Production of activated carbons from wastes for water treatment

Abstract

To address the global challenge of increasing waste generation, this current research is dedicated to waste management and enhancing its commercial value through pyrolysis and activation techniques. The literature review encompasses experimental and model-based investigations on using mixed wastes for pyrolysis, activation, and implementation for water treatment. Specifically focusing on Qatar, where the oil and gas sector is rapidly expanding, leading to a substantial increase in waste and produced water, this thesis centers on the utilization of three feeds: GTL-derived biosolid (BS), a major municipal solid waste cardboard (CB), and mixed samples (50:50). The initial phase of the study primarily involves a parametric analysis during the pyrolysis process to gain insights into the yield and characteristics of the produced biochar. Subsequently, a comprehensive comparative analysis of the surface morphology and chemical composition is conducted between the raw feed, biochar, and single-stage activated carbon (AC) (using potassium carbonate), focusing on identifying potential applications. All three activated samples were effectively employed for the removal of methylene blue (MB) and metals strontium (Sr) and barium (Ba), which are notably present in produced water. The mixed AC (KM) (SA: 524 m2/g) exhibited the highest adsorption capacities across all scenarios, reaching 191, 91.05, and 99.02 mg/g for MB, Sr, and Ba in a single system while achieving 80.56 and 90.01 mg/g for Sr and Ba in a binary system. Isotherm, kinetic modelling, and thermodynamic calculations were carried out for both adsorption systems- based on these results, mechanisms were proposed for both cases. More importantly, the regeneration of spent KM of up to three rounds was successful for both adsorption systems. The economics revealed a payback period of 3.99 years and a levelized cost of $2.84/kg for AC production. The final section of the thesis is dedicated to exploring the potential of biochar samples derived from GTL biosolid (BS), highlighting their reduced environmental risks, and leaching when compared to the original feed material. Moreover, a two-stage physical activation process was conducted in a CO2-rich environment for all three biochar samples (BS, CB, and mixed). This resulted in the mixed sample achieving the maximum surface area (SA: 502 m2/g). The novel findings presented in this thesis offer a sustainable approach to managing solid waste while concurrently developing materials suitable for water treatment, thereby presenting a dual-pronged strategy for pollution management.

Date of Award	2023
Original language	American English
Awarding Institution	HBKU College of Science and Engineering