dialkyl phthalates used as plasticizers include the following compounds : di -( 2 - ethylhexyl ) phthalate ; di -( heptyl , nonyl , undecyl ) phthalate ; di - n - octyl phthalate ; dibutyl phthalate ( dbp ); dicapryl phthalate ( dcp ); dicyclohexyl phthalate ( dchp ); didecyl phthalate ( ddp ); diethyl phthalate ( dep ); diethylhexyl phthalate ( dehp ); diheptyl phthalate ( dhp ); dihexyl phthalate ( dhxp ); diisobutyl phthalate ( dibp ); diisodecyl phthalate ( didp ); diisoheptyl phthalate ( dihp ); diisohexyl phthalate ( dihxp ); diisononyl phthalate ( dinp ); diisooctyl phthalate ( diop ); diisopentyl phthalate ( dipp ); diisotridecyl phthalate ( ditdp ); dimethyl cyclohexyl phthalate ; dimethyl phthalate ( dmp ); dinonyl phthalate ( dnp ); dioctyl phthalate ( dop ); dipentyl phthalate ; ditridecyl phthalate ( dtdp ); diundecyl phthalate ( dup ); heptylundecyl phthalate ( hup ); hexyl octyl decyl phthalate ( hxodp ); nonyl undecyl phthalate ( nup ); and octyl decyl phthalate ( odp ). the coal fly ash used in this research was from an electric power plant . diethyl phthalate ( reagent grade ) was purchased from a chemical supplier and was used without further purification . phthalic acid ( s grade ), ethyl benzoate ( s grade ), benzoic acid ( reagent grade ) and sodium hydroxide ( s grade ) were purchased from a chemical supplier and were also used without further purification . deionized distilled water was used as a solvent . two aqueous solutions of diethyl phthalate were prepared in concentrations of 1 . 0 × 10 − 4 mol / l and 1 . 0 × 10 − 3 mol / l , respectively . basic solutions of diethyl phthalate , phthalic acid , ethyl benzoate , and benzoic acid ( all at a concentration of 1 . 0 × 10 − 4 mol / l ) were prepared using a naoh aqueous solution with a naoh concentration of 0 . 10 mol / l . sample # 1 was prepared by placing 3 . 0 ml of the aqueous solution of diethyl phthalate having a concentration of 1 . 0 × 10 − 4 mol / l and 0 . 10 g of fly ash into an optical quartz cell ( path length 10 . 0 mm ). the diethyl phthalate solution and the coal fly ash were divided by a glass filter ( advantec gs - 25 ) in order to avoid the suspension of the fly ash . it was ascertained that the diethyl phthalate solution permeated through the glass filter and that the adsorption of diethyl phthalate onto the glass filter was negligible . this 3 . 0 ml sample was allowed to stand at room temperature in the dark . uv - vis absorption spectra of the solution were measured using a hitachi u - 3210 spectrophotometer . sample # 2 and sample # 3 were prepared by making suspensions consisting of 30 . 0 ml of the diethyl phthalate aqueous solution in concentrations of 1 . 0 × 10 − 4 mol / l and 1 . 0 × 10 − 3 mol / l and 1 . 0 g of the fly ash . thus , sample # 2 consisted of 30 . 0 ml of diethyl phthalate having a concentration of 1 . 0 × 10 − 4 mol / l and 1 . 0 g of the fly ash . sample # 3 consisted of 30 . 0 ml of diethyl phthalate having a concentration of 1 . 0 × 10 − 3 mol / l and 1 . 0 g of the fly ash . the samples were prepared in air - tight vessels and allowed to stand at room temperature in the dark . these suspensions were then filtered to separate the solution from the fly ash by using a membrane filter ( advantec c020a ) after various exposure ( reaction ) times . gas chromatography - mass spectrometry ( gc - ms ) of the solutions was performed using a shimadzu gcms - qp5000 . the resulting two aqueous sample solutions were injected into the gas chromatograph without extraction . blank tests showed that little organic substance was eluted from the coal fly ash by water alone . optimal molecular geometries and transition energies for diethyl phthalate , phthalic acid , ethyl benzoate , benzoic acid , and anions of phthalic acid and benzoic acid in water were calculated using the pm3 ( parametric method 3 ) and indo / s ( intermediate neglect of differential overlap / spectroscopic parametrization ) methods for the purpose of spectral assignment . the uv - vis absorption spectra of sample # 1 ( consisting of an aqueous solution of 1 . 0 × 10 − 4 mol / l diethyl phthalate exposed to the fly ash ) were observed as a function of reaction time . fig1 a shows the changes in the spectra of sample # 1 and fig1 b the changes in absorbance of sample # 1 at 218 nm , 235 nm , and 276 nm . in fig1 a , the spectrum observed just after preparation ( at time ( 1 ) of 0 hours ) of sample # 1 shows the typical absorption spectrum of diethyl phthalate and exhibits two maxima at 235 nm and 276 nm . as shown in fig1 b , the intensity of absorbance at 235 nm and 276 nm gradually decreased with time while the absorbance at 218 nm increased gradually with time . the band found at 276 nm shifted to the shorter wavelength side with time and became broader than the band for diethyl phthalate . the degree of change of the spectrum became smaller after time ( 7 ) 60 hours of reaction time with the fly ash . [ 0024 ] fig2 shows a comparison of the absorption spectra of diethyl phthalate ( spectrum 1 ) and ethyl benzoate ( spectrum 2 ) in water , and of phthalic acid ( spectrum 3 ) and benzoic acid ( spectrum 4 ) in aqueous naoh solutions . according to the results of the indo / s calculations , the absorption bands at 235 and 276 nm of diethyl phthalate ( spectrum 1 ) are due to some transitions having different characters . the main contributions are homo ( highest occupied molecular orbital ) to lumo ( lowest unoccupied molecular orbital ) ( 75 %) and next homo to next lumo ( 16 %) configurations for the 235 nm band and homo to next lumo ( 38 %) and next homo to lumo ( 48 %) configurations for the 276 nm band , respectively . the transitions neglected included the n − π * character for the 276 nm band because its contribution was small and the n − π * level tends to be estimated lower in the case of aromatic carboxyl compounds . the assignments for diethyl phthalate essentially coincide with those for ethyl benzoate , phthalic acid and benzoic acid . phthalic acid and benzoic acid exist as their carboxylate anions in the basic solutions . on the other hand , diethyl phthalate and ethyl benzoate were gradually hydrolyzed to form the carboxylate anions of phthalic acid and benzoic acid in such basic solutions , respectively . the transition characters for the anions of phthalic acid and benzoic acid are different from the neutral phthalic acid and benzoic acid , and the esters , diethyl phthalate and ethyl benzoate . the broad bands at around 230 nm and 270 nm for the phthalic acid dianion , which are blue - shifted from those of diethyl phthalate , consist of homo to next lumo ( 57 %) and next homo to lumo ( 35 %) configurations for the 230 nm band and homo to lumo ( 58 %) and next homo to next lumo ( 35 %) configurations for the 270 nm band , respectively . the assignments for the phthalic acid dianion essentially coincide with those for the benzoic acid anion . the major spectral change shown in fig1 a explains the transformation from diethyl phthalate to the anion of phthalic acid , supposedly , via the ethyl phthalate anion . in practice , the ph range of the solution was 10 - 11 . this value indicates that such weak acid exists as an anion in the aqueous solution including the fly ash , which supports these results . the spectrum observed after 170 hours , however , has a shoulder around 220 nm and somewhat different shape from the anion of phthalic acid . inclusion of the benzoic acid anion and some other constituents due to the decomposition of phthalic acid anion makes the difference . these results indicate that the adsorption of phthalic acid on the surface of the fly ash particles occurred first and then some chemical reactions took place . [ 0027 ] fig3 a shows the gas chromatography - mass spectrometry ( gc - ms ) chromatograms of diethyl phthalate solutions having a concentration of 1 . 0 × 10 − 4 mol / l ( sample # 2 ) after being exposed to the fly ash for ( 1 ) 0 hours , ( 2 ) 24 hours , and ( 3 ) 170 hours . in fig3 a , the peaks located at 7 . 8 and 10 . 8 minutes can be assigned to benzoic acid ( ba ) and diethyl phthalate ( dep ), respectively . the peak intensity at 10 . 8 minutes became smaller with the progress of the reaction compared to that observed just after the sample preparation . the peak attributed to benzoic acid ( ba ) was observed in the sample runs after 24 hours of exposure to the fly ash and almost disappeared after 170 hours of exposure to the fly ash . these changes in the graph indicate that benzoic acid ( ba ) was produced in the decomposition of diethyl phthalate ( dep ) and then decomposed . the decomposition of diethyl phthalate ( dep ) and the production of benzoic acid ( ba ) correspond to the results of spectral measurements . phthalic acid , which is the intermediate product of the reaction from diethyl phthalate ( dep ) to benzoic acid ( ba ), was hardly detected in the runs . the disappearance of benzoic acid ( ba ) indicates a possibility of the production of volatile compounds , which are difficult to detect . [ 0028 ] fig3 b shows the gas chromatography - mass spectrometry ( gc - ms ) chromatograms of the diethyl phthalate solution having a concentration of 1 . 0 × 10 − 3 mol / l ( sample # 3 ) after being exposed to the fly ash for ( 1 ) 0 hours , ( 2 ) 24 hours , and ( 3 ) 170 hours . in fig3 b , the peaks located at 7 . 6 , 7 . 8 and 10 . 8 min can be assigned to ethyl benzoate ( eb ), benzoic acid ( ba ), and diethyl phthalate ( dep ), respectively . the diethyl phthalate ( dep ) peak became smaller with the progress of the reaction in the same way of fig3 a . the peaks attributed to ethyl benzoate ( eb ) and benzoic acid ( ba ) were observed in the sample runs after being exposed to the fly ash for 24 hours ( time 2 ) and 170 hours ( time 3 ). these results indicate the decomposition of diethyl phthalate ( dep ) and the production of ethyl benzoate ( eb ) and benzoic acid ( ba ). ethyl benzoate ( eb ) and benzoic acid ( ba ) were produced from ethyl phthalate anion and phthalic acid anion , respectively , which were the products from the hydrolysis of diethyl phthalate ( dep ). in the case of this 1 . 0 × 10 − 3 mol / l diethyl phthalate ( dep ) sample ( sample # 3 ), it took longer time to hydrolyze from diethyl phthalate ( dep ) to phthalic acid anion than in the case of the 1 . 0 × 10 − 4 mol / l diethyl phthalate ( dep ) sample ( sample # 2 ), so that there was a certain amount of ethyl phthalate anion to change into ethyl benzoate ( eb ). ethyl phthalate and phthalic acid , however , were not detected by the gc - ms analysis . it is probable that the anions of ethyl phthalate and phthalic acid in aqueous phase were efficiently adsorbed on the fly ash during the filtration before the gc - ms analysis because the membrane filter , having quite small pores ( 0 . 2 μm ), was clogged by the fly ash particles . the neutral ethyl phthalate and phthalic acid were actually detected from solutions extracted with an organic solvent . the coal fly ash consists of sio 2 ( 50 . 5 % by wt . ), al 2 o 3 ( 22 . 7 % by wt . ), cao ( 9 . 6 % by wt .) and na 2 o ( 1 . 4 % by wt .). the cao and na 2 o react with h 2 o and form ca ( oh ) 2 and naoh , which are dissolved in the aqueous solution . the diethyl phthalate solution including the fly ash indicated basic . considering the solubility of ca ( oh ) 2 in water , half of that included in the fly ash are not dissolved in the solution . the ca ( oh ) 2 sites existing on the surface of the fly ash particle act as a strong base . while not desiring to be bound by this theory , it is believed that the alkaline constituents hydrolyzed diethyl phthalate in the liquid phase suspending the fly ash to form ethyl phthalate and / or phthalic acid , which were adsorbed on the fly ash and then decarboxylated on the surface of the fly ash . the pathways of these reactions are shown in fig4 . the carboxylic groups of ethyl phthalate and phthalic acid interacted with the ca ( oh ) 2 sites and were decarboxylated to form ethyl benzoate ( eb ) and benzoic acid ( ba ), respectively . then these compounds were desorbed into the liquid phase . in the case of the 1 . 0 × 10 − 4 mol / l sample ( sample # 2 ) ( fig3 a ), ethyl benzoate ( eb ) was hardly detected because the hydrolysis capacity of the fly ash is high compared with the concentration of diethyl phthalate needed to change ethyl phthalate into phthalic acid . the peak intensities of ethyl benzoate ( eb ) and benzoic acid ( ba ) in the gas chromatograms are relatively weak compared to the extent of the decrease in that of diethyl phthalate ( dep ), suggesting that other hardly - detected chemicals were also produced . on the other hand , the absorption spectra of the samples reacted for long time have a band in the wavelength range less than 220 nm , indicating the existence of benzene , benzene derivatives , and / or other volatile compounds of lower molecular weight . though the results are not shown here , the benzenes were also detected in the gas phase of the gas - tight vessel containing the samples . alkaline constituents eluted from the coal fly ash in the liquid phase gradually hydrolyzed diethyl phthalate to produce ethyl phthalate anion and / or phthalic acid anion . the carboxylic groups of the ethyl phthalate and the phthalic acid , which were adsorbed on the fly ash , interacted with the basic ca ( oh ) 2 sites and were decarboxylated to form ethyl benzoate ( eb ) and benzoic acid ( ba ), respectively . these products were gradually desorbed to the liquid phase . the formation of ethyl benzoate ( eb ) and benzoic acid ( ba ) was followed by the decomposition into benzenes and / or the other volatile compounds of lower molecular weight . thus , coal fly ash is able to decompose dialkyl phthalates , which are endocrine disruptors . the process can be performed wherein the concentration of the dialkyl phthalate is from 1 . 0 × 10 − 5 mol / l to 1 . 0 × 10 − 2 mol / l and from 1 . 0 × 10 − 4 mol / l to 1 . 0 × 10 − 3 mol / l . the dialkyl phthalate can be di -( 2 - ethylhexyl ) phthalate ; di -( heptyl , nonyl , undecyl ) phthalate ; di - n - octyl phthalate ; dibutyl phthalate ( dbp ); dicapryl phthalate ( dcp ); dicyclohexyl phthalate ( dchp ); didecyl phthalate ( ddp ); diethyl phthalate ( dep ); diethylhexyl phthalate ( dehp ); diheptyl phthalate ( dhp ); dihexyl phthalate ( dhxp ); diisobutyl phthalate ( dibp ); diisodecyl phthalate ( didp ); diisoheptyl phthalate ( dihp ); diisohexyl phthalate ( dihxp ); diisononyl phthalate ( dinp ); diisooctyl phthalate ( diop ); diisopentyl phthalate ( dipp ); diisotridecyl phthalate ( ditdp ); dimethyl cyclohexyl phthalate ; dimethyl phthalate ( dmp ); dinonyl phthalate ( dnp ); dioctyl phthalate ( dop ); dipentyl phthalate ; ditridecyl phthalate ( dtdp ); diundecyl phthalate ( dup ); heptylundecyl phthalate ( hup ); hexyl octyl decyl phthalate ( hxodp ); nonyl undecyl phthalate ( nup ); and / or octyl decyl phthalate ( odp ). the ph can be 9 to 12 and the ph can be 10 to 11 . the time of exposure to the coal fly ash can be from 1 to 200 hours and the time of exposure to the coal fly ash can be from 50 to 170 hours . from 10 grams to 50 grams of coal fly ash can be used for each liter of aqueous solution containing the dialkyl phthalate . and 20 grams to 40 grams of coal fly ash can be used for each liter of aqueous solution containing the dialkyl phthalate . one practical application for the present process is to decompose dialkyl phthalates which have been dissolved in water and removed from articles made of polyvinyl chloride ( pvc ), polyvinylidene chloride , and / or other synthetic resins , where dialkyl phthalates are used as plasticizers , such as in medical products and children &# 39 ; s toys . unless indicated otherwise , in stating a numerical range for a compound or a time or other process matter or property , such a range is intended to specifically designate and disclose the minimum and the maximum for the range and each number , including each fraction and / or decimal , between the stated minimum and maximum for the range . for example , a range of 1 to 10 discloses 1 . 0 , 1 . 1 , 1 . 2 . . . 2 . 0 , 2 . 1 , 2 . 2 , . . . and so on , up to 10 . 0 . similarly , a range of 500 to 1000 discloses 500 , 501 , 502 , . . . and so on , up to 1000 , including every number and fraction or decimal therewithin . “ up to x ” means “ x ” and every number less than “ x ”, for example , “ up to 5 ” discloses 0 . 1 , 0 . 2 , 0 . 3 , . . . , and so on up to 5 . 0 . while several embodiments of the invention has been illustrated and described , it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention .
decomposition of dialkyl phthalates exposed to coal fly ash is disclosed . alkaline constituents eluted from the fly ash in the liquid phase hydrolyze the dialkyl phthalate . the fly ash acts as not only an adsorber but also as a decomposer .