Influence of composite flocculant of PAC and MBFGA1 on residual aluminum species distribution

In general, majority of biomaterials have shown good biosorption capacities towards certain of metal ions. In this work, microbial flocculant GA1 (MBFGA1) compound with PAC was used to control the residual aluminum in flocculation water treatment. The fluorescence spectrophotometry combined with different pretreatment methods was employed to divide the species of aluminum and determine their concentration. The results indicated that non-labile monomeric aluminum was the dominant specie in residual aluminum and addition of MBFGA1 could efficiently eliminate them. Two quadratic polynomial models with the response variables of flocculating rate and labile monomeric aluminum concentration were established by response surface methodology, respectively. The optimal flocculating conditions were MBFGA1 at 109.37 mg/L, PAC at 81.87 mg/L, initial pH at 8.5, time duration of stir 72.5 min and ambient temperature at 24.3 °C. Fourier transform-infrared spectra and environmental scanning electron microscope analysis indicated that MBFGA1 holded a large number of functional groups, which had strong capacity on binding aluminum and reducing its residual level during coagulation–flocculation.

► We investigate the distribution of Al species after using composite flocculation.
► Removing of Al in the species of acid-soluble depends on flocculating efficiency.
► MBFGA1 not only plays the role of flocculant but also biosorbent to eliminate Al.
► MBFGA1 eliminates Al in particular the form of labile monomeric.
► Surface complex and ion exchange are meaningful for reducing Al toxicity.