Influence of impregnation ratio on coffee ground activated carbon as landfill leachate adsorbent for removal of total iron and orthophosphate

Coffee grounds waste was used to prepare activated carbon with particle size between 1.18 and 2 mm by chemical activation with sulphuric acid. The influence of impregnation ratio on physical properties of activated carbon and removal efficiency of total iron and orthophosphate (PO4–P) was studied. Impregnation ratio of 0.5 was found optimum for preparing activated carbon with high pore surface area (224.7 m2/g) and micropore volume (0.07986 cm3/g). Batch experiments were conducted to study the effects of contact time, pH, particle size and adsorbent dosage. Impregnation ratios of 2.5 and 0.5 were found to be optimum for the adsorption of total iron and PO4–P, respectively at doses of 10 g and pH 8.1. pH 13 was optimum for iron removal while pH < 5 and > 11 was optimum for PO4–P removal. The adsorption capacity increased with increasing adsorbent dosage for total iron. However, this trend was exceptional for PO4–P with fluctuating adsorption capacity. The smaller particle size yielded larger adsorption capacity.

Research highlights
► Coffee grounds waste was used to prepare activated carbon with particle size 1.18–2 mm.
► Impregnation ratio of 0.5 was found optimum for preparing activated carbon.
► Impregnation ratio of 2.5 and 0.5 was optimum for the adsorption of Fe and PO4.
► pH 3 was optimum for Fe removal, while pH < 5 and > 11 was optimum for PO4 removal.