Removal of heavy metals from electroplating wastewater by Sargassum fusiforme biomass

Algal bioadsorbents can effectively remove the single heavy metal ion in aqueous solution, but the removal mechanism of coexisting multiple metal ions was relatively complicated. In this paper, Sargassum fusiforme biomass, pretreated by NaOH, was used to remove heavy metal ions Cu(II), Zn(II), Cr(VI) and Ni(II) in the electroplating wastewater, and the effects of pH, temperature, contact time and biomass doses on the removal efficiency and its adsorption mechanism were investigated. The results showed that the optimum pH in the removal efficiency of Cu(II), Zn(II) and Ni(II) was among 6–9, while for Cr(VI), it was 2. The removal efficiency increased when biomass doses were elevated from 2 to 4 g/L, but it maintained constant when the biomass doses were higher than 4 g/L. The adsorption equilibrium of Zn(II) and Ni(II) was reached at about 25 min while for Cr (VI) and Cu (II), it was slightly slow. The influence of temperature on adsorption of heavy metal ions was not obvious. Langmuir model can closely describe the adsorption of heavy metal ions, which indicated the absorption was the monolayer adsorption. The maximum adsorption capacity for Cr (VI) and Ni(II) was significantly higher than that for Cu (II) and Zn(II). The adsorption kinetic can be described by the pseudo-second order kinetic model, indicating that the adsorption process was mainly chemical adsorption. Fourier transform infrared spectroscopy analysis of the adsorbent before and after adsorption showed that the bioabsorption of heavy metals was mainly related to carboxyl group. The results suggested that the algal adsorbent could effectively remove the heavy metal ions in electroplating wastewater and exhibit a good application prospect.