Adsorption of Cadmium (II) by Chemically Treated Oil Palm Empty Fruit Bunch

Hafizah, Naihi (2023) Adsorption of Cadmium (II) by Chemically Treated Oil Palm Empty Fruit Bunch. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Oil palm empty fruit bunch (OPEFB) waste disposal and Cadmium (Cd) pollution in waterways issues had affected the community areas nearby the oil palm production. This study aims to investigate the chemical composition, surface morphology, elemental composition, thermal stability, and surface area of the raw and sodium hydroxide (NaOH) treated OPEFB, to evaluate Cd (II) removal percentage and adsorption capacity of the raw and NaOH treated OPEFB at different initial solution pH, adsorbent dosage, agitation speed, temperature, contact time, and initial Cd (II) concentration, and to analyse the adsorption kinetics, isotherm, and thermodynamic parameters of the Cd (II) adsorption onto the raw and NaOH-treated OPEFB. The alkali treatment was done by varying the NaOH concentration and immersion time and 24h-1.0M-OPEFB was chosen as the best adsorbent based on its highest Cd (II) removal percentage, 64.5%. The batch experiment was running over wide ranges of settings and the best conditions of the adsorption process were found to be the pH of 6, the adsorbent dosage of 0.03 g/100 mL, the agitation speed of 150 rpm, the contact time of 90 minutes, the Cd (II) initial concentration of 5 mg/L, and the temperature of 45 C with 85.1% and 88.07% of Cd (II) removal percentage for raw and NaOH-treated OPEFB, respectively. The Fourier Transform Infrared (FTIR), Scanning Electron Microscopy and Energy-Dispersive X-ray (SEM-EDX), Brunauer-Emmett-Teller (BET), and Thermogravimetric (TGA) analysis showed that the treated OPEFB has better intensities of -OH groups (7.3% increment), O/C ratio (44.8% increment), pore-volume (7 times higher), and thermal stability (10.2% lower weight loss) that could provide higher metal binding sites. The experimental data obtained are better described by the Pseudo-second-order (chemisorption mechanism); Raw OPEFB: R2=0.99992, NaOH-treated OPEFB: R2=0.99991 and Freundlich (multilayer adsorption) models; Raw OPEFB: R2=0.98789, NaOH-treated OPEFB: R2=0.97541, and the maximum adsorption capacity for raw and treated OPEFB was 35.82 mg/g and 37.68 mg/g, respectively. The thermodynamic adsorption study indicated that the adsorption reaction was spontaneous; Raw OPEFB: ΔG° =-25807.00 to -28725.91 kJ/mol, NaOH-treated OPEFB: ΔG° =-26417.89 to -29397.08 kJ/mol. Moreover, raw and NaOH-treated OPEFB adsorbents exhibit highly effective Cd (II) sorption capacities in both single system and binary systems (Cd (II) - Zn (II) and Cd (II) - Pb (II), can be used fruitfully for three reuse cycles by using 0.1 M HCl; Raw OPEFB: % desorption= 4.11-11.16%, NaOH-treated OPEFB: % desorption= 8.78-17.20%, and they have higher removal efficiency as compared to the commercial coconut activated carbon.

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