Comparative Studies of Diffusion and Permeability of Synthetic Membranes for Electrolyte Ions in Solution

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October 2007 Volume 2 Issue 3 Physical CCHHEEAMMn InIIdSSiaTnT JRoRurYnYal Trade Science Inc.

Full Paper PCAIJ, 2(3), 2007 [217-219]

Comparative Studies Of Diffusion And Permeability Of Synthetic Membranes For Electrolyte Ions In Solution

E.N.Ejike2, I.A.Okoro*1, N.Ocho2 1Department of Chemistry, Michael Okpara University of Agriculture, Abia State, (NIGERIA) 2Department of Chemistry, Federal University of Technology, Owerri, Imo State, (NIGERIA) E-mail : Okoroia @yahoo.com. Received: 10th April, 2007 ; Accepted: 15th April, 2007 ABSTRACT KEYWORDS

The diffusion rate and permeability of electrolyte ions through some com- Synthetic membrane; mercial available synthetic membranes were investigated. The Electro- Electrolyte ions; lytes of interest were sodium chloride, calcium chloride, Aluminum chlo- Diffusion; ride, sulphamic acid and butyric acid. The effect of concentration varia- Membrane thickness. tion was also monitored for each of the electrolytes. The results obtained showed that the rate of diffusion of metal ions derived from these three electrolytes determines for concentration and membranes thickness (breakthrough time tb). Decrease in metal ion concentrations increase the diffusion rate while increasing membrane thickness causes an increase the rate of electrolyte in diffusion. The trend in the rate of diffusion is thus  Na+>Ca2+>Al3+>NH4+>H+. 2007 Trade Science Inc. - INDIA

INTRODUCTION erals, ions, macromolecules posion wastes as well as the removal of harmful chemicals from industrials, biological Synthetic membrane processes have emerged into system, mining effluents, domestic wastes and waste in versatile area of technology and play an increasingly water recovery[2,3]. Membranes are generally described important role in many economic sections: Industry, Ag- as natural (bio membranes) or synthetic membranes that riculture, medicine, biological system, scientific research, consist of spongy-complex network of materials which environmental pollution management to mention but a are permeable to some ions depending on sizes while few[1]. Electro membrane processes both natural(bio been impermeable to large size ions or molecules like membrane) and synthetic membrane that use ion- ex- protein carbohydrates, enzymes called macromol- change membrane and an electrical potential difference ecules[4,5]. as the driving force for ionic species have found numer- Synthetic membranes have been used by researches ous applications and are strongly gaining wide accep- to remove hazardous ions such Pb2+, As2+, Cd2+, in in- tance as efficient and economic alternatives to conven- dustrial effluents under concentration gradients in ab- tional methods of separation and purification, lot of which sence of applied electric potential[1,4,5]. are directly related to environmental pollution control. In this study we shall use the conductivity values There include recovery and reuse of valuable min- obtained at each concentration level of the electrolytes 218 Diffusion and permeability of synthetic membranes PCAIJ, 2(3) October 2007

Full Paper investigated using two different commercial available Two commercially available synthetic membranes membranes: nylon and high density polyethylene to more procured at ihieagwa market owerri North L.G.A., evaluate the diffusion rate and permeability of each of Imo state Nigeria and were identified and authenticated these synthetic membrane to electrolyte ions in solu- by a polymer chemist as nylon and high density poly- tions In order to determine the diffusion rate, the ficks ethylene membrane materials. law model was adopted and adapted. The rate of dif- All chemicals used are analytical grade reagents from fusion of the electrolyte ions shall be obtains thus:[6,7] may and baker chemicals, London. Preparation of syn-  Ddc thetic membrane for studies. J (1) dx Each of the synthetic membranes where J is the diffusion rate(Flux density) of electrolyte ion in horizontal bed area of the membrane(mols-1 M-2), dc/dx the Nylon and HDPE was cut out with respect to the change in the concentration of the electrolyte ions in mole per area of the outer radius of the bicell apparatus. Each of unit volume of membrane column at timet(mole/L) and D is the the pieces specifically cut was activated by soaking them electrolyte binary diffusion coefficients(M2S-1). in ethanol solvent for twenty minutes intervals, then each The permeability of the electrolyte ions shall be de- washed copiously with double distilled deionised wa- termined using the expression[8] ter. Then each of the cuts soaked in double distilled  2.303 Co deionised water for 48hr for membrane swelling. The Pt evlog  (2) 2A Co 2Ct swelling is to allow the resident of water molecules in Where Pt is the permeability of electrolyte ion at time t for each the membrane pores and enhanced the easily passage of the synthetic membrane system investigated, e is the (diffusion) of electrolyte ions. Electrolyte solution prepa- remembrane. Thickness e=0.06 cm for Nylon and e=0.01 cm for ration: 0.1M and 0.01M solutions of each of NaCl, High density polyethylene. V=the volume of permeability bicell CaCl .AlCl , NH SO OH(Sulphamic acid) and apparatus used, that is the volume of the solution used in the 2 3 3 2 bicell compartment A is the area of the membrane exposed to CH3(CH2)2 COOH electrolyte ion called permeant, t=the contact time interval for Solutions were prepared. The initial conductivity of diffusion and permeation to take place, Co is the initial electro- each of these electrolyte solutions and that of the double lyte ion concentration and Ct is the electrolyte ion permeant at distilled deionised water were measured using conduc- time t(the unit of permeability in cm2 Min-1). tivity meter (Beckman model). The breakthrough time tb for each synthetic membrane (Nylon and High density polyethylene) thickness Diffusion and permeation studies shall be calculated using the expression[6,7] Thirty milliliter of each of the five electrolyte solu- 2 tions prepared(0.1M and 0. 01M) respectively was mea- tb  0.756 I ¶ (3) sured out into the salt arm of the bi cell apparatus. The B 2 D ¶ two solution were separated by the already swelled cut where I=membrane thickness =a constant(22/7) and D is the of each of the synthetic membranes sequentially. This ex- diffusion coefficient. perimental set up was monitored at ambient time of 250C The area of membrane exposed is exposed thus at 30 minutes time intervals, for total of 180minutes ex- ¶ D2 perimental duration time, with continuous stirring of the A (4) 4 two solutions using battery powered magnetic stirrer. where D is the diameter of each membrane which is taken as 1.8cm At the end of each thirty minutes interval, 10 millili-

 2 ters of the double distilled deionised in the bi cell ap-  22 (1.8cm) Therefore A 7 2 paratus arm was drawn out and the conductivity mea- 2.55cm sured using the conductivity meter(Beckman model). In this work, we report the diffusion rate, and per- The whole procedures described above was exactly meability of two synthetic membrane: nylon and high repeated using each electrolyte solutions of 0.1M and density polyethylene to electrolyte ions in solution. 0. 01M concentrations respectively. A Schematic diagram of the bicell is showed below: MATERIALS AND METHODS Electrolyte solution Synthetic membrane Double distilled 30mLs swelled deonised water Sample collection C1 C2 Physical CHEAMn InIdSianT JoRurnYal PCAIJ, 2(3) October 2007 I.A.Okoro et al. 219

Full Paper RESULTS AND DISCUSSION and more water molecules residency in the high density polyethylene membrane when compared to the Nylon The results from the diffusion and permeability of membrane. This may be the reason for the ease with synthetic membranes: Nylon and high density poly eth- which the electrolyte ions cross the high density poly- ylene materials using equations 1,2,3 and 4 respectively ethylene membrane to the other section of the experi- are presented in TABLES(1 and 2). From TABLE 1, it mental set up in ceasing the conductivity of the double was observed that the diffusion rate of Ca2+ ion perme- distilled deionised water with time. This observation, ate is greater than the other electrolyte ions: Na+ Al 3+ implies that the high density polyethylene membrane is NH4+ and H+ in the nylon synthetic membrane. This more susceptible to ion permeability and ion diffusion trend is reverse in the high density polyethylene mem- that the nylon membrane(TABLE 1 and 2). brane in which Na+ ion has the greatest diffusion rate of From this study the preferential use of high density  4.00 10-3 unite per second(TABLE 2). The perme- polyethylene membrane is recommended in place of ability of the two synthetic membranes: nylon and high bio membranes for separation processes; water dialy- density polyethylene is influenced by the concentrations sis, electro dialysis, and other filtration uses involving of electrolyte solutions. The decrease in the concentra- certain ions especially toxic metal ions arising from waste tion of the electrolyte solution yielded higher values for waters and industrial effluents. permeability and diffusion rate. This may be explained in terms of hydration factor. In the less concentrated REFERENCES electrolyte solution, and so the ions are more free to [1] move and cross the membranes freely[9,10,11,12]. The time E.E.Oguzie, S.I.Okafor, A.I.Onuchukwu; Journal + 2+ of Chemical society of Nigeria, (in press) (2006). required for any of the five electrolyte ions; Na , Ca , [2] Al3+ NH4+ and H+ to permeate the membrane thick- R.B.Patel, J.M.Pandya, K.Lal; Physical chemistry ness measured by the factor; the breakthrough time tb trans, SAEST, 17(4), 321 (2006). [3] A.M.Mayout; Corros.Prev.Ctrl, 6, 68 (1996). is observed to be greater in the nylon membrane than in [4] L.L.Albert; Bio Chemistry, Worth publishers Inc., the high density polyethylene membrane(TABLE I and New York, 741-798 (1975). ‘ 2). This may be explained in terms of swelling effects [5] L.I.Rothfield; Structure and functions of biologi- ’ TABLE 1: Determined mean diffusion rate(Dr) mean perme- cal membrane , Academic press Inc, New York, 20-101 (1971). ability (P,) and break through time(tb) of electrolyte ions [6] through nylon membrane at 250C A.L.Derek; Electro chemistry, London press Inc, O. /M Concentration O.01/M Concentration London, 34, 18-216 (1989). Electrolyte [7] ‘ ’  -3  -7 tb  -3  -7 2 Tb K.A.Sinyder; Concrete science and Engineering , Solution Dr. 10 P 10 Dr. 10 P 10 cm umol/sec cm2 min-1 sec umol/sec min-1 sec 11-105 (2001). NaCl 3. 57 8. 22 7. 75 3. 84 1.79 7.20 ’ [8] P.A.Steward; Fick s law of diffusion online, elec- CaCl2 3. 85 5. 25 7. 18 3. 84 7. 49 7.20 AlCl3 3.57 5.44 7.75 3.33 7.28 8.29 tronic articles, 1-2 (2005). NH SO OH [9] 3 2 1. 43 3. 56 1. 94 1. 37 4.17 2. 05 K.San wan; Chemistry, M.I.N college publishers Inc, (Sulphamic acid) CH3(CH2)2COOH 0.82 4.52 2.24 1.56 4.63 1.77 India, 25-108 (1982). 2 ‘ (Butyric acid) [10] A.Akelah; Functionalized polymers and their Ap- ’ Data are means of four determinations plications, Chapman an Hall publishers , Inc New TABLE 2 : Determined mean diffusion rate(Dr) mean perme- York, 1-154 (1990). ‘ ability (P,) and break through time(tb) of electrolyte ions [11] A.I.Vogel; A text book of Quantitative In organic ’ through high density polyethylene membrane Analysis , Lowe and Bryclone Ltd, great Britain, O.1M concentration O . O 1M concentration 10-115 (1975). Electrolyte  -3  -7  -3  -7 Dr 10 P 10 Dr. 10 P 10 tb [12] solution tb Sec E.E.Oguzie, B.N.Okolue, C.E.Ogukwe, A.I. umol/Sec cm2min-1 umol /sec cm2min-1 Sec NaCl 4. 00 1. 68 1. 92 3. 57 1. 87 2. 15 Onuchukwu, C.Unaegbu; Bull.Electro Chem., CaCl2 2. 50 6. 79 3. 0,7 3. 45 8. 34 2. 22 20(9), 421 (2004). AlCl3 2. 50 6. 49 3. 07 2. 56 8. 27 2. 99 NH SO OH 3 2 1. 20 0. 68 6. 39 1. 57 0. 79 5. 67 (Sulphamic-acid) CH (CH ) COOH 3 2 2 1. 24 0. 82 6. 89 1. 49 0. 45 4. 48 (Butyric2 acid) Data are means of four determinations Physical CHEAMn InIdSianT JoRurnYal