Study On Adsorption Of Phthalates On P(HB-HV) Porous Adsorbent

Phthalate Esters?PAEs?are one of the endocrine disrupting chemicals.It has a potential harm for human health duo to its mutagenicity effect,teratogenicity effect and carcinogenicity effect.Along with the improvement and development of industrial technology,lots of PAEs were used in the plastic products and lead to a global social problem because its spreading in the environment.As some hydrophobic organic contaminants can be bio accumulated in fats of organisms,the porous adsorbents prepared by Poly?hydroxybutyrate/hydroxyvalerate??P?HB-HV??,which is synthetized in the cells of the microorganisms,were used to study of the remove PAEs from wastewater.In this paper,typical PAEs-Dimethyl Phthalate?DMP?and Diethyl Phthalate?DEP?were chosen as pollutant samples to study the adsorption properties of porous adsorbent P?HB-HV?which was used to adsorb the PAEs in water.The P?HB-HV?porous adsorbent was characterized isothermally by N₂ adsorption to analyze the BET surface area,pore volume and pore size distribution of the adsorbent.The charges distribution characteristics in adsorbent surface were measured by pH-drift experiment.The effects of the P?HB-HV?porous adsorbent in different adsorption conditions,such as contact time,adsorbent dosage,PAEs initial concentration,pH and temperature,on the adsorption of PAEs was researched by static adsorption experiments,respectively.The static experiment data were analyzed by various adsorption kinetics models?the pseudo-first-order and the pseudo-second-order and the intra-particle diffusion model?and adsorption isotherm models?Langmuir and Freundlich model?.And several important thermodynamic parameters such as,?G^O,?H^O and?S^O were studied to investigate the thermodynamic behavior.In addition,the adsorption mechanism of DEP in a fixed bed of P?HB-HV?porous adsorbent was studied and the impacts of feed concentration and feed flow rate on the DEP adsorption breakthrough curve was discussed.An adsorption breakthrough model of DEP was established based on the Freundlich isotherm equation and the constant-pattern wave approach theory,which was used to predicted the adsorption breakthrough curve.The main results are concluded as follows.?1?the BET surface area,pore volume and pore size distribution of P?HB-HV?porous adsorbent was determined by N₂ adsorption and desorption constant temperature characterization and the results indicate that the P?HB-HV?porous adsorbent was mainly composed of mesoporous and has higher surface area and abundant pore size distribution.The zero charge point in adsorption surface is 7.71 and was determined by the pH-shift experiment.?2?The impact of different adsorption condition on the P?HB-HV?porous adsorbent was observed by static adsorption experiment.The study shown that equilibration time when P?HB-HV?porous adsorbent adsorbed DMP and DEP is approximately 240 min.The adsorption capacity of DMP and DEP on the P?HB-HV?porous adsorbent magnifies and the removal efficiency of DMP and DEP decreases gradually with the increase of the initial concentration.The adsorption capacity of DMP and DEP on the P?HB-HV?porous adsorbent enlarges with the increase of the contact time and adsorption doses,respectively,whereas decreases with an increase in temperature and pH value.?3?The study of the adsorption constant temperature equation shown that the Freundlich mode can well describe the DMP and DEP adsorption process of the P?HB-HV?porous adsorbent.The research on the adsorption dynamics illustrated that the pseudo-second order model can better describe the process that the P?HB-HV?adsorb the DMP and DEP.The intraparticle diffusion kinetic model showed that the internal diffusion isn't the only one adsorption rate-controlling step.The thermodynamic research indicated that DMP and DEP adsorption on the P?HB-HV?porous adsorbent is spontaneous and exothermic reaction process and an increase in temperature was unfavorable for DMP and DEP adsorption.?4?The adsorption breakthrough curve of DEP in the fixed bed of P?HB-HV?porous adsorbent measured with different feed flow rates and feed concentrations illustrate the higher feed rate and feed concentration of DEP are,the earlier the breakthrough time become and the little higher the slope of the breakthrough curve also increase.the predicted breakthrough curves fit well with the experimental one,indicating that the proposed model for fixed bed based on the Freundlich isotherm equation and the constant-pattern is suitable for describing the adsorption process of DEP in fixed bed.