Phenol removal from wastewater using low-cost natural bioadsorbent neem (Azadirachta indica) leaves: Adsorption study and MLR modeling

This research aims to experiment with the potential of neem (Azadirachta indica) leaves for phenol adsorption. Morphology, functional groups, etc. characterize the adsorbent. Batch studies are conducted at pH (2-7), dose (7-12 g/L), time (60-360 min), initial concentration (100-500 mg/L), and temperature (30-50 degrees C). Maximum 97.5% phenol is removed when pH, dose, time, temperature, and phenol concentration is 3, 10 g/L, 240 min, 30 degrees C and 100 mg/L, respectively. Experimental results are supported by pseudo-second-order (r(2) = 0.99999). Kinetic testing is supported by adsorption mechanisms developed by Elovich, Reichenberg, Boyd, Furusawa and Smith, and Fick models. Freundlich model (r(2) = 0.99648) is fitted well compare to other models. Sorption energy (0.5288 kJ/mol) supports physical adsorption. Thermodynamics has suggested for a non-random, exothermic, and spontaneous process. The multiple linear progressing (MLR) modeling has successfully predicted the removal percentage. Desorption with ethanol has revealed 58.5% phenol removal potential. Safe disposal of the used adsorbent is recommended by incineration. The scale-up design has demonstrated that 27.925 kg adsorbent is required for 1000 L wastewater to reduce phenol from 100 ppm to 0.06 ppm in two stages. The novel study concludes that the natural, low-cost bio-adsorbent neem leaves can suitably be used in the refineries and other allied chemical industries for phenol remediation.