Phosphoric acid modified activated carbon prepared from Fox nutshell for adsorption of phenol: batch and continuous studies

The advancement in industrial and agricultural activities and the discharge of improperly treated effluent increase the pollution load on the environment. In this regard, organic contamination has posed a severe concern; among various organic pollutants, phenol is a highly toxic pollutant. For the adsorption of phenol, a low-cost activated carbon (AC) was prepared from fox nutshell using H3PO4 as an activating agent in a N2 atmosphere. Fox nutshell is an agricultural waste containing only 5% ash content, which is beneficial for the adsorption of phenol. The optimum conditions used for preparing AC were: 1 h of carbonization time, 700 oC of carbonization temperature, and a 3:1 impregnation ratio. The prepared AC is named ACPA-700-1.5. The physicochemical properties of prepared ACPA-700-1.5 were: yield 30.38%, average pore diameter 2.32 nm, pore volume 1.53 cm3/g, and surface area 2636 m2/g. Finally, batch and fixed-bed column adsorption tests were performed using ACPA-700-1.5. The best-fitting isotherm model was the Freundlich isotherm model, indicating heterogeneous adsorption. Pseudo-second-order was the best-fitting kinetics model. The results showed that the prepared ACPA-700-1.5 exhibited a maximum capacity of 101.83 mg/g. The column adsorption study showed that a lower flow rate and a higher bed height were suitable for maximum adsorption performance. The maximum bed capacity of 75.64 mg/g was achieved at a bed height of 4 cm and a flow rate of 5 mL/min. Given its high adsorption capacity and extremely fast adsorption rate, ACPA-700-1.5 is a promising adsorbent for removing phenolic contaminants from wastewater.