The use of raw and modified acacia leaves for adsorptive removal of crystal violet from water

Abstract

Water pollution has grown significantly over the last decades and has now developed as a serious worldwide problem. The main focus of this work is the removal of crystal violet (CV) dye from water using acacia leaves (AL) and their modified form by citric acid (AL@CA) as adsorbents. The surface characterization of these materials was studied using SEM-EDS, FTIR, XRD, TGA/DTA, and zeta potential. The analysis demonstrated that AL@CA exhibited an open, irregular, and amorphous structure decorated with oxygen-containing functionalities. Furthermore, the AL@CA material is thermally stable up to 260 °C. The influence of adsorbent dose, initial dye concentration, temperature, contact time, and pH on the CV dye adsorption performance was studied. The highest CV removal efficiency of 96.4% was obtained at pH ≥ 6. The electrostatic attractions and hydrogen bonds play a pivotal role in boosting CV adsorption. The pseudo-second-order model could very well describe adsorption kinetics. The equilibrium adsorption data followed the Langmuir model. The maximum uptake capacities of AL and AL@CA were 299.70 and 337.83 mg.g−1, respectively. The thermodynamic study displayed that the adsorption is endothermic and spontaneous. The regeneration of spent adsorbent revealed that the AL@CA material can be useful until five reuse times.