Ultrasonically assisted improved sorption of cationic dye by a cheaper sorbent

Abstract

The goal of this investigation was to evaluate the sorption of malachite green (MG) from aqueous solutions using pumpkin seed peels in the absence of mixing and under low frequency ultrasound. Batch experiments were performedto examine the effect of operating parameters such as sorbent dose (0.05- 0.6 g), initial dye concentration (5– 20 mg/L), initial solution pH (2–8), temperature (25°C–45°C) and ionic strength (0–1 g/L).The following data reveal the quantum of sorption of MG was greatly enhancedunder ultrasound conditions.  Dyestuff sorption when ultrasound is used was significantly increased by increasing the initial sorbent concentration and by reducing the sorbent quantity.The ionic force hinders the sorption of the pollutant.The basic pH was found to be the most advantageous for the sorption of MG.At pH 2, sorption is low due to competition between H⁺ ions and VM molecules to occupy the sorption sites. At this pH, the pumpkin seed surface is positively charged (pH < pH_PZC =4.92).The sorption kinetic data were found to be well-represented bythe pseudo-second-order rate equation, both in the absence and presence of ultrasound (r ≥ 0.996). Analysis of the sorption kinetics results reveals that film and particle diffusion are successful sorption mechanisms. Additionally, the sorptionisotherm data were analyzed by two isotherm models Langmuir and  Freundlich models. Equilibrium data can be well described by the Langmuir model for both methods,, showing maximum monolayer sorption capacity (qm) of 8,9445 and 15,0375 mg/g at21°C, respectively.