Dual cross-linked hydrogel microbial reactor: An improved microbial immobilization technology to treat mixed electroplating wastewater

Abstract

In this study, the microbial immobilization technology has been effectively improved and applied to the treatment of mixed electroplating wastewater. The hydrogel beads embedding peanut shell biochar (PBC) and Pseudomonas hibiscicola strain L1 (strain L1) were prepared by polyvinyl alcohol (PVA) and sodium alginate (SA). Response surface methodology (RSM) was used to optimize the preparation of hydrogel beads, and the optimal conditions were as follows: PBC: 3.26 % (w/v), SA: 1.75 % (w/v), PVA: 7.62 % (w/v). The composites showed a significant increase in wastewater treatment capacity compared that without biochar addition. The optimum removal of pollutants in sequencing batch reactor (SBR) was Ni(II): 79.59 %, Cr(VI): 55.30 %, Cu(II): 83.72 %, Zn(II): 87.09 % and ammonia nitrogen: 74.56 %. Scanning electron microscopy (SEM) results showed that the material had a dense reticulated internal structure and produced a large number of microbial metabolic deposits. Fourier transform infrared spectroscopy (FTIR) detected that the material contained various functional groups such as -OH, -CHO, CO, PO₄^3- and C-H; X-ray diffraction (XRD) analysis showed that crystals of Ni₃(PO₄)₂·8 H₂O, CrPO₄, Cr(OH)₃·3 H₂O, CuCO₃, Zn(OH)₂, and Zn₃(PO₄)₂ were formed on the surface of the material. The structure remained intact and still maintained some microbial activity after seven cycles. Therefore, the material prepared has a broad potential in the treatment of mixed electroplating wastewater.