Trivalent chromium adsorption on activated carbon derived from biowaste: Kinetic, isotherm, and thermodynamic studies

Abstract

The basic chromium sulfate is used in leather tanning to stabilize the collagen protein. In tanning, a large amount of trivalent chromium is released into wastewater, which harms the environment, especially aquatic bodies. This research focuses on the adsorption capacity of trivalent chromium on activated pineapple crown biowaste adsorbent (APCBA). The equipped adsorbent was characterized using an Energy Dispersive X-ray Spectrometer (EDS), Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy, and pHpzc (point of zero charge). A batch assessment was performed for chromium adsorption on APCBA. The trivalent chromium removal efficacy was 98.50 % at an APCBA dose of 0.5 g/50 mL wastewater for a short stirring time (15 min), with a 2 h settling at 30℃ temperature. The reductions in environmental pollutants BOD, COD, and Cl^- were 62.4 %, 55.3 %, and 49.2 %, respectively. The morphological changes of pure and Cr-loaded APCBA were well documented through SEM micrographs and EDS spectra. The presence of functional groups on Cr-loaded APCBA ensures the adsorption of pollutants. The Freundlich isotherm and PSO kinetics of linear fit revealed a good fit for Cr adsorption with correlation coefficient (R²) values of 0.9896 and 0.9999, respectively. Thermodynamic studies indicate the reaction was exothermic and spontaneous. pHpzc assessment of APCBA represents the Cr adsorption mechanism. Therefore, the application of APCBA in wastewater treatment, especially chrome tanning wastewater, is recommended before discharging it into the environment.