Abstract
In the present work, the Paracentrotus lividus spines (PLS) are proposed as a novel low-cost non-conventional adsorbent for the removal of malachite green (MG) from aqueous phases in the absence and presence of ultrasonic irradiation and by combining simultaneously ultrasound and mechanical agitation. The PLS was characterized by Fourier transform infrared spectroscopy. Batch process was used for adsorption kinetic and equilibrium studies. The effects of diverse parameters such as contact time, initial dye concentration, adsorbent dose, and solution pH on MG adsorption by PLS were investigated. The obtained results indicate that both the rate and amount of MG adsorption were enhanced in the presence of ultrasound. Dye adsorption under ultrasound assistance was improved with the increase of initial dye concentration and with decreasing the adsorbent dose. Basic pH conditions are more propitious for the adsorption of MG. The simultaneous combination of ultrasound and agitation leads to an intensification of adsorption. Adsorption isothermal data could be adequately simulated by the Langmuir model, and then Freundlich and Temkin models. Langmuir simulation indicated that the adsorption capacities of PLS spines were 22.35, 34.45, and 89.72 mg g(-1) for the classical method, the ultrasound-assisted method, and the simultaneous association of ultrasound and stirring, respectively. The kinetic data are very well-described by the pseudo-second-order kinetics model for the classical method, ultrasound, and combining concurrently ultrasonic irradiation and stirring. The combination of ultrasound and agitation for the adsorption process has proven to be interesting for the treatment of wastewater contaminated with malachite green.