Algae based green biocomposites for uranium removal from wastewater: Kinetic, equilibrium and thermodynamic studies

Industrial wastewater contained a large amount of uranium U(VI) generally produced by uranium mining, nuclear electrical generation causes severe damage to the environment. Plant biomass and microbial available in abundant amounts in nature could be used for U(VI) adsorbent. This research represents, the initiation of biocomposites sorbent composed of two algae, Spirogyra (geen algae) and Vaucheria (yellow green algae) utilized in a batch system for U(VI) adsorption. Separation of the U(VI) from the industrial wastewater was analysed with initial pH, biocomposites' dose, contact time, initial temperature, isothermal, and kinetic behaviour. The prepared biocomposites characterization was performed by Fourier transform infrared spectroscopy (FTIR), particle size distribution (PSA), energy dispersive X-ray fluorescence spectroscopy (EDXRF) and pH point zero charges (pHpzc). The separation of U(VI) particles was favourable at pH 2 with 100 mg of adsorbent dose to 50 mg/L U(VI) initial concentration, within only 40 min at 25 °C with adsorption capability of 24.70 mg/g. The removal efficiency of the synthesized biocomposites was measured in terms of dosage 90.82% and pH 92.44%. The obtained values of correlation regression coefficients for used isotherm models show that the sorption process placed well to Langmuir's and Freundlich's models. According to calculated kinetic studies, experimental results fitted very well to the intraparticle diffusion models and pseudo-second-order (phase I). The enthalpy (ΔH°), entropy (ΔS°) and Gibbs free energy (ΔG°) were ascertained as thermodynamic parameters. Thermodynamic data showed that the sorption process onto algae-based biocomposites is spontaneous and exothermic. Moreover, in biosorption process mixture of algae with silica gel enhances the interaction properties with uranium ions. The developed algae-based biocomposites are bi-functionalised cost-effective and feasible adsorbent to eliminate U(VI) from water.