Bioprocessing optimization for efficient simultaneous removal of methylene blue and nickel by Gracilaria seaweed biomass

The pollution of water by heavy metal ions and dyes, particularly from industrial effluents, has become a global environmental issue. Therefore, the treatment of wastewater generated from different industrial wastes is essential to restore environmental quality. The efficiency of Gracilaria seaweed biomass as a sustainable biosorbent for simultaneous bioremoval of Ni2+ and methylene blue from aqueous solution was studied. Optimization of the biosorption process parameters was performed using face-centered central composite design (FCCCD). The highest bioremoval percentages of Ni2+ and methylene blue were 97.53% and 94.86%; respectively, obtained under optimum experimental conditions: 6 g/L Gracilaria biomass, initial pH 8, 20 mg/L of methylene blue, 150 mg/L of Ni2+ and 180 min of contact time. Fourier Transform Infrared Spectroscopy (FTIR) spectra demonstrated the presence of methyl, alkynes, amide, phenolic, carbonyl, nitrile and phosphate groups which are important binding sites involved in Ni2+ and methylene blue biosorption process. SEM analysis reveals the appearance of shiny large particles and layers on the biosorbent surface after biosorption that are absent before the biosorption process. In conclusion, it is demonstrated that the Gracilaria seaweed biomass is a promising, biodegradable, ecofriendly, cost-effective and efficient biosorbent for simultaneous bioremoval of Ni2+ and methylene blue from wastewater effluents.