Removal of reactive black 5 by activated carbon from pineapple leaves via ultrasonic assisted adsorption

Abstract

Adsorption is a prominent process for the treatment of dye from textile wastewater due to its simplicity. However, usage of commercial activated carbon in adsorption is costly and inconvenient for regeneration process. Hence, there is a need to shift towards new adsorbents that are low cost and highly efficient. Therefore, this study focused on the synthesis of new activated carbon with pineapple leaves as a precursor for the removal of reactive black 5 (RB5) dye. Chemical activation method was employed to tailor the internal porous structure and surface area of the adsorbent. Treatment with sodium hydroxide had achieved high removal compared to other activating agents. The effect of four preparation variables: impregnation ratio, impregnation time, carbonization temperature and carbonization time on RB5 uptake from aqueous solution were investigated. Based on the Box-Behnken design, a quadratic model was developed to correlate the preparation variables to the RB5 uptake. The significant factor in each experimental design response was identified from the analysis of variances. The optimum pineapple leaves activated carbon (PLAC) was obtained using an impregnation ratio of 3.75, carbonization temperature of 517°C and carbonization time of 1 hour 22 minutes. Then, the synthesized PLAC was characterized using field emission electron microscopy, Fourier transform infrared spectroscopy, Brunauer Emmett Teller surface area, energy dispersive Xray, and point of zero charge. A batch experiment was conducted under ultrasoundassisted adsorption. The results obtained were excellent with almost up to 100% RB5 removal under the following conditions; 35 min of contact time, 0.1 g of adsorbent, and 0.05 g/L of initial RB5 concentration, pH 5 and at 30 °C. Kinetic, isotherm and thermodynamics evaluation were also performed for the adsorption data. The adsorption data fitted well to the pseudo-first-order model with the influence of intraparticle diffusion. For the isotherm, the data best fitted to the Langmuir model with the maximum adsorption capacity of 103 mg/g. A thermodynamics analysis showed that the adsorption was exothermic and spontaneous. The PLAC can be reused five times with the percentage removal above 60%.