Selective/simultaneous batch adsorption of binary textile dyes using amorphous perlite powder: aspects of central composite design optimization and mechanisms

Herein, the selectivity/simultaneously adsorption associated with Congo Red (CR) and Methylene Blue (MB) has been efficiently undertaken via amorphous perlite. Under optimum conditions of 38 min, 96 mg/L and 312 degrees K for the contact time, the dye concentration, and the temperature, respectively, the optimization study using central composite design (CCD) matrix gave rise to high adsorption yields of 82.22 and 96.65% for CR and MB, respectively. Importantly, kinetic and isotherm studies attested that the batch adsorption occurs as intra-diffusional mass transport onto porous material. The obtained thermodynamic parameters are indicative of an endothermic/spontaneous physisorption process. Whereas SEMEDS characterization revealed the superficial adsorption process of both CR and MB onto perlite. In addition, the FTIR analysis suggests that the adsorption process disrupted the short-range compounds order of perlite samples, revealing the marked crystallinity decrease of the adsorbent after adsorption. Finally, application of these optimum conditions tests on real industrial wastewater show that the adsorption was simultaneous at neutral pH and at 312 degrees K, whereas CR and MB can be selectively adsorbed at pH 4 and 9, respectively.

Automated summary

Selective/simultaneous adsorption of Congo Red (CR) and Methylene Blue (MB) has been effectively achieved using amorphous perlite. Optimum conditions of 38 min contact time, 96 mg/L dye concentration, and 312 degrees K temperature resulted in high adsorption yields of 82.22% for CR and 96.65% for MB. The adsorption process was found to occur through intradiffusional mass transport onto the porous material. Thermodynamic parameters indicated an endothermic/spontaneous physisorption process. SEM-EDS characterization revealed the surface adsorption process, while FTIR analysis showed disruption of compound order and decreased crystallinity of the adsorbent after adsorption. Application of these conditions to real industrial wastewater demonstrated simultaneous adsorption at neutral pH and 312 degrees K, with selective adsorption of CR at pH 4 and MB at pH 9.