Physicochemical and statistical modeling of reactive Yellow 145 enhanced adsorption onto pyrrhotite Ash-Based novel (Catechin-PG-Fe)-Complex

Abstract

A novel organometallic complex adsorbent was synthesized owing to a co-precipitation reaction of iron extracted from pyrrhotite ash residues of the mining activities, catechin extract from green tea, and propylene glycol. Hereafter, the adsorbent (catechin-PG-Fe) was characterized by X-ray diffraction, FTIR, SEM, PZC, and N2 adsorption–desorption. Catechin-PG-Fe shows spherical-like iron oxide nanoparticles of 80 nm dispersed on an amorphous surface, while the specific area was revealed to be significant (230.82 m²/g). Catechin-PG-Fe was then tested for adsorption of Reactive Yellow 145 Azo Dye. The uptake capacity was optimized by the central complex design and response surface methodology, where four adsorption parameters have been considered, including pH (1–5), adsorbent dose (0.6–1.4 g/L), dye concentration (20–260 mg/L) and time (50–250 min). Hence, the adsorbent shows an important capacity for Reactive Yellow 145 of 345.41 mg g⁻¹ at optimum conditions of pH = 1, adsorbent dose = 0.6 g/L, dye concentration = 260 mg/L, and a contact time of 200 min. The experimental data are best fitted to the second-order model, while the equilibrium data fit well to the Freundlich model, which reflects multilayer adsorption on the heterogeneous surface. A comparison within intraparticle and Boyd’s diffusion models confirmed that film diffusion is the rate-limiting step.