I n d . Eng. C h e m . Res. 1988,27, 1806-1810
1806
t = time, s
Literature Cited
Greek Symbols
Abdel-Thalouth, I.; Elzairy, M. E.; Hebeish, A. Am. Dyest. Rep. 1986, 75, 32. Carreau, P. J. Ph.D. Thesis, University of Wisconsin, Madison, WI, 1968. Cross, M. M. J. Colloid Sci. 1965, 20, 417. Eyring, H.; Ree, F. H.; Ree, T. Znd. Eng. Chem. 1958, 50, 1036. Morris, E. A. In Gums and Stabilizers for the Food Industry 2; Phillips, G . O., Wedlock, D. T., Williams, P. A., Eds.; Pergamon: Oxford, 1984, pp 57-78. Schurz, J.; Friesen, W.; Schempp, W. Das Papier 1975, 29, V7. Wielinga, W. C. Melliand Textilber. 1986, 1, 45. Williams, M. C.; Bird, A. B. Phys. Fluids 1962,5, 1126.
T = shear rate, l / s qc = characteristic shear rate, l / s 6 = phase lag, rad 11 = viscosity, Pa.s qo = zero-shear viscosity, PaBs 1.. = infinite-shear viscosity, P e s q* = complex viscosity, Pa.s 7' = dynamic viscosity, P e s X = characteristic time, s w = frequency, rad/s Registry No. HEG, 39465-11-7; CMC, 9004-32-4; ALG, 3005-38-3; Blue Telon 5G, 12219-38-4; Blue Palanil BGF, 12222-85-4;Procion Brown P4/RD, 12225-72-8.
Received for review January 26, 1988 Revised manuscript received May 23, 1988 Accepted June 6, 1988
Development of Novel Polymeric Soil Stabilizers? Shawqui M. Lahalih* and George Hovakeemian Kuwait Institute f o r Scientific Research, P.O. Box 24885, 13109 Safat, Kuwait
A composition of sulfonated urea-melamine-formaldehyde with poly(viny1 alcohol) was developed and tested on sandy soil for its stabilization. The use of this kind of composition as a soil stabilizer is novel and has not been revealed before. The compressive strength of sandy soil and its resistance to water erosion are significantly improved after it has been treated with this composition. It was found that, at an application rate of 1 % by weight of this composition to the weight of sand, the compressive strength of sand improved by a factor of 3. Erosion of sand by water was also reduced to zero after exposure to three cycles of 6 h, each interrupted by 24 h of curing at a water runoff rate of 6 L/min. The developed composition outperformed commercial soil stabilizers in the stabilization of sand. The results obtained are explained by a proposed mechanism for the mode of action of this composition with sandy soil. Soil erosion is a phenomenon occurring in a wide variety of situations. For example, it is a serious problem in countries with arid climates and in areas with little rainfall. Soil erosion problems are frequently caused by the existence of fine particles on the surface of the soil. These fine particles are poorly bonded and susceptible to erosion by wind and rain. In addition, the structure of the soil determines its properties such as permeability to water, porosity, crust formation, and load carrying capacity. Weak soil and sand structure cause problems in road and highway construction, steep slopes, water channels, construction, excavation banks, and landing sites for aircraft and the like. Extensive research has been carried out to improve soil structure, to reduce soil erosion, to reduce water evaporation, and to increase bonding strength so that it can withstand greater loads. The research has generally had one or two objectives, Le., to prevent or minimize soil erosion and to improve soil load-carrying capacity. For example, acrylamide polymer cross-linked with N,Nmethylenebis(acry1amide) was used by some researchers (Cooke, 1984a-c; Clark, 1984) with other additives such as palm nuts and seaweed as a water-absorbing material for agricultural application. Similarly, plant-growing media based on acrylamide polymers were reported by Clarke (1984), Bosley et al. (1983), and Helbing (1981). Other polymer-based materials were also used to stabilize the soil, such as cellulosic polymers with A1(OH)3 (Bryhn and Loken, 1984) or with latex (Janowisk, 1978), 'Publication No. KISR 2542. 088S-5885/88/2627-1806$01.50/0
lignosulfonates reacted with acrylic acid (Zaslavasky and Rozenberg, 1983), poly(acry1amide) reacted with polyaldehyde and hopohalites (Pilny, 1980,1982),and mixtures of dimer diisocyanate and dimer diamide (Reed and Morre, 1981) and polyelectrolytes (Eikhof and King, 1981). Others (Meknight, 1972) have used cationic polymer latexes prepared from acrylates and anionic lignin from cellulosic material to stabilize soil and prevent soil erosion by wind or water. Others used natural or synthetic rubber latexes with nonionic surfactants to stabilize soil (Bennet, 1977). In addition, Sakata et al. (1970) disclosed a process for forming a gellike material in a soil by injecting an aqueous solution containing three components into the soil. The aqueous solution includes urea, formaldehyde, and poly(vinyl alcohol) and is cured within the soil by the addition of an acidic substance. This process is useful for rendering a water-permeable soil water impermeable and thereby stabilizing it. A composition of poly(viny1 acetate) and cement improved the adhesion of sandy soil (Kazda et al., 1974). Poly(viny1 acetate) together with chlorinated poly(is0butane) was used to improve the resistance of sandy soil to erosion and to protect plants from damage by shifting sand (Regeaud and Trebillon, 1974). Poly(viny1acetate) was also used to consolidate soil by Sakata and Nakabayashi (1969). Poly(viny1 alcohol) stabilized fine sandy loam soil without any effect on plant growth or nitrogen uptake (Sefanson, 1974). Hydrophilic urethane prepolymer consolidated sand particles and produced a water-permeable sand that could 0 1988 American Chemical Society
Ind. Eng. Chem. Res., Vol. 27, No. 10, 1988 1807 Table 1. Chemical Composition of Kuwait Gatch Soil Used for Soil Stabilization compd percentage compd percentage SiOz 91.40 CaO 0.27 A1203 4.19 TiOz 0.09 KZO 1.50 0.66 MgO 0.44 L.O.I." 1.46
100 FD
BL 0 51 i
,a
1 io 0
"L.O.I. = loss on ignition (at 1000 "C).
0
3
sustain plant growth (Kistner, 1974). Polyurethane injection has been used to strengthen sandy slopes; no breakdown of the slopes was observed after 7 h of 2500 mm/h uniform rain (Asao, 1973). It can be seen from this brief review that soil-stabilizing materials were developed either as plant-growing media and water-absorbing gels or, in some cases, as additives to improve soil structures. Although most of the published patents have served one or more of these purposes, serious drawbacks still exist. For example, toxic monomers such as acrylamide could be detrimental if they leak to water lines or could cause a health hazard to the operator who is applying them. Other systems are difficult to apply because they require special techniques or equipment. Still others use soil stabilizers in solid form. In addition, some systems cure very slowly and may take a long time to gel and perform their function. These and other drawbacks such as the economics of these materials make them very limited in their applications. Therefore, it is the objective of this paper to report on the development of a novel water-soluble polymer that can be very effectively used as a soil stabilizer. Some results and a mode of action model will be presented and discussed.
Experimental Section Materials. Commercial grades of melamine, urea, paraformaldehyde, sodium metabisulfite, sulfuric acid, and sodium hydroxide were used to prepare sulfonated amino-aldehyde resins that were used in this study. Poly(viny1 alcohols) with different molecular weights were obtained from Fluka, A.G., Germany, and used as received. Tests were conducted on sandy soil obtained from a quarry in the Sulaibiya area in Kuwait. This type of sand is referred to as "gatch". The chemical composition of this type of sand is shown in Table I. The particle size analysis of this sand is shown Figure 1. Equipment. The pH was measured with a WTW Model 530 pH meter equipped with a combination electrode (WTW Model E50). The meter was calibrated periodically with standard buffer solutions. Viscosity was measured on a Haake CV-100 rotational viscometer standardized with standard oil samples. Compressive strength was measured by an INSTRON universal testing machine, Model 1195. Procedures. Preparation of the SUMF Polycondensates. The method for preparing the sulfonated
u Y e - 1 SIZE
mj
Figure 1. Particle size analysis of sample of Kuwait gatch soil used for soil stabilization studies (wet sieve analysis: 9.8% (10.075mm)).
urea-melamine-formaldehyde polycondensation products followed a modified procedure developed by Lahalih and Absi-Halabi (1987). The reaction is conducted in a 1-L reaction flask and involves four steps: hydroxymethylation, sulfonation, low pH condensation, and high pH condensation-rearrangement. The four steps are summarized below for a typical 0.5 mol scale reaction. Step 1. Paraformaldehyde (51.7 g, 1.72 mol) is dissolved in water (500 mL) in a jacketed reactor flask at 80 "C, and the pH is adjusted to 10 (NaOH; 6 N). After complete dissolution, melamine (37.8 g, 0.3 mol) and urea (12 g, 0.2 mol) are added all at once, and the reaction is stirred for 15 min at 80 "C. Step 2. To the solution obtained from step 1, sodium metabisulfite (38 g, 0.25 mol) is added, and the pH is readjusted to 10. The reaction is continued at 80 "C for 60 min. Step 3. The pH is lowered to a range of 3.0-4.5 (H2S04; 3 N), and the reaction is stirred at 80 "C for 60-120 min. Step 4. Finally, the mixture pH is raised to 9, and the reaction is continued at the same temperature for 40 min. After cooling, the resultant solution is diluted to a 10% solid solution, the pH is adjusted to 9, and poiy(viny1 alcohol) is added in a range of 0.01-0.05% by weight of sulfonated urea-melamine-formaldehyde (SUMF) solution. In experiments involving mixtures of melamine and urea, the formaldehyde used in these experiments was calculated so that the aldehyde-to-amine ratio was held constant whenever the ratio of melamine to urea was varied. Table I1 shows the various preparations. Testing of Soil Stabilizer Compositions on Soil. The following tests were adapted from Morrison (1971) and Zhordania et al. (1982). Compressive Strength. For control specimens, water (20 g) was mixed with 200 g of soil (
