Adsorptive removal of 2,4,6-trichlorophenol in aqueous solution using calcined kaolinite-biomass composites

•Calcined biomass modified kaolinite clay composite adsorbents were prepared.•The composites had faster adsorption rates (less than 30 min).•The composites had higher adsorption efficiencies (up to 250% more than kaolinite).•Low-cost composite adsorbents may be useful for effluent treatment.

Synergistically combined low-cost composites may be effective for the potential treatment of effluents containing organic pollutants. Hence, preparation of Carica-papaya-modified-kaolinite (CPK) and pine-cone-modified-kaolinite (PCK) composites via calcination of pure kaolinite (KAC), Carica-papaya and pine-cone seeds is demonstrated. The composites' specific surface areas were reduced by more than 57% but no structural modification in KAC lattice d-spacing, indicating impregnation of calcined biomass on clay surfaces and pores. However, composites' cation exchange capacities were enhanced over 4-fold, indicating higher potential for adsorption. Adsorption of 2,4,6-trichlorophenol on composites and KAC showed that CPK and PCK attained equilibrium relatively faster (30 min) compared to KAC (60 min). Modeling studies showed that 2,4,6-trichlorophenol removal mechanisms involved electrostatic interactions on sites of similar energy. Modification enhanced adsorption by 52 and 250% in PCK and CPK, respectively, and adsorption increased with temperature.

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