Process optimization of victoria blue dye removal using polypyrrole-encapsulated zirconium oxide: Mechanistic pathway and economic assessment

Abstract

In this study, an organometallic composite, namely a polypyrrole-encapsulated zirconium oxide (ZrO₂/PPy) nanocomposite, was developed and used to eliminate Victoria blue dye (VB) from water system. Specific surface area of the ZrO₂/PPy obtained from BET study was observed to be 61.822 m²/g. Solution pH of 7.0, ZrO₂/PPy nanocomposite dose of 0.8 g/L, sonication period of 40 min and initial VB dye concentration of 50 mg/L were chosen as optimal test parameters, at which 86.23 (±1.15) % of VB dye elimination was observed. The VB dye uptake process follows pseudo-second-order kinetic model and Langmuir isotherm model, with the later providing the maximum VB dye adsorption capacity of ZrO₂/PPy nanocomposite as 238.09 mg/g. Thermodynamics study suggests the spontaneous (ΔG^o< 0) and endothermic (ΔH^o> 0) nature of the adsorption study. Food processing wastewater causes maximum hindrance (∼20 (±0.90) % −25 (±1.03) %) in the VB dye uptake process while the presence of phosphate (PO₄³⁻) ions can create highest interference (∼17 (±0.93) % −19 (±1.08) %) in the VB dye uptake process. At the optimum test parameter values (adsorbent dose: 1.3 g/L, initial VB dye concentration: 20 mg/L, sonication period: 70 min) as suggested by response surface methodology (RSM), maximum VB dye elimination of ∼96 % was observed. Electrostatic attraction, π–π interaction and hydrogen bond formation are amongst the major uptake mechanisms. Regeneration study indicates ∼19 (±1.36) % of decrease in VB dye elimination (%) after fifth cycle of reuse. The lab scale and industrial scale fabrication expense of 1.0 kg of ZrO₂/PPy nanocomposite were obtained as 75.74 and 22.20 USD, respectively. The findings of this study suggest the potential of ZrO₂/PPy nanocomposite as an effective and economically viable adsorbent to eliminate VB dye from wastewater.