Removal of anionic dye from aqueous solution using magnetic sodium alginate beads

Magnetic sodium alginate beads (MSAB) was synthesized and used for the adsorption of hazardous azo pyrazole dye (AP). The effect of different variables in the batch method as a function of solution pH, contact time, concentration of adsorbate, adsorbent dosage and temperature were investigated and optimal experimental conditions were ascertain. Surface modification of MSAB using scanning electron microscopy (SEM) was obtained. More than 80 % removal efficiency was obtained within 70 min. at adsorbent dose of 0.02 g for initial dye concentration of 4x10^-5–1x10^-3 M at pH 2. The Brunauer-Emmett-Teller (BET) surface area and Barrett-Joyner-Halenda (BJH) pore volume were calculated and found to be 111.061 m^2g^-1 and 0.148 cm^3g^-1, respectively. The point of zero charge (pHPZC) of MCAB was determined and found to be 7.5. The molecular and electronic structure of the investigated dye was also studied using quantum chemical calculations. The adsorption equilibrium showed that the Langmuir equation represented best fit of the experimental data than others. The adsorption kinetics was found to follow pseudo-second-order kinetic model, suggesting a chemisorption process. Adsorption thermodynamics study suggested that the adsorption reactions were spontaneous, endothermic and thermodynamically favorable.