微生物对切削液稳定性的影响

Influence of Microbial on Stability of Metalworking Fluids

将现场采集的切削废液扩培至不含抑菌剂的切削液中,通过对切削液中微生物多样性分析及微生物对切削液的降解作用研究,探讨微生物对切削液稳定性的影响,发现具有假单胞菌属、水生丛毛菌属、红平红球菌等优势菌种会严重降解切削液中的有机物质,使pH值和总有机碳含量下降,无机碳升高;微生物使切削液劣化严重,影响其稳定性,浊度在前两周增大,平均液滴粒径分布增大了7倍,最大粒径尺寸增大了20倍,液滴之间发生了聚合现象,出现了游离态油相物质。通过DLVO理论与乳液液滴流体动力模型分析,得出微生物的失稳影响机制为:微生物对有效成分的降解改变了切削液的介电常数,赋予乳液液滴大于聚合势垒的活化能,从而形成乳液之间的聚合,降低了切削液的稳定性。

The microbial influence of stability in metalworking fluid(MWF)was studied by adding the waste metalworking fluid into the MWF without biocides,and the microbial diversity in cutting fluid and the degradation of cutting fluid by microorganism was analyzed.Results show that dominant bacteria are identified as Pseudomonas sp.,Comamonas sp.,Rhodococcus erythropolis.Severe biodegradation are found in the MWF during 12 weeks of enrichment.Total organic carbon(TOC),pH of the MWF present a declining tendency under the microbial influence while inorganic carbon(IC)exhibits an increasing tendency.The microbially influenced destabilization of emulsion occurs during the first two weeks.Turbidity is increased dramatically and medium and maximum of droplet size distribution are 7 and 20 folds greater than in fresh MWF.The coalescence in droplets and free state oil is found in the MWF containing microorganisms.The mechanism of microbial destabilization in the MWF was discussed by the DLVO theory and hydrodynamic model.It can be informed that dielectric constant is increased by microbial degradation of organic substance,in which endows more activation energy to emulsion particles.The coalescence of particles occurs when the activation energy of particles crosses over barrier potential.