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Adsorption, Kinetics and Equilibrium Studies on Removal of Catechol and Resorcinol from Aqueous Solution Using Low-Cost Activated Carbon Prepared from Sunflower (Helianthus annuus) Seed Hull Residues

Vunain, Ephraim, Houndedjihou, Dégninou, Monjerezi, Maurice, Muleja, Adolp Anga, Kodom, BarthélémyTomkouani
Water, air, and soil pollution 2018 v.229 no.11 pp. 366
Fourier transform infrared spectroscopy, Helianthus annuus, X-ray diffraction, activated carbon, adsorbents, adsorption, agricultural wastes, aqueous solutions, benzene, catechol, endothermy, energy-dispersive X-ray analysis, kinetics, models, moieties, pH, remediation, resorcinol, scanning electron microscopy, sorption isotherms, sunflower seed, zinc, Malawi
This study reports on the feasibility of remediation of catechol- and resorcinol-contaminated water using low-cost sunflower seed hull activated carbon (SSHAC). Sunflower seed hull (SSH), an abundant agricultural waste in Malawi, was used as precursor to prepare highly porous activated carbon by physicochemical activation, with zinc chloride (ZnCl₂) as an activating agent. The activated carbon was characterized by FTIR, SEM-EDS, XRD and BET analyses. In this work, pertinent parameters that affect the adsorption efficiency—pH, initial adsorbate concentration, contact time, adsorbent dosage, and solution temperature—were investigated in batch mode. At the same experimental conditions, more catechol was adsorbed than resorcinol may be due to the compound’s affinity towards water and the position of the hydroxyl group on the benzene ring. A maximum equilibrium adsorption of 271 and 250 mg/g was obtained at pH 9.0 and pH 8.0 for catechol and resorcinol, respectively. The adsorption behaviour of both adsorbates (catechol and resorcinol) on SSHAC can be well described by Langmuir isotherm model and pseudo-second-order kinetic model. The value ∆G, ∆S and ∆H indicated spontaneous and endothermic adsorption process. The adsorption process was readily reversible allowing reusability of the adsorbate. This study’s outcome is value addition to this category of wastes for environmental protection.