Treatment Of Phenol And Chromium From Wastewater By Modified Montmorillonite And Immobilized Microorganism

Heavy metals and organic compound entensively coexist in electroplating, tannery, textile manufacturing industries and so on. The additive effects between the two pollutants make the composition of the wastewater become more complicated and increase the difficulty of polluted wastewater treatment. The co-contamination poses severe threats to the environment when they encountered together in the surroundings such as rivers, soil and so on. Thus, it is a great challenge to remove the two pollutants simultaneously.In this paper, adsorption-biodegradation process was used to remove the co-contamination of phenol and Cr(VI). Cross-linked chitosan/Al13-pillared montmorillonite was used to adsorb Cr(VI). The phenol-degrading bacteria strain, which was isolated from the activated sludge, was used to degrade phenol in the presence of Cr(VI). Immobilization of microorganism was applied to degrade phenol and reduce the concentration of Cr(VI) at the same time. In conclusion, an idea for the treatment of both heavy metals and phenolic compounds was proposed.Cross-linked chitosan/Al13-pillared montmorillonite was synthesized by modifying the montmorillonite through organic-inorganic methods to remove Cr(VI). The maximum removal efficiency(the cross-linked chitosan-to-clay ratio 0.6:1, 25℃, initial concentration 100mg/L, contact time 4 h, pH 5.40, adsorbent 25g/L) was 95.0%. The adsorption process followed the Langmiur isotherm equation and the dynamic behavior of the process is in agreement with the pseudo-second order equation, In addition, the adsorption was also a spontaneous and endothermic process with increased entropy.Bacillus sp. FG-01 could degrade phenol in the presence of Cr(VI). The degradation was an aerobic process and the degradation rate of phenol was 99% in optimal conditions(35℃, pH 6.24, 3%of inoculation amount(v/v), initial phenol concentration 50mg/L), the bacillus has a certain tolerance to Cr(VI). Comparison of the tolerance to Cr(VI) and Zn(Ⅱ) was investigated. For the same concentration(5 mg/L) of Cr(VI) and Zn( Ⅱ), the phenol-derading rate of 99% is achieved at 152 h for to Cr(VI), 33 h Zn(Ⅱ), respectively. The inhibition effect of Cr(VI) to the bacteria is higher than that of Zn(Ⅱ). The kinetic of phenol biodegradation could well accord with the zero order equation in the presence of heavy metals with low concentration(1~4 mg/L Cr(VI)、5~25 mg/L Zn(Ⅱ)). The UV-vis results showed that the degradation of phenol was inhibited to some extent by Cr(VI), but the degradation mechanism can not be changed.Bacillus sp. FG-01 immobilized into chitosan beeds(BICB) was applied to remove phenol and Cr(VI). When the initial concentration of phenol was 50mg/L, Cr(VI) was 1mg/L, dosage was 0.42 g/mL, the removal efficiency of both by BICB was 99% and 60%, respectively. The removal performances of BICB were compared with that of free cells, and the results showed that the removal ability and the tolerance to Cr(VI) of BICB are much higher than free cells. The removal rate was up to 96.12% after the seventh cycles. The removal rate of phenol was even up to 93.10% enven if BICB was stored at 4℃ for 42 days.