Geopolymer fungal cell integration achieved through passive immobilization: a new sustainable candidate to effectively remove toxic lead contamination.

The novel hybrid sorbent (JEONS5), developed with Neurospora cells immobilized on a geopolymer support, is proposed for the removal of toxic Pb2+ ions. The investigation focused on  sorbent characterization and the potential sorbent-pollutant interactions utilizing zeta potential measurements, infrared spectroscopy (FTIR), scanning electron microscopy (SEM) combined with Energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray fluorescence (XRF), and X-ray photoelectron spectroscopy (XPS). During the sorption process, the joint activity of the geopolymer and Neurospora cells was noted. The groups -OH, -NH, C=O, C-N, Si-O, and Al-O were found to have the potential to be efficient. For effective Pb2+ uptake (> 95%) in batch mode, the optimal pH and JEONS5 dosage were determined to be 5.0 and 0.04 g, respectively, using a metal ion concentration of 100 mg L-1. The uptake was very rapid and independent of temperature; equilibrium was reached in approximately 30 min, with more than 75% of the total uptake occurring within the first 5 min. The Langmuir model proved more suitable for the equilibrium data with a qmax of 1.05×10-3 mol g-1 (217.56 mg g-1), even if the pseudo-second-order kinetic model fitted the sorption kinetics well. Breakthrough and exhaustion points were noted at 20 and 350 min. The JEONS5 column's breakthrough curve is fairly well fitted by Chu's simplistic model. Regeneration tests have shown that JEONS5 exhibited sorption and desorption efficiencies exceeding 90% in the first ten cycles, and even at the end of the 20th cycle, it could still demonstrate 50% sorption efficiency. Mechanistic studies indicate that the Pb2+ sorption process proceeds via several concurrent pathways, including surface complexation, ion exchange, and electrostatic interactions. Our findings argue that JEONS5 has enormous potential for treating toxic Pb2+-contaminated aquatic systems.