Synthesis And Application of Ethylenediamine Triaceticacid Polysiloxane Immobilized Ligand System Prepared by Mohammad R. Matar &Hussein Al. Shayah Chemistry Department Islamic University of Gaza Supervised by : Dr. Nizam M. El-Ashgar

Polymeric Supports Polymeric Supports 1. Organic Polymeric Supports. are formed in two general ways. a) Addition Polymers:

 b) Poly condensation Polymers:

Disadvantages of Organic Polymers i- They are unstable under high pressure and disintegrate into smaller fragments, so clog up columns at high pressure chromatographic operations. ii- They are sensitive to high temperature and radiation. iii- They swell in most organic solvents. iv- Lack of chemical and mechanical stability. So it is very important to search for other polymeric matrices which have superior properties. So it is very important to search for other polymeric matrices which have superior properties.

2- Inorganic Polymeric Supports Polymers synthesis from elements other than carbon they are macromolecules in which a metal or metalloid is part of the main chain backbone (soil, diamond, glass, stones, graphite silica gel,………..)

Advantages Physical rigidity and high mechanical resistivity. Physical rigidity and high mechanical resistivity. Negligible swelling in both aqueous and organic solutions. Negligible swelling in both aqueous and organic solutions. Chemical inertness to analyte or production of side reactions. Chemical inertness to analyte or production of side reactions. High biodegradational, photochemical and thermal stability. High biodegradational, photochemical and thermal stability. Good mechanical and heat transfer properties. Good mechanical and heat transfer properties. Have good ability to withstand high pressure. Have good ability to withstand high pressure. Greater control for diffusion factors. Greater control for diffusion factors.

Polysiloxanes Immobilized Ligand Systems.  Functionalized polysiloxane sorbents (Polyorganosiloxanes).  Insoluble cross-linked organosilicon polymers with a controllable porous structure.  They are intermediates in composition between the pure inorganic silica and organic polymers such as polystyrene.  Although the chain is entirely inorganic, with alternating Si and O atoms, organic side groups are attached to the silicon atoms.  Has an extraordinary flexibility of the siloxane backbone.  Si-O bond is significantly longer than the C-C bond.  Si-O-Si bond angle of 143 > tetrahedral angle.

Important applications  Elastomers - Membranes, - Electrical insulators, - Water repellent sealants, - Adhesives, - Protective coatings – Hydraulic - Heat transfer - Dielectric fluids - Biomaterials - Catalyst supports - Stationary phase in liquid chromatography - Extraction and separation of metal ions from solutions.

Preparation of Polysiloxane immobilized Ligand System Method 1: The Sol – Gel Process: Hydrolytic polycondensation of a mixture of tetraethyl orthosilicate (TEOS) and the appropriate silane coupling agent in a definite mole ratio using acid or base catalysts. Hydrolytic polycondensation of a mixture of tetraethyl orthosilicate (TEOS) and the appropriate silane coupling agent in a definite mole ratio using acid or base catalysts. Method 2: Modification of the preformed polysiloxane immobilized ligand system by the appropriate ligand group. Sol-gel Process. Used for incorporation, immobilization, entrapment, and encapsulation for large variety of materials include; organic, inorganic, biomolecules, microorganisms, tissue and indicators.

Steps of the Sol-gel Process 1- Hydrolysis. By mixing low molecular weight tri or/and tetra alkoxysilanes with water in present of a homogenization agent. The hydrolysis catalyzed by acid or base.  SiOR + H2O  SiOH + ROH 2- Polycondensation. Through silanol-silanol condensation  SiOH +  SiOH  Si-O-Si  + H2O silanol-ester condensation.  SiOR +  SiOH  Si-O-Si  + ROH Where: R = CH 3 or C 2 H 5.

Formation of Solid Silica: Hydrolysis: Condensation.

Further polycondensation to form SiO2 net work The H 2 O and alcohol expelled from the reaction remain in the pores of the network.

Gelation, Drying and Aging. Gelation. Interconnection between particles of the sol increases forcing the sol to become more viscous (gel-point) so lose its fluidity. Drying. *Evaporation of water and organic solvent from the pores of the glassy material. *Shrinking of solid gradually (In some cases, the final volume of the xerogel is  10% of the initial volume of the gel). * Large internal pressure gradients in the wet pores. This process causes cracking and fracture in large monoliths. Addition of surfactants, such as Triton-X, were suggested to prevent these fractures * Large internal pressure gradients in the wet pores. This process causes cracking and fracture in large monoliths. Addition of surfactants, such as Triton-X, were suggested to prevent these fractures * Drying the wet gel under monitored conditions also, give free cracks monolith

 Aging.  Structure and properties of the gel continue changing with time.  The reaction, is completed further hydrolysis and resterification.  Polycondensation reactions – New bonds formation - are still occurs as a function of time.  Additional cross-linking and spontaneous shrinking occurs  The strength of the gel increases with aging   SiOR + H 2 O  SiOH + ROH   SiOH +  SiOH  SiOSi  + H 2 O

Preparation Methods Polysiloxanes 1- Sol-Gel Method. 2- Modification Method R = Me or Et R’ = Organofunctionalized ligand

Advantages of Polysiloxane Immobilized Ligand Systems.  The physical rigidity of their structures.  High abrasion resistively.  Negligible swelling in both aqueous and organic solutions.  Chemical inertness (low interaction with analytes).  Slower poisoning by irreversible side reactions.  High biodegradation, photochemical and thermal stability.  High capacity of functionalized groups.  Uniform distributions of ligand sites within the polymer particles.  Readily modified by a variety of functional groups to be immobilized either before or after polymerization.

 Drawbacks of Polysiloxanes.  Hydrolysis at high pH pH  12).  Unstable for certain reaction conditions.  Leaching of the functional groups from the support surface into the solution.  Application of Polysiloxane Immobilized Ligand Systems.  The extraction and and isolation of metal ions.  Metal ion separation in columns chromatography.  As catalysts in a variety of reactions.

Preparation of ethylenediaminetriacetic acid polysiloxane immobilized ligand system 1- Preparation of the silane agents by the reaction of 3- ethylenediaminetrimethoxysilane with ethylchloroacetate by the ratio of 1:2

2- Hydrolytic polycondensation of the triethyldiminotriacetatetrimethoxysilane agent with tetraethylorthosilicate (TEOS), in the ratios 1:2 respectively. 3- The new functionalized ligand system P-EDTA was obtained by acidic hydrolysis of the ester products.

Characterization of Functionalized Polysiloxanes. 1- Elemental Analysis: Polysilox ane %C%H%NC/N P- EDTE A Expected Found P-EDTA Expected Found

2- FTIR

Metal Uptake Capacity Maximum Uptake Co 2+ Ni 2+ Cu 2+ mg M 2+ /g Ligand mmol M 2+ /g Ligand

Effect of pH Uptake of metal ions by P-EDTA versus pH values, (72 hr shaking time ) Uptake of metal ions by P-EDTA versus pH values, (72 hr shaking time )

Chromatographic study Effect of pH on metal desorption Amount of Cu(II) desorbed as a function of eluent volume at different pH values (flow rate 1.5 mL/min)

Relation between total amount of Cu(II) desorbed & adsorbed as a function of pH Amount of Cu(II) desorbed and retained at different pH values (flow rate 1.5 mL/min).

Metal ions Separation Separation of Co(II), Ni(II) and Cu(II) at different pH values (flow rate 1.5 mL/min

Conclusion The immobilized ethylenediaminetriacetic acid ligand system was prepared by the sol-gel method. This immobilized ligand system exhibits high potential for extraction and separation of Cu(II), Ni(II) and Co(II) from aqueous solution.. The ligand system has been shown to be an effective solid-phase for metal ion recovery at the optimum pH.

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