Simultaneous ultrasonic-assisted removal of malachite green and methylene blue from aqueous solution by Zr-SBA-15

In this study, simultaneous and competitive removal of methylene blue (MB) and malachite green (MG) dyes was performed by employing nanostructure Zr-SBA-15, once using solid-phase extraction method (SPE) and again using ultrasonic bath, followed by second-order derivative spectrophotometric method in order to resolve the corresponding overlapped spectra. Zr-SBA-15 characterized by FT-IR, XRD, BET, SEM and EDX techniques. Using the proposed procedure, removal of the mentioned dyes was carried out in the minimum time. Moreover, some of the most influential parameters including the initial concentration of MB and MG, dosage of the absorbent, sonication time and pH of the medium were optimized using central composite design (CCD) in response surface methodology (RSM). Desirability scores demonstrated the optimal conditions as follows: sonication time of 4.78 min, adsorbent dosage of 6.66 mg, pH of 7.15 and initial concentrations of 10.21 and 5.48 mg L-1 for MB and MG, respectively. Under optimum conditions, maximum adsorption capacities of 310.88 and 140.61 mg g(-1) were achieved for MB and MG, respectively. Kinetic studies and calculation of relevant equations from kinetic graphs and isotherm exhibited simultaneous adsorption of the desired dyes, followed by pseudo-second order spectrophotometric method and Langmuir isotherm. (C) 2019 Elsevier Ltd. All rights reserved.