SYNTHESIS AND EVALUATION OF A NOVEL SERIES OF NONIONIC SURFACTANTS DERIVED FROM ITACONIC ACID ESTERS AS BIODEGRADABLE CORROSION INHIBITORS FOR ALUMINUM IN ACIDIC MEDIUM

Manal El Hefnawy 1 , Abd El Menam Eissa 2 and Mohamed Deef Allah 1 . 1. Chemistry Department, Faculty of Engineering, Benha University, Benha, Egypt. 2. Chemistry Department, Faculty of Science, Benha University, Shoubra, Egypt. ...................................................................................................................... Manuscript Info Abstract ......................... ........................................................................ Manuscript History

A novel series of nonionic polymeric surfactants based on triethanolaminediesteritaconate have been prepared and characterize using FTIR and 1 H-NMR spectra. The surface activity, the surface parameters and the free energies of adsorption and micellization of these surfactants at three different temperature were also determined and correlated to their chemical structures .The biodegradability test of all the prepared surfactants revealed that they have a higher tendency towards biodegradation as the biodegradation ratio of them ranged from 88-100% after 7 days only of the exposure to the microorganism which specified them as highly biodegradable compounds .The synthesized nonionic surfactants were evaluated at different concentration as corrosion inhibitor of aluminum in 1M HCl solution using gravimetric analysis and potentodynamic polarization measurement .It was observed that the synthesized surfactant with lowest CMC values showed inhibition efficiency reach 93.7% after 4 h immersion and the inhibition efficiencies increase by increasing concentration of the studied surfactants and based on the potentiodynamic polarization results, the synthesized compound behaved as a mixed type inhibitors. SEM of the metal surface supported the inhibition effect of these surfactants.

…………………………………………………………………………………………………….... Introduction:-
There have been recent moves to reduce the use of certain classes of surfactants polluting the environment and to replace them with more environmentally friendly and cost efficient surfactants The use of the nonionic surfactants is a current trend in research to replace the charged anionic and cationic surfactants by more environmentally safe surfactants also producing new biodegradable surfactants from renewable resources is another trend. ( Itaconic acid (IA) is an unsaturated dicarboxylic acid, nontoxic and readily biodegradable. (IA) is industrially produced in a high yield through the fermentation of starch. It was listed as one of the top value added chemicals from bio-mass by the US Department of energy. (Werpy et al.,(2004)), (IA) and its derivatives due to their unique structures and characteristics can be used as starting materials for the synthesis of polymers (Dwiartil et al,(2007).Furthermore, it shows great potential in synthesis of polymerizable surfactants, however, up to date, there Preparation of triethanolaminediesteritaconate:-Triethanolamine (0.1mol) was esterified by (0.1 mol ) of monoester itaconic acid using xylene as a solvent and ptoluene sulfonic acid as a catalyst .At the end of the reaction ,when the theoretical amount of water was removed (1.8ml), the product washed by NaHCO 3 solution at 40 0 c to neutralize the catalyst, then triethanolamine diesteritaconate was extracted three times by petroleum ether(50 ml).Solvent was stripped off by rotator evaporator followed by complete drying of the ester using dry oven at 30 0 c under vacuum (Negm,2000).
Oxypropylation of triethanolamine diesteritaconate:-0.5wt% KOH solutions containing 0.01 mol of the ester was stirred and heated to 70 0 c respectively, while passing a slow stream of nitrogen through the system to flush out oxygen. After stopping the nitrogen stream, the propylene oxide was dropping with continuous stirring and heating under an efficient reflux system to retain the propylene oxide .The reaction was conducted for different intervals of time ranging from 1-10 h. From the increment in the mass of the reaction mixture the average degree of propoxylation were determined (Morgos et al, (1983); Ahmed et al, (1996) .The selected average numbers of moles n are 5, 10, and 15 (monomer A).

Preparation of amide oxim (monomer B):-
Hydroxylamine hydrochloride (3.5g, 51mmole) in methanol (30ml) was added to sodium hydroxide (2.11g, 50mmole) in methanol (30ml) at-25 0 c, and insoluble solids were separated off by filtration. Acrylonitrile in methanol (20mmol, 40 ml) was dropped on this filtrate, after stirring for 24 h .at room temperature the mixture filtered again and evaporate .To the residue insoluble solid 50 ml of methylene chloride was added then the crude product was obtained by evaporation of the filtrate (Monomer B) (Eissa et al, 1994).

Preparation of nonionic surfactants (copolymerization reaction):-
The copolymer were obtained by the solution polymerization techniques.The monomers were placed in polymerization tubes and diluted with dimethyl formamide .The polymerization was initiate by adding 1 mol % benzoyl peroxide as a free radicals initiators.The tubes were flushed with nitrogen gas for about 20 min. then sealed and thermo stated at 65 0 c for about 17-30hr depending on the monomer pairs and composition .The copolymer were obtained by repreciptation from petroleum ether (40-60 0 ) and finally vacuum at 60 0 c.Then the product polymer was cooled and neutralized with Sodium hydroxide solution (Azab, 2005).Scheme 1 shows the chemical structures of the synthesized compounds.

529
Elemental Analysis:-The structures of the investigated surfactants were confirmed by infrared (FTIR) and nuclear magnetic resonance 'H-NMR). Infrared spectroscopic analysis was performed by KBr disk method using a Fourier transform infrared spectrophotometer (FTIR) and 'H-NMR spectra were recorded using Varian-300Mercury 300 MHZ spectrometer with TMS as an internal standard and DMSO-D 6 Gel Permeation Chromatography:-The molecular weights of the prepared surfactants were measured by GPC water Model 600 E and are provided in Table 2 Properties of the prepared surfactant:-Surface tension andCritical micelle concentration (CMC) measurements:-Surface tension was determined at room temperature by using a Du-Nouy international tensiometer with a platinum ring (Abdel-Salam et al, 2011), also interfacial tension were obtained using the same procedures as the surface tensions measurements (Han et al, 2009;Negm, 2013) and by plotting of the surface tension versus the -logarithm concentration of surfactant at temperatures 303,313 and 333K, the point of break was taken as the CMC value (Colwell et al, 1961).

Maximum Surface Excess max
The maximum surface excess max can be calculated according to equation (2) max …………….. (2) Where R is the universal gas constant (8.314 J mol -1 k -1 ) and T is the absolute temperature (t+273K), ( / ln c) is the slope of a plot of surface tension versus concentration curves below CMC at constant temperature.

Minimum surface Area (A min )
Minimum surface area (A min ) can be calculated using equation (3)

Biodegradability:-
The biodegradability test in river water of the prepared surfactants was carried out using the surface tension method (DU-Nouytensiometer, Kruss type K 6 ) using a platinum ring (Falbe, 1986) Gravimetric measurements:-The inhibiting efficiency to corrosion of the prepared surfactants was measure using a weightloss technique ( Emregul et al ,2004)) .The experiments were performed using aluminum specimens have total surface area 530 3cm 2 ,corrosive solutions of 1M HCl and three different surfactants concentrations (100, 300, 500 ppm ) prepared from doubly distilled water. The specimens were dipped in 100ml of the corrosive solution at30 o c for a period of four hours .The experiments were carried out on triplicate specimens in the present and absence of surfactant and the average corrosion rate and inhibitor efficiency were calculated using equation (4,5) .
Wherew 1 and w 2 are the weight of the specimen after and prior to immersion in the test solution A area of the specimen (cm 2 ), T is the immersion w free and w add are the weight loss of aluminum in the absence and presence of the tested inhibitors, respectively.

Electrochemical measurement:-
The potentiodynamic polarization method was used to determined the cathodic and anodic polarization curves for aluminum in 0.1MHCl in absence and presenceof different concentration of the synthesized surfactant the working electrode was made of aluminum embedded in Araldite holder with area 1cm 2 .Calomel electrode and Ptwirewas utilized as a reference and counter electrode respectively .The polarization curves were determined using Mensbergerpotentiostate PS6 with controlling softwarePS remote. All experiments were carried out at scanning rate of 2mv/sec.

Fi g (3):-relation between surface tension and -log concentration of the nonionic surfactants
The maximum surface area max in mol/cm 2 was calculated from equation (2) were listed in Where R is the gas constant (8.314) T is the absolute temperature (K), CMC is the effectiveness in (mN/m) and A min is the minimum surface area at interface by each molecule in nm 2 .The thermodynamic data show the negativity of both ΔG mic andΔG ads which reveal the spontaneous behavior of these two processes. Also, the more negativity of ΔG ads is evidence for the preferential tendency of the prepared surfactants towards adsorption at the air water interface rather than formation of micelles in the bulk of the solution , the values of ΔG mic decrease by increasing the number of polyoxyproplene units in the nonionic surfactant molecules which could be attributed to the increase in the solubility of the different analogous as the result of hydrogen bonds formation. On raising the temperature the negativity of ΔG mic and ΔG ads are increased due to the stability of the adsorbed and micelized surfactant molecules than the freely dispersed ones in the aqueous phase.

Hydrophilic -Lipophilic Balance (HLB), Emulsion stability:-
The hydrophiliclipophilic balance HLB of a surfactant is a measure of the degree to which it is hydrophilic or lipophilic, and is determined as described by Griffin (Griffin, 1949). The calculated HLB values of the synthesized compounds (listed in table 2) showed high solubility of them in both water and oil phase and according to their HLP valueswhich ranged between 7and 11the synthesized surfactant were classified as water in oil emulsifiers, also these HLB values qualifies these surfactants to be applicable in interfacial application mainly corrosion inhibition (Varka et al,2004 ) Table (2) shows also the emulsion stability of this surfactants and reveals that it increased with increasing the hydrophilic chain length.

Weight Loss Measurements:-
The values of corrosion rates and inhibition efficiency obtained from the weight loss experiments are shown in Table 4. It is observed that the corrosion rate is gradually decreased by increasing the concentration of the inhibitors that may be attributed to the increase in the adsorbed amounts of the inhibitors on the metal surface which protect it from corrosive medium .It was also observed from the table as the polyoxypropylene unit increases the corrosion efficiency increase. The synthesized inhibitors have polyoxypropylene chains, amide oxime group and a great number of double bonds(C=O) and hetero atoms (N, O) in their chemical structures. This unique structure beside these highly electronegative groups make it can easily adsorbed on the metal surface which increases the efficiency of these inhibitors considerably .The corrosion inhibition efficiencies of the synthesized inhibitors are in the following order 3 > 2 > 1.

536
It was shown also from the table that the inhibition efficiency of the inhibitors within homologous series increases in the orderC 3 >B 3 >A 3 as the alkyl chain length increase and by correlated the data in ( Table 1 and 4) it was found that as the CMC value of the synthesize surfactants decrease the corrosion inhibition efficiencies values are increase becausethe lower CMC values indicate high repulsion in the aqueous bulk between water and surfactant molecules which increases the adsorption tendency of the inhibitors molecules at the metal interface, increases the monolayer formation on the metal surface, and consequently increases the inhibitors tendency.
In Fig (4)The corrosion rates were plotted against the immersion time at constant concentration of inhibitors (C 1, C 2 ,C 3) .It is clear from the Figure

Conclusion:-
New nonionic surfactants were synthesized and evaluated to be used as corrosion inhibitors of aluminum in1M HCl.The results of the study revealed the following: 1-The synthesized surfactants show good surface active properties, the negative values of ΔG ad s and ΔG mic implies that the two processes are spontaneous. The more negativity of ΔG ads confirming a higher tendency of the surfactant towards adsorption at the metal surface rather than micellization in the bulk of solution and among the studied system the lowest CMC values for surfactant C 3 were support it to be the most effective corrosion inhibitors for aluminum in 1 M HCl. 2-The synthesized surfactants acts as environmentally friendly compounds as The biodegradation ratio of all of the prepared surfactants ranged from 88-100% after 7 days only of the exposure to the microorganism. 3-The result of gravimetric analysis and potentiodynamic measurement revealed that the studied surfactants act as goodinhibitors (referring to their corrosion inhibition efficiency values which reached 93.7% after 4 h immersion) 4-From the polarization data, it is clear that the inhibitor is a mixed type inhibitor. 5-Surface morphology of the metal supported the inhibitive effect of the synthesized surfactants.