Chemically activated carbon preparation from natural rubber biosludge for the study of characterization, kinetics and isotherms, thermodynamics, reusability during Cr(VI) and methylene blue adsorption. (18th January 2023)

• Record Type: Journal Article
• Authors: Mahapatra, Uttara; Chatterjee, Abhijit; Das, Chandan; Manna, Ajay Kumar
• Is Part Of: Water science and technology. Volume 87:Number 3(2023)
• Page Start: 635
• Page End: 659
• Publication Date: 2023-01-18
• Subjects: adsorption–desorption -- chemical activation -- heavy metal -- intra-particle diffusion -- modeling -- wastewater; Water -- Pollution; Sewage -- Purification; Water quality management; Periodicals; 628.168
• DOI: 10.2166/wst.2023.004
• Languages: English
• ISSNs: 0273-1223

Abstract

Abstract: Alkaline leachate, dust generation, and foul smell during the stacking process of natural rubber biosludge (NRBS) can pollute surrounding water, soil, and air. In this study, natural rubber chemically activated carbon (NRCAC) has been synthesized for the first time from NRBS by pyrolysis using ZnCl2 at 700 °C for adsorptive removal of Cr(VI) and methylene blue (MB) from aqueous solutions. Both NRBS and NRCAC were characterized by X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), Brunauer–Emmett–Teller (BET), and thermogravimetric analyzer (TGA). FTIR and SEM-EDS suggested significant functional and morphological transformations in NRCAC. Experimental investigations of different process parameters, such as pH, concentration, contact time, salt concentration, etc., were conducted to study their influences on adsorption. Adsorption and desorption kinetics followed a pseudo-second-order model, while adsorption equilibrium followed Liu isotherm. Maximum uptake calculated from the Liu model was 81.28 and 211.90 mg/g for Cr(VI) and MB, respectively. Thermodynamic analysis established spontaneous and endothermic adsorption. Up to five adsorption/desorption cycles were conducted using eluents such as 1 M NaOH and water for Cr(VI) and MB, respectively. Electrostatic attraction and ion-exchange favored Cr(VI)/MB adsorption, while hydrogen bonding and π–π stacking were significant in MB uptake. Overall findings suggest that NRBS (a renewable agro-industrial, abundant, and freely available) could be employed to synthesize biochar for adsorptive removal of wastewater containing Cr(VI)/MB. HIGHLIGHTS: Natural rubber chemically activated carbon (NRCAC) was prepared for first time from natural rubber biosludge (NRBS). BET surface area of 4.62 and 414.16 m 2 /g was reported for NRBS and NRCAC, respectively. Maximum experimental uptake of Cr(VI) and MB by NRCAC was 78 and 203 mg/g, respectively. NaCl and CaCl2 showed a negative effect on Cr(VI) removal but a positive effect on MB removal. Five regeneration cycles of NRCAC using 1 M NaOH for Cr(VI) and water for MB. Graphical Abstract