Brinjal <i>(Solanum melongena)</i> stalk waste as an effective scavenger for Eriochrome Black-T from water and wastewater: an approach towards waste to best

Abstract

Stalks of brinjal (<i>Solanum melongena</i>), hereinafter SM, have been exercised as an efficient and sustainable adsorbent material for the elimination of Eriochrome Black-T (EBT) from an aqueous solution. The material was characterized by FTIR, FESEM, BET surface area, pH_pzc, and proximate analysis. FTIR spectrum suggests the presence of polyphenolic moieties, responsible for successful dye binding. FESEM images show an unprecedented octopus-like texture containing micropores. The central head transforms the architecture of a flower. The evaluated BET surface area of 10.042 m²/g and pore volume 1.055 × 10^-2cm³/g suggest a porous material. The pH_pzc of the material was evaluated to be 7.05, and under optimized conditions, the maximum adsorption capacity was found 52.631 mg/g at pH 7. The operational parameters were studied concerning contact time (0-90 min), pH (5-11), initial concentration (10-40 mg/L), and interfering ions (PO₄^-3, AsO₄^-3, Hg⁺², Pb⁺²). Adsorption follows Langmuir isotherm best (<i>R</i>² = 0.996), and pseudo-second-order kinetics (<i>R</i>² = 0.991) indicate a monolayer and homogeneous adsorption. 83% regeneration was successful with 0.1(M) sodium hydroxide solution. The material can be reused for up to three cycles with 90% efficiency retention. Analysis of EBT containing industrial effluent indicates that 52.62% of EBT can be removed.