Powdered Cogon Grass (Imperata cylindrica) as a Biosorbent for the Removal of Iron (II)

Abstract

Iron (II) sulfate is a compound that is a waste byproduct in metal industries, contributing to excess iron levels present in water bodies. Iron (II) sulfate removal techniques include precipitation, filtration, and oxidation, which are effective but are more complex and costly. These techniques are largely affected by ion solubility, pH level of water, and the presence of other metal ions. Changes in pH can lead to the precipitation of other metal ions present and failure to filter properly may cause them to sediment and sink to the bottom. This research studied the potential of cogon grass (Imperata cylindrica) as a low-cost adsorbent for the removal of ferrous sulfate. Batch adsorption studies resulted in the adsorption capacity ranging around 200-350 mg/g, where increasing adsorbent dose correlated to an increase in percent removal but decrease in adsorption capacity. The percentage removal also increased with higher temperature, while the effect of agitation speed plateaued from 145 RPM above. The adsorption process conforms to pseudo-second-order kinetics with an R2>0.96 and Freundlich isotherm model with R2>0.97. FTIR analysis of cogongrass before and after FeSO4 adsorption shows significant shifts in the IR spectrum, indicating new chemical bond formations, particularly with hydroxyl and carboxyl groups. Initially, peaks were identified for various functional groups like hydroxyls, alkanes, anhydrides, alkenes, and siloxanes. Post-adsorption, notable changes include the shifting and appearance of new peaks in hydroxyl, alkene, lignin, amine, and sulfonic acid bands, suggesting interactions with iron sulfate and the formation of organometallic complexes.