Phenol (PHEN) adsorption using hydrogen chloride (HCl) modified barley husk (MBH) was studied, in which the effects of MBH dose (0.5-4 g/L), initial pH (3-11), contact time (10-180 min), and initial PHEN concentration (10-100 mg/L) were investigated. The adsorbent material was prepared via the chemical activation method. The MBH morphological properties with the surface chemistry characteristics were studied through the Brunauer-Emmett-Teller (BET) surface area, scanning electron microscopy (SEM), Energy Dispersive Xray Microanalysis (EDX), Fourier-transform infrared (FTIR), and point of zero charge (pHpzc) analyses. The data was examined using the four common models of isotherm (Freundlich, Langmuir, Dubinin-Radushkevich (D-R), and Temkin). The pseudo-first-order, pseudo-second-order, and the intraparticle diffusion models were also used to examine the data. Thermodynamics parameters: free energy change (ΔGo), enthalpy change (ΔHo) and entropy change (ΔSo) were evaluated. MBH was highly efficient due to its high surface area (176.2 m2/g). Maximum removal of PHEN (93.95%) occurred at pH 3, MBH dose: 3 g/L, PHEN concentration: 10 mg/L, and contact time: 180 min at a constant temperature of 30 ± 2 ºC. The DR isotherm and pseudo-second-order best represented the isotherm and kinetic data, respectively. The values of ΔGo (-0.056, -0.613, -1.431, -2.052, -2.941 and -3.731 kJ/mol), ΔHo (23.88 kJ/mol) and ΔSo (0.087 kJ/mol K) indicate a feasible, spontaneous and endothermic adsorption process. MBH, a low-cost adsorbent can be used effectively to remove PHEN from PHEN-containing water.
