چكيده به لاتين
Polyethylene terephthalate (PET) and high-density polyethylene (HDPE) are among the most abundant synthetic polymer wastes left in the environment and their degradation in environmental conditions similar to dumpsites such as soil surface and depth and in stagnant and current aquatic environments is important. Due to the non-biodegradability of these polymers, methods such as heating and irradiation with ultraviolet light are used to facilitate this process before microbial degradation. In this study, microbial degradation of the two types of polymers pretreated with heat and ultraviolet, with four types of wood-decaying fungi of native species and four types of microbial mixtures in two phases of liquid and / or soil were investigated. This research was carried out in two general stages: the first stage is the separation of suitable microbial mixture and compatibility and biodegradation of polymers in two phases of liquid and soil with auxiliary carbon sources of phenol and / or hexadecane and the second stage is the use of compatible microbes for biodegradation of polymers. During the first stage process, the growth of microorganisms was examined by optical density, colony counting and pH measurements, and at the end, the amount of quantitative and qualitative biodegradation of polymer samples by SEM, FTIR, contact angle measurement and weight loss were evaluated and effective microorganisms were determined based on them. In the second stage, in order to investigate the degree of polymer degradation by compatible microorganisms from the previous stage, two soil and liquid systems (with direct aeration) without the use of auxiliary carbon sources and by doubling the soil depth were examined for 6 months. SEM results confirm the formation of surface decay, cavities and cracks in the surface of polymers and in control samples, the surface remained smooth and unchanged. The formation or removal of new functional groups, including hydroxyls and carbonyls, can be detected in the wavelenumbers around 1700 and 3000cm-1, due to the application of pretreatments and microbial degradation, by FTIR, in contrast to the control samples. Reduction of the contact angle, which indicates surface hydrophilicity, occurred to less than 5° by pretreatments and up to 30° by treatment with various microorganisms. In the first stage, the maximum weight loss of PET and HDPE in the liquid phase with indirect aeration were 60.2 and 37.7%, with direct aeration 41 and 60.5% and in the soil phase 19 and 18.9%, respectively. In the second stage and with adapted microorganisms, the highest degradation rates for polyethylene terephthalate and high-density polyethylene were 58.9% and 68.5% in the liquid phase by type 1 and 2 activated sludge, respectively, and 5.5 and 22.4% in the soil phase by Bituminous soil source microorganisms were obtained respectively. Based on the kinetic studies performed, the logistic model is well adapted to the resulting data. Also, by calculating the maximum intensity of specific growth and comparing it with the rate of weight loss, it was found that there is a direct relationship between the rate of biodegradation and the rate of growth of microorganisms.
