PREPARATION, CHARACTERISATION AND APPLICATION OF ALMOND LEAF (Terminalia catappa) DERIVED ADSORBENTS FOR REMOVAL OF BROMOPHENOL BLUE DYE FROM AQUEOUS SOLUTION

Abstract

The resulting effect of indiscriminate discharge of dye solution into the surrounding leads to undesirable mutagenic effects in humans and death of aquatic life in extreme cases. Removal of harmful substance from the effluent of dyeing process and remediation of already contaminated water body is the bane for Environmentalist. A number of methods are available for remediation of dye contaminated water, adsorption has the merit of being a low cost method, a spontaneous process, an effective method for removal of various classes of dye from aqueous solution and has the lowest risk of exposure to the harmful component of dye and dyeing process. Adsorbents were successfully prepared from almond leaf and characterized using Thermogravimetric analysis (TGA), Fourier Transform Infrared (FTIR), Scanning electron microscopy-Energy dispersive Xray (SEM-EDX) and X-ray powder diffraction (XRD). These adsorbents were used for removal of bromophenol blue (BPB) dye from aqueous solution. The optimum quantity of BPB adsorbed at pH 3, dye concentration (100 mg/L), adsorbent dose (0.04 g/25 mL), contact time (60 min) and temperature (301 K) were 92.83, 93.21 and 94.90 for raw Almond Leaf (RAL), Almond Leaf biochar (ALB) and chemically activated Almond Leaf (CAL) respectively. Data obtained from the effect of adsorbent dosage, contact time and temperature were used to determine the adsorption isotherm (Langmuir and Freundlich), kinetics (pseudo first and second Order) and adsorption thermodynamics (Van’t Hoff model) respectively. The monolayer adsorption, Qmax of RAL, ALB and CAL were 365.36, 535.62 and 730.46, respectively. The RL values of RAL ALB and CAL showed that adsorptions process fits the Langmuir isotherm. The experimental data also fits the Freundlich isotherm (0 < 1 𝑛 < 1). However, Freundlich was a better fit due to the higher correlation coefficient value (R2 ). The pseudo second order kinetic better fits the experimental data with a correlation coefficient closer to unity. There is a significant difference between experimental equilibrium dye uptake value qe and the calculated equilibrium dye uptake value (qe(cal)) for pseudo-first order kinetic but the difference was negligible when compared to calculated equilibrium dye uptake value (qe(cal)) for pseudo-second order kinetic. The negative values of ΔG and ΔH values of the thermodynamic study showed that the process is exothermic, spontaneous and feasible for RAL, ALB and CAL. Therefore, the prepared adsorbents are potential alternative to high cost commercial available activated carbon.