LASER- ASSISTED BIOMASS-BASED ACTIVATED CARBON: PREPARATION AND APPLICATIONS

Abstract

This study evaluated the use of Laser-Treated Activated Carbon derived from waste biomass, namely, date stones in the fields of energy storage and wastewater treatment. For these purposes, electrochemical double-layer capacitor (EDLC) assembly and Methylene Blue contaminated water were used. In this work, biochar was prepared from waste date stones through thermal carbonization process under nitrogen purge. It was chemically activated using Zinc Chloride (ZnCl2) and Potassium Hydroxide (KOH) with 1:2 impregnation weight ratio separately. Prepared powder was then laser-treated using pulsed Nd-YAG laser at its fundamental frequency (1064 nm). All laser-treated samples outperformed non-treated ones in porosity measurements especially specific surface area, micro and meso-porosities. They also showed improved surface chemistry in the form of newly developed oxygen containing functional groups. SEM micrographs revealed that laser-treated samples showed higher surface roughness coinciding with X-ray diffractograms which showed lower crystallinity ratios. For energy storage, laser-treated ZnCl2 activated carbon electrodes outperformed non-treated ones in different electrochemical tests. They showed 80% enhancement in specific capacitance, 21% reduction in equivalent series resistance, longer charging-discharging time and enhanced capacitance retention over 10000 cycles. For wastewater treatment, laser-treated KOH-activated carbon outperformed non-treated counterparts in methylene blue (MB) adsorption following Langmuir, Freundlich and Temkin isotherms. It also showed improved kinetics following pseudo 2nd order (PSO) model. Specifically, laser-treated samples showed about 350%, 398%, 369% and 406% enhancements in qmax, PSO kinetics, heterogeneity and initial adsorption rate respectively. Both testing regimes emphasize the efficacy of implanting pulsed laser energy as a single step post treatment method for tailoring the characteristics of chemically activated carbon.