Study On Phthalic Acid Esters In Xi'An Surface Water And Its Separation Characteristics Of Nanofiltration Membrane

Phthalic acid esters (PAEs) are a series of poisonous and deleterious chemical compounds in environment. It may affect human and animal on their normal endocrines, cause reproductive, developmental and behavioral disorder through eating and touching. In this paper, four kinds of phthalic acid esters, such as diethyl phthalate (DEP), dibutyl phthalate (DBP), dicyclohexyl phthalate (DCHP) and di (2-ethylhexyl) phthalate (DEHP) were choosed as the research object. The method of solid-phase extraction-gas chromatography-mass Spectrometry (SPE-GC-MS) was used to analyse PAEs in this study. Analysis of some phthalic acid esters in Xi'An surface water and its nanofiltration membrane's separation characteristics of some phthalic acid esters have been studied in this paper.(1) In different season, through monitoring and analysis PAEs in Xi'An surface water, pollution of PAEs in surface water were found. The concentration of PAEs was DEP (0.10～0.57μg/L) , DBP(0.18～12.00μg/L), DEHP(0.04～0.87μg/L) ,DCHP(0～0.11μg/L) .And the concentration of DBP was above the nation surface water standard; concentration of DEP and DEHP were greater than those reported abroad. The concentration of PAEs was infuenced by the water quantity and quality in different time. The PAEs concentration Change of Wei river were those: dry period is higher than general period, and general period is higher than flood period; the worse the water quality is, the higher the concentration is.(2) Research indicated that effect of conventional treatment technology was not good for removal pollution of PAEs, and 2.03μg/L PAEs still existed in treated water. Through material invariableness calculation found that removal pollution of PAEs mainly depended on chlorine oxidation and the effect of coagulation sedimentation-filtration was only separation. For filter backwash water recovery causing accumulation of PAEs, treated water carried of about 77% PAEs and sludge carried of about 11% PAEs. The safety problem of filter backwash water recovery should be considered. The improvement of conventional treatment technology effect to removal pollution of PAEs was imperative. Through simulation experiment, the quantity of PAEs in water increased by adding flocculant with PAEs.(3) Experimental results indicated that trace EDCs in water could be rejected very effectively by nanofiltration, the average rejection efficiency was above 90%; the effect of BDXN-90 membrane was better than BDXN-70 membrane.The main factors that affect membrane property were operational conditions (time, pressure) and raw water (pH, ionic strength and humic acid). With the prolonging of reaction time, the membrane flux was almost same, but the rejection of PAEs was higher at first and then decreased; with the rise of pressure, the membrane flux increased and the rejection wasn't change. With the rise of pH, the membrane flux increased and the rejection of PAEs was decreased by charge neutralization and electric double layer compression; With the rise of ionic strength, the membrane flux declined and the rejection of PAEs increased by compression of electric double layer; In same ionic strength, the membrane flux of CaCl₂ was smaller than KCl, rejection of PAEs was higher. When humic acid was in water, concurrent action of humic acid and metal ions cause membrane fouled, pore filled, membrane flux declined and rejection increased. The more the ionic strength is, the moer the effect is.(4) The regularities of nanofiltration separation PAEs in both humic acid water and surface source water are similar. This result shows that: Concurrent action of humic acid and Ca²⁺ cause membrane fouled, pore filled, membrane flux declined and rejection increased.(5) Separated trace PAEs of surface water by BDXN-90 membrane in long time was studied. The result shows that: the membrane flux was 10L/m².h stably, and the rejection of PAEs was above 98%.