Study Of The Mechanism Of Trichoderma Koningiopsis In Chromium-containing Wastewater

In this research, an advantage mold identified as Trichoderma koningiopsis was screenedfrom decayed plant roots, and the resistant effects of Cr（III） and Cr（VI） on the mold were studied.By using the powder of Trichoderma koningiopsis as adsorbent, we studied its effect onremoving Cr（VI） in simulated wastewater. In order to research the adsorption mechanism, thefungus surface was characterized by scanning electron microscopy （SEM）, X-ray diffraction（XRD） and infrared spectroscopy （FTIR）.When the concentration of Cr（III） was lower than10mg/L, Cr（III） could stimulate thegrowth of Trichoderma koningiopsis to some extend. While the concentration of Cr（III） wasmore than10mg/L, it could inhibit the growth of Trichoderma koningiopsis. However, Cr（VI）could inhibit the growth of the Trichoderma koningiopsis in low concentrations, and it hadstronger inhibition ability for Trichoderma koningiopsis than Cr（III）. The minimum inhibitoryconcentration（MIC） of Cr（VI） was150mg/L. Transmission electron microscopy（TEM） resultsshowed that the cell was complete before adsorption, the surface of the cell did not find blackparticles. However, after adsorption of Cr（III）, the black particles were seen on the cell wall. Andafter adsorption of Cr（VI）, not only black particles were seen on the cell wall, but the cell wallwas thickened, cell membrane was perforated. These results indicated that Cr（VI） had strongertoxicity than Cr（III） for bacteria. Using6g/L Trichoderma koningiopsis as absorbent to enrichCr（III） and Cr（VI）, the largest adsorption rate of Cr（III） was25mg/L （41.18%） and the largestadsorption rate of Cr（VI） was1mg/L （41.75%）. With the Cr（III） and Cr（VI） concentrationincreased, the toxic effects of Cr（III） and Cr（Ⅵ） on Trichoderma koningiopsis enhanced andenrichment decreased. In addition, the results also showed that during the adsorption process,Trichoderma koningiopsis could be reduced12.2%Cr（VI） into Cr（III）. GSH concentration in thethe blank control group was1.77mg/g, and GSH concentration in the Cr（Ⅵ） stress group ishigher than the control group. When concentration of Cr（Ⅵ） was10mg/L, the GSH conc. in thebacteria reached the maximum of4.16m/g. GSH concentration increased135%compared withthe blank control group.Trichoderma koningiopsis powder was used as absorbent to remove Cr（VI） in simulatedwastewater. The results showed that the ability of the main factors of Trichoderma koningiopsisadsorption of Cr（VI） follows the order: pH> the initial concentration of Cr（VI）> the amount ofadsorbent. The optimum conditions were: the initial concentration of Cr（VI） was2mg/L, thedosage of adsorbent was2.5g/L, pH was4.5, and the adsorption rate of Cr（VI） was80.37%. Under optimal conditions, the adsorption of coexisting ions for Cr（VI） efficiency as follows: theeffects of Cl^-and NO₃^-were not obvious, SO₄^2-could significantly inhibited the adsorption ofCr（VI） and the inhibition dropped by19.64%. Divalent cations showed different effects on theadsorption of Cr（VI）, Cu²⁺could promote the adsorption of Cr（VI）, and adsorption rate increasedby2.13%. Zn²⁺could markedly inhibit the adsorption, the adsorption rate decreased by16.91%.After reused for seven times, the adsorption capacity decreased by2.86mg/g, but the desorptionefficiency was still high.In order to research the adsorption mechanism of Cr（Ⅵ）, the fungus surface wascharacterized by Thermodynamics, scanning electron microscopy（SEM）, X-ray diffraction（XRD）and infrared spectroscopy（FTIR）. The thermodynamic results show that: Trichodermakoningiopsis adsorption of Cr（VI） conformed Langmuir equation, and the nature of theadsorption reaction is a chemical adsorption. The SEM results indicated that: before adsorptionof Cr（Ⅵ）, the sample surface was rough, with many ravines and holes; After adsorption, thesurface of the sample become dense formation. The XRD experimental results showed that: afteradsorption, the energy spectrum showed the Cr spectrum peak, which indicated that the bacteriahad adsorbed Cr. The FTIR experimental results showed the-OH absorption peak and-PO₄3-absorption peak were shifted. In summary, the process of adsorption for Cr（VI） of Trichodermakoningiopsis existed a complexed reaction mechanism.