Biosorption of chromium(VI) by spent cyanobacterial biomass from a hydrogen fermentor using Box-Behnken model

The study explores utilization of waste cyanobacterial biomass of Nostoc linckia from a lab-scale hydrogen fermentor for the biosorption of Cr(VI) from aqueous solution. The biomass immobilized in alginate beads was used for removal of the metal in batch mode optimizing the process conditions adopting response surface methodology (RSM). Kinetic studies were done to get useful information on the rate of chromium adsorption onto the cyanobacterial biomass, which was found to follow pseudo second-order model. Four important process parameters including initial metal concentration (10–100 mg/L), pH (2–6), temperature (25–45 °C) and cyanobacterial dose (0.1–2.0 g) were optimized to obtain the best response of Cr(VI) removal using the statistical Box-Behnken design. The response surface data indicated maximum Cr(VI) biosorption at pH 2–4 with different initial concentrations of the metal in the aqueous solution. The biosorbent could remove 80–90% chromium from solutions with initial metal concentration of 10–55 mg/L. Involvement of the surface characteristics of the biomass was studied through its scanning electron micrographs and Fourier transform infrared (FTIR) analysis.

► Biomass waste from a hydrogen bioreactor is reused as biosorbent.
► Cr(VI) biosorption by immobilized biomass is maximized using Box-Behnken model.
► The biosorption efficiency is high at ambient temperatures and low biomass dose.
► Its biosorption capacity at low Cr concentrations is superior to others reported.
► Suggests possible integration of bioenergy production and bioremediation processes.