In Situ Modification of Activated Carbons by Oleic Acid under Microwave Heating to Improve Adsorptive Removal of Naphthalene in Aqueous Solutions

This study aimed to improve the adsorption capacity of activated carbon (AC) towards naphthalene (NAP) in aqueous solutions. Starch-based AC (SAC) and pulverized coal-based AC (PCAC) were prepared in a one-pot procedure by activation with oleic acid and KOH under microwave heating. Brunauer-Emmett-Teller (BET) specific surface areas reached 725.0 and 912.9 m(2)/g for in situ modified SAC (O-SAC1) and PCAC (O-PCAC1), respectively. pi-pi bond, H-bond, and hydrophobic effects were directly involved in the NAP adsorption process. Batch adsorption data were well fitted by pseudo-second order kinetics and the Freundlich isotherm model. As compared to ACs prepared with only KOH activation, NAP adsorption capacities of PCAC and SAC prepared by the one-pot method increased by 16.9% and 13.7%, respectively. Influences of varying factors were investigated in column adsorption of NAP using O-SAC1 and O-PCAC1. Based on breakthrough curves analysis, the larger column height (H), lower flow rate (Q(0)), and lower initial concentration (C-0) resulted in the longer breakthrough and exhaustion times in both cases. Specifically, we concluded that O-PCAC1 exhibits better adsorption capacity than O-SAC1 in the given conditions. The optimized operating parameters were 1 cm (H), 1 mL/min (Q(0)) and 30 mg/L (C-0). Finally, column adsorption data could be well fitted by the Thomas model.

Automated summary

This study aimed to enhance the adsorption capacity of activated carbon for naphthalene in aqueous solutions by preparing starch-based and pulverized coal-based activated carbons through a one-pot activation method. The findings showed that the pi-pi bond, H-bond, and hydrophobic effects played crucial roles in the adsorption process of naphthalene. Additionally, the optimized operating parameters were determined for effective column adsorption using the Thomas model.