Please use this identifier to cite or link to this item: http://prr.hec.gov.pk/jspui/handle/123456789/13216
Title: Use of new materials for the removal of phthalates by solid phase extraction
Authors: Qureshi, Umair Ahmed
Keywords: Chemistry
Issue Date: 2015
Publisher: University of Sindh, Jamshoro.
Abstract: Phthalates (PAEs) are chemical compounds that are most widely used by plastic manufacturing industries. The function of PAEs in plastics is to confer elasticity and flexibility in the polymer structure. PAEs are considered most toxic chemicals which cause carcinoma and other carcinogenic diseases. They are also considered endocrine disrupting chemicals (EDCs) which affect male reproductive systems and cause birth defects in infants. PAEs have been widely used in different commercial products such as packed foods, cosmetics, baby nipples, baby toys and blood transfusion bags. The final destiny of PAEs is the water. PAEs may also be found in bottled water; prolonged exposure to exceeding heat from environment may cause discharge of PAEs from plastic into water. PAEs are also commonly found in industrial water from polymer industries. Due to the above facts, there is an urgent requirement for the attenuation of toxic PAEs from environmental water bodies. Different techniques are available for PAEs removal but the target of the present thesis is “removal of PAEs by adsorption technique” due to its simplicity and low cost materials for removal purpose. The present thesis is divided into the study of five different types of adsorbents for different PAEs removal. Part 1 of the current thesis deals with the study of dibutyl phthalate (DBP) removal by newly prepared adsorbents including room temperature ionic liquid (RTIL) coated XAD-4 resin (RTIL-XAD-4). The coating of XAD-4 by RTIL was characterized by FTIR. The adsorption process was optimized by investigating the influence of pH, time, concentration and temperature. The suitable parameters achieved were pH 6, time 30 min, temperature 298 K (room temperature), and a wide range of concentration for DBP removal. Kinetics of adsorption was pseudo second order, while equilibrium experimental data fitted both Freundlich and D-R isotherms with the adsorption capacity 83.1 mg/g from Freundlich and 30.7 mg/g from D-R isotherms. Thermodynamic adsorption was endothermic in nature and spontaneous in nature. The application of RTIL-XAD-4 on DBP removal showed satisfactory performance. Part 2 of the present study deals with utilization of Pine nut shell based carbon by simple carbonization of the precursor. In this study, adsorption performance of four different types of PAEs (namely DMP, DEP, DAP and DBP) were studied. Different characterization techniques such as point of zero electric charge (PZC), FTIR, SEM, BET and elemental analysis showed successful formation of carbon adsorbent designated as PNSC. Different experimental parameters such as time, pH, dosage, concentration and temperature were optimized and the following parameters were found suitable for maximum PAEs removal i.e., time 2 hrs, pH 2, dosage 0.4 g, concentration 2 mg/L each PAEs. Kinetics of adsorption were pseudo second order type. The adsorption efficiency was increased with increasing alkyl chain with the following order DMP>DEP>DAP>DBP. Equilibrium experimental data were best fitted with Langmuir isotherm with increasing adsorption capacities from DMP to DBP (2.48-5.65 mg/g). Thermodynamically the adsorption was exothermic in nature. Part 3 of the thesis is based on the application of low cost material namely Cantaloupe peel a sweet fruit mostly found in Pakistan during summer. DEP and DBP were selected as model pollutants for investigating adsorption performance of peels. FTIR characterization revealed that the peels were rich in polysaccharides and some proteinaceous matter which were the binding sites in peels for DEP and DBP uptake. Different experimental parameters were investigated and the optimum parameters obtained were pH 6.5 (normal working pH), time 25 min, dose of peels 0.1 g, initial concentration 7 mg/L and temperature 298 K. The kinetics of adsorption were pseudo second order while equilibrium study revealed that adsorption follows Freundlich isotherm well with maximum adsorption capacity for DEP 0.151 mg/g and for DBP 0.351 mg/g. Thermodynamically, adsorption was exothermic in nature. Presence of humic acid as a model of natural organic matter (NOM) had bad impact on adsorption performance of cantaloupe peels. As compared to DBP removal, DEP removal performance was badly affected with rise in humic acid concentration. The regeneration studies of cantaloupe peels showed that these peels are usable only once. Part 4 of the current thesis includes fabrication of seven different types of hydrogels based on polyvinyl alcohol, chitosan and Fe3O4 magnetic particles including non magnetic hydrogel. The six other hydrogels were prepared by varying the ratios of chitosan and Fe3O4. These hydrogels including non magnetic hydrogel were compared with each other towards the removal of DBP and DEHP. Different characterization techniques such as FTIR, SEM, TG-DTA and XRD confirmed the successful fabrication of hydrogels. DSC measurements also indicated that total free water contents was maximum on gel with no magnetic particles. The gel with no magnetic particles was more hydrophilic and therefore not a suitable adsorbent for DBP and DEHP removal. However, the gels with optimum chitosan and Fe3O4 contents were more suitable for DBP and DEHP removal. Kinetically, the adsorption on both magnetic and non magnetic hydrogels was pseudo second order type. While equilibrium studies showed that one of the magnetic hydrogels preferred DEHP adsorption by Langmuir isotherm with adsorption capacity 1.93 mg/g but for DBP Freundlich isotherm was favorable with adsorption capacity 2.21 mg/g, while non magnetic gel favored adsorptions of DBP and DEHP by Freundlich isotherm with adsorption capacities 0.18 and 2.35 mg/g respectively. The effect of humic acid concentration left a very bad impact on non magnetic hydrogel as compared to the magnetic hydrogel. The influence of Na+, Ca2+ had salting out effect on magnetic gel while non magnetic gel promoted salting in effect. Thermodynamics of adsorption was exothermic. The mechanism of adsorption of non magnetic hydrogel was dominated by hydrogen bonding due to participation of NH and OH groups of chitosan and poly vinyl alcohol. Complexation with Fe3O4 was found to be the synergistic mechanism which enhanced the adsorption efficiency of magnetic hydrogels as compared to non magnetic hydrogels. Part 5 of the thesis is based on the exploration of adsorption performance of poly aniline coated montmorrilonite (PANI/MMT) clay composites for DEHP removal. The formation of PANI/MMT composites were confirmed with the help of FTIR, XRD, SEM, AFM and zeta potential analysis. Different experimental parameters influencing the adsorption efficiency of the composites were studied and compared with bare montmorrilonite (MMT). The adsorption of DEHP on MMT and PANI/MMT were maximum at 3 hrs with pseudo second order being favorable for MMT while pseudo first order with PANI/MMT. The maximum adsorbent dosage for DEHP was found to be 35 mg PANI/MMT and 50 mg MMT respectively. The adsorption mechanism for PANI/MMT favored partition mechanism while MMT supported Langmuir type mechanism. Influence of Na+ and Ca2+ had salting out effect with MMT while adsorption on PANI/MMT was independent of either concentration. Influence of solution pH indicated that adsorption of DEHP was maximum at pH 2 on MMT while adsorption of DEHP was independent of pH on PANI/MMT. Humic acid left a bad impact on PANI/MMT which is the main drawback of this adsorbent. The application of these materials in real water samples showed worthy performance.
Gov't Doc #: 16943
URI: http://prr.hec.gov.pk/jspui/handle/123456789/13216
Appears in Collections:PhD Thesis of All Public / Private Sector Universities / DAIs.

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