Phenol being a severe environmental pollutant needs to be removed from wastewater before its surface discharge. Adsorptive removal of phenol is gaining popularity due to its low cost and many researchers are still focusing on the application of new adsorbents. This research aims for phenol removal by four bio-adsorbents viz. guava tree bark, rice husk, neem leaves and activated carbon from coconut coir and four industrial waste adsorbents viz. rice husk ash, red mud, clarified sludge from basic oxygen furnace and activated alumina. The surface characterization of the adsorbents were carried out by SEM, XRD, FTIR and BET analyzers. The phenol removal percentage was 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 removal percentage was obtained as high as 97.50%. The kinetic study showed that the pseudo-second order was best fitted for all adsorbents except red mud. The kinetic testing showed that 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 showed that the spontaneity, randomness and endothermic/exothermic nature of the adsorption process were different but conclusive. The ANN modelling using two popular algorithms viz., Levenberg-Marquardt and Scaled Conjugate Gradient established that the experimental and predictive data were within the allowable range. The scale-up designs and the safe disposal of used adsorbents were also studied for their commercial applications. The research concludes that the adsorbents used in this study are effective for phenol removal and also for circular economy in many countries.