| Humic acid, which is a complex of the organic polymer class with a carboxyl and hydroxyl functional groups, is widely distributed in the soil and water. It is a profound influence on the transformation of organic and biological activity in the environment. Ophthalmic acid esters (PAEs), also known as phthalates, are the generally colorless, oily viscous liquid. It increases the ductility and softness of the polymer material, and therefore it is often used as the plasticizer of the polyvinyl chloride (PVC), cellulose resins, natural rubber and synthetic rubber. It easily transfers to the atmosphere, water, soil, and the organism. PAEs have their teratogenicity, mutagenicity and carcinogenicity, so they become a kind of priority control of persistent organic pollutants.The environmental protection agency of United States focused on pollutant list contains six PAEs:DMP, DEP, DBP, DOP, and BBPand DEHP.PEAs pollution already appeared the trend of globalization. They are widely found in the water, atmosphere, soil and sediments, as well as important organic pollutants studied by the environmental scientists. Studies show that, surface water generally contains varying degrees of PEAs. PAEs were detected in source water and Sediments in many countries. China’s water environment by PEAs pollution situation is very serious, and many water systems detect varying degrees of PAEs pollution. In this paper, the study of adsorption-desorption of dibutyl phthalate on humic acid resolves that how the humic acid adsorbent the dibutyl phthalate (DBP) in the fastest rate.The study is in order to provide the basic information for environmental protection. The article chooses DBP as the research object, which is a high content in the soil and water in china. At the same time, it is also is the priority control of PAEs (typical organic pollutants) both in China and the Unites-States. The Solid phase extraction-high performance liquid chromatography and the infrared spectroscopy is used to study the adsorption kinetic characteristics of humic acid on DBP, the adsorption and desorption characteristics, the effect of pH, temperature and other environmental conditions on the adsorption, desorption,and the presence of humic acid under the conditions of DBP degradation law. It has important theory meaning of revealing adsorption of DBP on the degradation of humic substances, circulation, bioaccumulation and toxic transformation rule. The results are as follows:1. According to the study of isothermal adsorption kinetic characteristics of the humic acid on DBP under the condition that the initial concentration of DBP is4.00μg/ml at25℃, it indicates that when the adsorption time exceeds24h, the adsorption is basically leveled out and the adsorption kinetics lives up to Elovich equation, two-constant equation and Lagergren second order kinetic equation, the last of which refers to the optimal equation that describes the reaction kinetics; The internal diffusion model indicates the reaction might be under the joint control of pre diffusion and internal diffusion.2. According to the DBP isothermal adsorption and desorption test of humic acid, it indicates the adsorption capacity of DBP increases according to the increase of DBP’s equilibrium concentration, thus the relationship between adsorbent and adsorbate could be manifested by Langmuir equation.3. The thermodynamic test indicates that the temperature imposes obvious influences on adsorption and desorption. The adsorption quantity and adsorption rate of DBP, at35℃, is clearly lower than that at25℃while the desorption rate at35℃is clearly higher than that at25℃. The thermodynamic parameter of the adsorption process fully confirms this conclusion. It thus shows that the adsorption mechanism of humic acid in DBP is a spontaneous and exothermal reaction under the joint control of surface physical and chemical adsorption but the physical adsorption prevails.4. The functional group, corresponded by the main adsorption peak of DBP composite’s infrared spectrum arising from the reaction of the humic acid with the DBP of different concentrations it absorbs, mainly originates from various hydroxide radicals and carboxyl in the humic acid molecules and various C=O in humic acid and DBP molecule, derivatives of benzene, methyl and C-O, etc. However, the infrared spectrum analysis result indicates that the adsorption mechanism of humic acid in DBP mainly refers to the hydrogen bond interactions among molecules of humic acid and DBP. 6. Through study on the test of UV radiation wavelength’s degrading of DBP, it is found that the degradation rate under the254nm short wave ultraviolet is higher than that under35nm; the control test indicates that degradation rate of DBP’s concentration will enlarge according to the increase of the degradation time under the254nm short wavelength ultraviolet radiation, thus the degradation characteristic lives up to the secondary kinetic characteristic; the degradation characteristic of DBP under the condition that there exists the exogenous humic acid also lives up the secondary kinetic equation. Through comparison, under254nm short wavelength UV radiation and under the condition that there exists the exogenous humic acid, the degradation rate of the organic pollutant’s DBP is lower than a lot than that in the control group. The degradation secondary kinetic equation speed constant under the condition of the control test and added humic acid can prove the degradation of DBP is weakened by the existence of the humic acid. |
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