Preparation of magnetic microalgae composites for heavy metal ions removal from water

Hexavalent chromium Cr(VI) and divalent Copper Cu(II) ions were heavy metals that were severely toxic to organisms and aquatic ecosystems. Algae is considered as an eco-friendly and cost-effective method for heavy metal ions treatment, but there are still some disadvantages to be improved. Therefore, In this paper, we combine microalgae biomass with ferric oxide magnetic nanoparticles (MNPs) to prepare a more widely applicable adsorbent. Box-Behnken design (BBD) was evaluated for exploring the significant parameters for maximum adsorption in a binary Cr(VI) and Cu(II) solution using our synthesized MNPs@Algae (M@A) adsorbent and constructed a predictability of 88.84 and 95.6 % quadratic regression model, through ANOVA, Pareto Chart of the standardized effects, Three-dimensional surface plot, desirability function to analysis and discussion each factor further. The combined results from UV-Vis, FTIR, TGA, and SQUID measurements confirmed the successful synthesis and accurate properties of the MNPs@Algae composites. The experiment results indicated that when initial pH 6, 5 mg/L Cr(VI), 20 mg/L Cu(II), M@A(3 : 3), dose (1 g/L), and contact time 6 h can achieve the maximum 58 % Cr(VI) and 73.4 % Cu(II) removal efficiency. M@A can eliminate Cr(VI) and Cu(II) from binary solution and separate them from the solution within a few seconds by a permanent magnet as a feasible and efficient absorbent.