Pterospermum acerifolium leaves, PAL a low-cost bio-based adsorbent for the efficient agricultural waste biomass for removal of noxious bromophenol blue

The sustainable management of dye-contaminated water requires treatment materials that are not only effective but also low-cost, reusable, locally available, and environmental friendly. In this study, agricultural waste biomass derived from Pterospermum acerifolium leaves (PAL) was converted into a bio-based adsorbent for the removal of bromophenol blue from aqueous systems. The work emphasizes the valorization of discarded leaf biomass into a beneficial material, offering a circular and resource-efficient approach for wastewater treatment. The PAL adsorbent was characterized using FT-IR, EDX, SEM, pore-size distribution, and point of zero charge measurements, showing an average pore diameter of 13 nm and a PZC value of 5.40. Batch adsorption studies showed that BPB uptake was influenced by contact time, adsorbent dosage, pH, temperature, particle size, and initial dye concentration, with optimized conditions of pH 4, 1 g PAL dosage, 180 min contact time, 25 °C temperature, and 90–125 μm particle size. The Langmuir isotherm model separately described the equilibrium adsorption behavior, with R2 = 0.9907 and a maximum adsorption capacity of 30.486 mg/g. The pseudo-second-order kinetic model separately described the adsorption kinetics, with R2 = 0. 9958. Thermodynamic analysis confirmed that BPB adsorption onto PAL was spontaneous and exothermic, with reduced randomness at the solid solution interface. Importantly, PAL maintained reusable adsorption capability over five consecutive adsorptions desorption cycles demonstrating its practical relevance beyond synthetic dye solutions. Overall, this study highlights untreated PAL biomass as a sustainable, accessible, and reusable adsorbent for dye-bearing wastewater treatment contributing to agricultural waste valorization and circular environmental management.