Dialkyldithiophosphate substituted on poly(vinylchloride): Synthesis and performance

Abstract

SYNOPSISPreparation of sodium salt of di (2-ethylhexyl) dithiophosphoric acid ( DTPANa) by reaction of the corresponding DTPA with sodium hydride has been described. Nucleophilic substitution of chlorine on poly( vinylchloride) (PVC) by a di( 2-ethylhexy1)dithiophosphate group resulting in modified polymer (MP) was characterized by the second order rate constant equal to 6.6 X M-' INTRODUCTIONIn recent years, a great amount of work has been done on the substitution of chlorine in poly( vinylchloride) (PVC) by nucleophiles such as thiolate, xantate, and dithi~carbamate.'-~ The substitution of chlorine in PVC was reported to produce a material for membranes used in per~aporation.~ A gelled membrane composed of PVC modified by dialkyldithiocarbamate with a specific extractant played as both an ion carrier and a solvent was recently de~cribed.~ The membrane was shown to be capable of selective separation of mercury or silver from many other cations when di(2-ethylhexyl) dithiophosphoric acid (DTPA) was used as an ion carrier. DTPA is a very strong extractant for a number of metals with the extraction sequence as follows:The excellent extraction properties of DTPA are already used in solvent-extraction plants in which metals are being recovered from low grade residues in the hydrometallurgical i n d~s t r y .~ Hence, it was of interest to find a way to introduce DTPA into a polymeric system giving material to be packed in ion exchange columns. To do so, we modified PVC by dithiophosphate. The resulting modified polymer ( M P ) formed stable gelled phases with DTPA. The synthesis and performance of the above MP are outlined below. EXPERIMENTAL Synthesis of DTPANaDTPA was synthesized by the reaction of 2-ethylhexyl alcohol ( Merck) with phosphorus pentasulfide (BDH Chemicals) according to a procedure described recently.' DTPA (0.01 mol) was carefully mixed with sodium hydride (0.01 mol) suspension (Merck) in water-free conditions until no more hydrogen was evolved from the reactionary mixture. The NaH was added slowly into DTPA with stirring to avoid excessive frothing. Bis [ di ( 2-ethylhexyloxy) thiophosphoryl] disulfide (BTPD) was synthesized and purified as was described elsewhere.' The resulting DTPANa, DTPA, and BTPD were analyzed by 'H and 31P NMR. To this solution DTPANa (0.03 mol) in DMF (20 mL) was added. The mixture was stirred under a stream of nitrogen at 45°C. Samples were withdrawn intermittently from the reactionary mixture and precipitated in methanol. The polymer was washed with water to remove the unreacted DTPANa, washed again with methanol, and dried under vacuum at room temperature.The sulfur and chlorine content of each sample was measured by elemental sulfur and chlorine analysis. NMR spectra were recorded at 400 MHz on a Bruker AMX400 spectrometer. A Nicolet 510 FTIR spectrometer was used to record infrared spectra of the modified polymer cast as thin films. Preparation of Beads and Ion Exchange ProcedureThe mixture of MP (S, 4.1%; C1,42.1%), PVC, and DTPA in the weight ratio 1.0 : 0.9 : 1.1 wa...

Magnetic Lyogels for Uranium Recovery from Wet Phosphoric Acid

“…Synthesis of PVC functionalized by dithioalkyl moieties such as N,N-dialkyldithiocarbamates and O,O-dialkyldithiophosphates by nucleophilic substitution in dipolar aprotic solvents has been reported previously. − , In this work, we chose N,N-diethyldithiocarbamate (DEDTC) and diethyldithiophosphate (DEDTP) as representative examples of dithio-functional compounds that are well-known chelators of heavy metals. ,− The nucleophilic substitution of PVC with DEDTC in dipolar aprotic solvents such as DMF proceeds at moderately elevated temperatures via neighboring group participation through the formation of an intermediary cyclic carbocation (Figure a). , The overall substitution degree, i.e., SD, % = 100 p / n or 100 q / n in Figure b,c is readily found from the elemental analysis.…”

“…A unique polymeric system that exhibits no syneresis when polymer is blended with a specific extractant is obtained by modifying halopolymers by substitution with a moiety of a substance compatible with the specific extractant . That is, if a halopolymer such as acid-resistant poly­(vinyl chloride) (PVC) or the like polymer is covalently modified with a molecule that closely resembles properties of the chosen extractant, the resulting modified polymer can form stable gels with such liquid organic extractants. − …”

Polyvinyl chloride modifications, properties, and applications: Review

“…A myriad of molecular and macromolecular substituents has been attached utilizing well‐known and appropriate organic reactions 12 . Indeed, chemically modified PVCs have found various applications, from ion‐selective electrode membranes and membrane sensors 13–15 to ion‐exchange columns for metal separation 16 . Chemical modifications of PVC started more than a half‐century ago and have been surveyed 12,17–19 .…”

Thorium (IV) ion-selective transport through a bulk liquid membrane containing 2-thenoyltrifluoroacetone as extractant-carrier

“…Acidic ligands are frequently used as extractant-carriers for separation of metal ions [12][13][14][15]. One of the most important advantages of such systems is the possibility to tune the selectivity and efficiency of the transport by controlling the pH of the aqueous feed and/or receiving phases.…”