Physicochemical Investigations on the Removal of Fe(III) Metal Ions from Aqueous Media through Biosorption by Using Thermo-Chemically Modified Oyster Mushroom-Based Adsorbents

Herein, the cost-effective utilization of biosorption for toxic pollutant removal was investigated, with a specific emphasis on enhancing mushroom-based biosorbents for the decontamination of heavy metals-polluted aqueous environments. Firstly, Oyster mushrooms (Pleurotus ostreatus) collected from Bajaur, Khyber Pakhtunkhwa, Pakistan, underwent thorough cleaning, followed by air-drying for 2–3 weeks to produce a fine powder. The obtained powder was subjected to thermal modification through heating at 400°C/1 h, and a portion of it was additionally modified using potassium hydroxide (KOH). This process resulted in three distinct materials: untreated dried mushroom (AM), thermally modified mushroom (TMM), and chemically modified mushroom (CMM), and their chemical compositions were assessed using Fourier Transform Infrared (FTIR) spectroscopy. Subsequently, the resulting materials were employed as bioadsorbents for the elimination of toxic Fe(III) ions from aqueous media. Various experimental variables, including solution pH, temperature, contact time, pollutant concentration, and adsorbent amount were varied to investigate their impact on adsorption. Analysis using an atomic absorption spectrophotometer (AAS) demonstrated exceptional Fe(III) removal capacities of mushrooms, achieving a removal extent of 29.99 mg/g at 303 K, pH 6.0, and an adsorbent dosage of 0.1 g/L, resulting in a remarkable 99.97% removal efficiency. The type of adsorbent significantly affected the extent of adsorption. Furthermore, thermodynamic analysis revealed that adsorption was spontaneous and exothermic. The adsorption data were evaluated using Langmuir, Freundlich, and Temkin isotherms, with the pseudo-second-order reaction kinetics providing the best fit, suggesting that chemisorption predominates the surface adsorption of Fe(III). This study highlights the potential of mushroom-based biosorbents as eco-friendly and effective materials for purifying water contaminated with toxic pollutants.