of the aquatic ecosystem. Common techniques employed to reduce concentration of heavy metals and organic effluents include chemical precipitation, membrane filtration, ion exchange, and adsorption on activated carbon. New treatment methods are currently being developed to reduce the high operational cost of the aforementioned procedures. These methods include adsorption on waste slurry, fly ash, lignite, pine bark, peat, and lignin (Guo, Zhang, & Shan, 2008; Carrott & Carrott, 2007)
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