ADSORPTION OF CONGO RED ON BIOCHAR PRODUCED FROM WATERMELON AND ORANGE PEELS

The aim of this study was carried out to investigate the feasibility and effectiveness of using biochar derived from watermelon and orange peels. The collected watermelon and orange peels were washed and dried, then grounded into powder with motor and paste, then soaked in 2% NaOH solution for 24 h. After 24 h, the peels were washed with deionized water until neutral, put into an oven at 80 °C until completely dried, then activated for 24 h at room temperature by adding 85% phosphoric acid solution at a solid to liquid ratio of 1 : 4. The activated peel was put into a crucible and charred in a muffle furnace at 500 °C for 2 h. The powder was cooled to room temperature and passed through a 200 mesh sieve to obtain black powder. The result show the effect of varying adsorbent dosages on the adsorption of Congo red by biochar from orange peels. The initial concentrations of Congo red ranged from 10 ppm to 40 ppm, and the corresponding percentage removal and amount adsorbed were recorded. At 10 ppm, 36.4% of Congo red was removed, with an amount adsorbed of 0.107 mg/g. As the concentration increased to 40 ppm, the removal efficiency decreased to 23.45%, and the amount adsorbed was 0.384 mg/g. The effect of contact time on the adsorption process. The results indicate a significant increase in the removal percentage with prolonged contact time. At 10 ppm, the removal rate was highest at 63.2%, and the amount adsorbed increased to 0.051 mg/g. At higher concentrations, 40 ppm, the removal rate dropped to 14.9%. The study demonstrates that biochar produced from watermelon and orange peels is an effective adsorbent for the removal of Congo red from aqueous solutions. Both biochars show higher adsorption capacities at lower concentrations of Congo red, with diminishing returns as the concentration increases. The results established adsorption isotherms, indicating the saturation of available adsorption sites at higher pollutant loads.