ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Sustainable removal of reactive black 5 using green-synthesized ZnO–Pupalia lappacea composite: adsorption behaviour, predictive modelling

Olawale S. Dabo, Deborah O. Aderibigbe, Kazeem K. Salam, Mary A. Oladipo, and Abdur-Rahim A. Giwa

Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, P.M.B. 4000, Ogbomoso, Nigeria

E-mail: sdolawale41@pgschool.lautech.edu.ng

Received: 23 March 2026  Accepted: 13 April 2026

Abstract:

Reactive dyes constitute the largest class of dyes used in cotton dyeing, accounting for a significant proportion of global dye consumption and contributing to their widespread occurrence in aquatic environments. In this study, the adsorptive removal of Reactive Black 5 (RB5) onto a green-synthesised ZnO-incorporated acid-modified Pupalia lappacea composite (Z-APL) was investigated. Pupalia lappacea, an underutilised agricultural waste biomass with no prior reported use as an adsorbent precursor, was employed as both a carbon support and a phytochemical source for ZnO nanoparticle synthesis. The effects of solution pH, contact time, initial dye concentration, adsorbent dosage, and temperature were systematically evaluated. Equilibrium behaviour was analysed using five isotherm models including Langmuir, Freundlich, Temkin, Toth, and Dubinin-Raduskevich. The adsorbent was characterised using pH-point-of-zero charge, Fourier Transform Infrared Spectroscopy, Transmission Electron Microscopy, and Scanning Electron Microscopy. Advanced modelling approaches involving Response Surface Methodology (RSM) and Adaptive Neuro-Fuzzy Inference System (ANFIS) were further employed to optimise and predict adsorption performance. The results demonstrated appreciable adsorption efficiency, with a maximum monolayer capacity of 44.63 mg/g. The Temkin isotherm provided the best fit, while the Elovich model best described the adsorption kinetics (R² = 0.978). RSM indicated that the modified cubic model was statistically significant (P < 0.0001), with solution pH, contact time, initial concentration, and dosage as key process variables. Among the tested ANFIS membership functions, the triangular function showed favourable predictive performance based on testing error evaluation. An economic analysis was conducted to assess the practical feasibility of Z-APL, estimating a production cost of ₦1,886.6/g (~$1.35/g) under laboratory-scale conditions. The findings suggest that Z-APL holds potential as a sustainable and cost-effective material for dye remediation in wastewater treatment.

Keywords: Adaptive neuro-fuzzy inference system; Green synthesis; Optimization; Response surface

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04919-x

Chemical Papers 80 (8) 8855–8872 (2026)