REMOVAL OF METHYLENE BLUE FROM SYNTHESIZED WASTEWATER USING SURFACE MODIFIED IKPOBIA CLAY

Synthetic dyes like methylene blue are toxic, persistent, and non-biodegradable, hence releasing wastewater contaminated with dyes into the environment presents significant ecological and health risks. Thus, creating inexpensive and environmentally friendly adsorbents from locally accessible materials has emerged as a viable wastewater treatment approach. This study evaluated the surface modification of Ikpobia clay for the elimination of synthesized methylene blue from aqueous solution. The clay samples were modified by calcination using a furnace at an optimum temperature of 300oC and also by acid activation using oxalic acid impregnation in which the clay to acid ratio was 1:1. The refined, calcined and acid modified clay samples (RC, CC and AC) were characterized by pH, Fourier transform infrared (FTIR), x-ray diffraction (XRD), scanning electron microscope/electron dispersive x-ray (SEM/EDX), Brunauer-Emmett-Teller (BET) surface area and thermal gravimetric/differential thermal analysis (TGA/DTA), and methylene blue adsorption in batch mode was also studied at varying initial concentrations, solution pH, adsorbent dosage, contact time and temperature. The pH was more acidic in AC (5.15) and slightly acidic in RC and CC (6.84 and 6.56). The FTIR and XRD peaks suggested the presence of O‒H, Si‒O or Al‒O, Al‒OH and Si‒O‒Al or Si‒O‒Si which were characteristics of kaolinite, illite, siderite and quartz minerals. The BET surface area increased from 235.50 m2/g for RC to 313.70 m2/g for AC, but reduced to 213.80 m2/g for CC. The maximum adsorption capacity,Q_max, of methylene blue was 40.301 mg/g, 33.988 mg/g and 37.486 mg/g for RC, CC and AC, respectively. The pseudo-second-order model best described the adsorption kinetic data due to its least sum of square error (SSE), highest regression coefficient (R2 →1) and better adapted calculated adsorption capacity (q_(t,cal)) to the experimental data(q_(t,exp)). The thermodynamics study suggested adsorption feasibility and spontaneity of Ikpobia clay. RC exhibited the best performance. The adsorption mechanism suggested a monolayer removal of methylene blue onto a heterogeneous surface of RC and the possibility of strong chemical bonding due to the predominance of negatively charged oxygen functional groups of carbonyl (C=O) and hydroxyl (O–H), ion exchange and electrostatic attraction. This study has placed Ikpobia clay as a low cost alternative and credible candidate for effective cationic pollutants removal from wastewater