Synergistic effect of eco-friendly pistachio shell biomass on nano-MnO2 for crystal violet removal: kinetic and equilibrium studies

Pistachio shell powder-supported MnO2 nanostructure-based eco-friendly nanocomposite (nMPP) was prepared via one-pot redox precipitation method and was characterized by FTIR, XRD, SEM, TEM, BET, TGA/DTA, and XPS techniques. SEM and TEM analysis revealed the pseudo-spherical and nanorod morphologies of the synthesized nano-MnO2 and found agglomerated on the pistachio biomass. The nMPP contains nearly 41% Mn as MnO2 (w/w %) dispersed onto the pistachio shell biomass as confirmed from EDX, TGA, and AAS analysis. The nMPP exhibits multi-process crystal violet (CV) removal phenomenon under different pH of aqueous dye solution. Under acidic pH, nMPP caused oxidative degradation of CV by in situ formed OH radicals; while under the neutral pH, CV undergoes monolayer adsorption onto the surface of nMPP as confirmed from Langmuir adsorption isotherm fit with maximum equilibrium adsorption value of 148.7 mg g(-1). The nMPP nanomaterial exhibits a synergistic effect between adsorption efficiencies of pistachio shell biomass and nano-MnO2 for the effective removal of toxic CV dye. The maximum saturation adsorption and rate constant (k(2)) value obtained from the pseudo-second-order kinetic fit model were 119.13 mg.g(-1) and 5.0 x 10(-4) g.mg(-1) min(-1), respectively. [GRAPHICS] .

Automated summary

In this study, a simple method was used to prepare MnO2 nanostructures supported by pistachio shell powder. The nMPP showed multi-process removal of crystal violet (CV) dye under different pH conditions. Under acidic conditions, nMPP caused oxidative degradation of CV through the generation of hydroxyl radicals. Under neutral conditions, CV was adsorbed onto the surface of nMPP in a monolayer manner. The synergistic effect between the adsorption efficiency of pistachio shell biomass and nano-MnO2 enabled the effective removal of toxic CV dye.