Bioremoval of heavy metals from aqueous solution using dead biomass of indigenous fungi derived from fertilizer industry effluents: isotherm models evaluation and batch optimization

The present work investigated the utilization of dead biomass of the highly multi-heavy metals tolerant indigenous fungal strain NRCA8 isolated from the mycobiome of fertilizer industry effluents that containing multiple heavy metal ions at high levels to remove Pb(2+), Ni(2+), Zn(2+), and Mn(2+) as multiple solutes from multi-metals aqueous solutions for the first time. Based on morphotype, lipotype and genotype characteristics, NRCA8 was identified as Cladosporium sp. NRCA8. The optimal conditions for the bioremoval procedure in the batch system were pH 5.5 for maximum removal (91.30%, 43.25%, and 41.50%) of Pb(2+), Zn(2+) and Mn(2+) but pH 6.0 supported the maximum bioremoval and uptake of Ni(2+) (51.60% and 2.42 mg/g) by NRCA8 dead biomass from the multi-metals aqueous solution, respectively. The 30 min run time supported the highest removal efficiency and uptake capacity of all heavy metals under study. Moreover, the equilibrium between the sorbent NRCA8 fungal biomass and sorbates Ni(2+), Pb(2+) and Zn(2+) was attained after increasing the dead biomass dose to 5.0 g/L. Dead NRCA8 biomass was described by scanning electron microscopy, energy-dispersive X-ray spectroscopy and Fourier transform infrared spectrometer before and after biosorption of Pb(2+), Ni(2+), Zn(2+) and Mn(2+) under multiple metals system. The Langmuir, Freundlich and Dubinin-Kaganer-Radushkevich isotherms were applied to characterize the adsorption equilibrium between Pb(2+), Ni(2+), Mn(2+) and Zn(2+) and the adsorbent NRCA8. By comparing the obtained coefficient of regression (R(2)) by Freundlich (0.997, 0.723, 0.999, and 0.917), Langmiur (0.974, 0.999, 0.974, and 0.911) and Dubinin-Radushkevich (0.9995, 0.756, 0.9996 and 0.900) isotherms values for Pb(2+), Zn(2+), Ni(2+) and Mn(2+) adsorption, respectively, it was found that the isotherms are proper in their own merits in characterization the possible of NRCA8 for removal of Pb(2+), Zn(2+), Ni(2+) and Mn(2+). DKR isotherm is the best for Pb(2+) and Ni(2+) (0.9995 and 0.9996) while Langmiur isotherm giving a good fit to the Zn(2+) sorption (0.9990) as well as Freundlich isotherm giving a good fit to the Mn(2+) sorption (0.9170). The efficiencies of Cladosporium sp. NRCA8 dead biomass for bioremoval of heavy metals from real wastewater under the optimized conditions were Pb(2+), Ag(+), Mn(2+), Zn(2+) and Al(3+) ˃ Ni(2+) ˃ Cr(6+) ˃ Co(2+) ˃ Fe(3+) ˃ Cu(2+) ˃ Cd(2+). Dead NRCA8 biomass showed efficient ability to adsorb and reduce harmful components in the industrial effluents to a level acceptable for discharge into the environment.