Ultrasound assisted preparation, characterization, and application of biosorbent for Rhodamine 6G removal from wastewater

Abstract

AbstractNatural adsorbents offer promise for application in environmental protection mainly based on the cost efficiency and biodegradable nature. In the current work, a biosorbent has been synthesized from coconut shell (a common agrochemical waste) in the presence of ultrasound with an objective to improve the microstructure of the carbon coupled with activation using mixture of HNO3 with H2SO4 (7:3 proportion). SEM analysis clearly confirmed that ultrasound induced cavitational effects improved the porous structure of the sample. FTIR and XRD results confirmed the favorable adsorption characteristics for the synthesized activated carbon with no negative changes due to the use of ultrasound. The synthesized adsorbent was used for the removal of a toxic dye, Rhodamine 6G present in effluent at a level of 25 mg L−1. The detailed study into effect of operating parameters elucidated that optimum treatment time for maximum dye removal was 22 min whereas the optimal value of biosorbent loading and pH were 8 gL−1 and 10, respectively. The equilibrium data was fitted into different types of adsorption isotherm models, and Langmuir isotherm model was elucidated as the best fitted model with an adsorption capacity of 90.9 mg g−1. Similarly, the kinetic studies revealed that pseudo second order model fitted better than all the other models. Overall, the efficacy of prepared adsorbent in the presence of ultrasound was effectively demonstrated for the Rhodamine 6G removal from wastewater, also demonstrating the effect of different operating conditions during the adsorption.