ADSORPTION STUDIES FOR THE REMOVAL OF CHROMIUM (CR2+) FROM A BREWERY EFFLUENT USING ACTIVATED CARBON PREPARED FROM AFRICAN PEAR SEED (DACRYODES EDULIS)

ABSTRACT The rise in industrial productivity has increased the discharge of wastewater containing toxic heavy metals, which pose significant risks to humans and the environment. Addressing this issue requires effective treatment methods, with adsorption being a highly efficient approach. This research focuses on using agricultural waste-derived adsorbents to remove chromium from brewery effluent, offering a sustainable and locally available solution. In this study, wastewater was collected from a brewery industry and was analysed to detect the presence of Chromium (Cr2+) which was removed using activated carbon produced from African pear seeds (Dacroydes edulis) using batch adsorption process. The activated carbon was obtained by carbonizing at a temperature of 500℃ in a muffle furnace, impregnated with 30% concentration of H3SO4 acid and activated at a temperature of 600℃ for 2hours. The African Pear Seed Activated Carbon (APSAC) was characterized using proximate analysis, Fourier transform infra-red spectrophotometer (FT-IR) analysis and scanning electron microscope (SEM) analysis to determine the physiochemical properties, functional groups and surface morphology respectively. The effect of various adsorption parameters; contact time (15-75min), initial solute concentration (0.05-0.25mg/L), adsorbent dosage (0.5-2.5g) were investigated. The experimental result showed maximum chromium percentage removal of 96% at concentration of 0.025 mg/L, dosage of 1.5g at 45 minutes. The interactive effects of the percentage removal showed an increase with higher adsorbent dosage but decreases with an increase in the initial concentration. The percentage removal increased with both adsorbent dosage and contact time, but the increase levelled off on reaching reaction equilibrium. Similar variation was observed with adsorption capacity. The result from design expert showed that the Sips model clearly outperformed all other models in terms of correlation coefficient. This high R² suggests that the Sips isotherm model described this process best. Also, surface adsorption was the dominant driving force while chemisorption, which involved electron sharing or exchange between Cr²⁺ ions and APSAC, was also an effective mechanism considering the R-squared values. The significant adsorption capacity and percentage adsorption shows how effective APSAC can be in treating heavy metals present in wastewater.