Title : Removal of toxic phenol from wastewater using low-cost adsorbents
Phenol being toxic in nature needs to be removed from wastewater before its surface discharge. This research aims for removal of phenol using four biological waste adsorbents guava tree bark, rice husk, neem leaves, activated carbon from coconut coir and four industrial waste adsorbents rice husk ash, red mud, clarified sludge from basic oxygen furnace, activated alumina. The surface characterization of adsorbents were carried out by SEM, XRD, FTIR and BET analyzers. The phenol removal percentage were investigated with the variation of initial phenol concentration (5-500 mg/L), initial pH (2-12), adsorbent dose (0.10-20 gm/L), temperature (25-50°C) and contact time (30-600 min). The maximum removal was obtained as high as 97.50%. The experimental results were used for kinetic, isotherm and thermodynamic studies. The kinetic analysis showed that the pseudo-second order was best fitted for all adsorbents except red mud and the adsorption mechanism was supportive of film diffusion, intra-particle diffusion and chemisorption for all adsorbents. The isotherm analysis suggested that Freundlich isotherm model was best supportive for guava tree bark, rice husk, neem leaves, activated carbon, red mud and activated alumina, whereas Langmuir and D-R isotherm was best supportive for rice husk ash and clarified sludge respectively. The thermodynamics study showed that the adsorption processes were spontaneous, random and endothermic or exothermic in nature. The phenol removal efficiencies with real industrial wastewater collected from a coke oven plant were also studied in this research work. Further the scale-up design, safe disposal and regeneration of adsorbents were carried out to examine their commercial applications. The innovative ANN modeling was also studied which showed that the experimental and predictive data were within allowable range. The research finally reveals that all the adsorbents are substantially effective for phenol removal and can therefore be considered for circular economy.