High surface area and supermicroporous activated carbon from capsicum (Capsicum annuum L.) industrial processing pulp via single-step KOH-catalyzed pyrolysis: Production optimization, characterization and its some water pollutants removal and supercapacitor performance

Abstract

In this study, we aimed to convert capsicum (Capsicum annuum L.) industrial processing pulp (CP) into low-cost and high-quality activated carbon (AC) under optimal production conditions through single-step KOH-catalyzed pyrolysis. Optimal production conditions were determined by investigating the effects on some textural characteristics of the produced ACs by changing the process variables such as mixing ratio (KOH/CP, w/w), pyrolysis temperature, and pyrolysis duration, respectively. The AC (CPAC) with the BET (Brunauer-Emmett-Teller) highest surface area (1564 m2/g), pore-volume (0.623 cm3/g), and average pore size (1.8 nm) was produced under conditions with a mixing ratio of 1.5, a pyrolysis temperature of 700 °C, and a duration of 1 h. It was characterized by nitrogen adsorption/desorption, Scanning Electron Microscopy (SEM)/Energy Dispersive X-Ray (EDX), X-ray Diffraction (XRD), Raman Microscopy and Fourier Transform Infrared Spectroscopy (FT-IR) techniques. In addition, the adsorption ability was determined by examining the removal performance of water pollutants such as methylene blue (MB) and methanol yellow (MY) dyes, 2,4-dichlorophenoxyacetic acid herbicide (2,4-D), diclofenac sodium drug (DCF), copper(II) ion (Cu(II)), and nitrate (NO3−), which were chosen because they are frequently detected in industrial wastewater, and found to be 294.1, 370.4, 384.6, 294.1, 212.8 and 59.5 mg/g, respectively. The supercapacitor performance of the electrodes developed from CPAC was tested as the coin size cell. The gravimetric capacitances of the electrodes were calculated as 198 F/g at the current densities of 0.5 A/g. The results of this study reveal that CPAC can be used as an alternative to commercial carbon as a clean and ecologically compatible low-cost (~$1.75 per kg) adsorbent that can improve water quality, and promising electrode material for low-cost and high-performance carbon-based supercapacitors.