Scientific registration n o : 728 Symposoum n o : 6 Presentation : Poster CHOUDHARY O.P., HUNDAL H.S., KUMAR S.

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1 Scientific registration n o : 728 Symposoum n o : 6 Presentation : Poster Competitive Adsorption of Phosphate, Molybdate, Borate and Silicate in Binary-anion mixture with soils Adsorption compétitive de phosphate, molybdate, borate, et silicate dans les mélanges binaires d anions et de sols CHOUDHARY O.P., HUNDAL H.S., KUMAR S. Department of Soils, Punjab Agricultural university, Ludhiana Introduction Soil solution and waste effluents used as irrigation water contain more than one kind of oxyanions and are capable of competing for adsorption sites and eventually influenced their absorption by growing plants. The adsorption data obtained for oxyanions in monocomponent soil system could, therefore, be misleading. The basic information on the interaction of phosphate, molybdate, borate and silicate in binary-anion mixtures is of particular importance in plant nutrition and to their transport in soil in relation to pollution hazards at waste effluent disposal sites. However, the information is lacking about the interaction of these anionic mixtures with soil. The present investigation was, therefore, undertaken to determine the competitive adsorption of phosphate, molybdate, borate and silicate in binary solute of anionic mixtures with soils as adsorbent. Material and Methods Two surface soil samples were collected from Andretta (Typic paleudulf) in Palampur and Haibowal (Typic Fluvaquent) in Ludhiana from N-W India. Andretta silt loam had ph 5.2, organic C 1.4% and amorphous Al and Fe were 939 and 1879 mg kg -1 soil, respectively. Haibowal silt loam had ph 8.80, organic C 0.43, CaCO % and amorphous Al and Fe were 280 and 1271 mg kg -1 soil respectively. Two sets of standard solutions of phosphorus, silicon, molybdenum and boron of varying concentrations were prepared in 0.01 m KCl solution. For single anion adsorption experiments, 25 ml of the standard solutions containing varying anion concentrations were added to 2.0 g soil. The soil solution ratio was maintained to 1:25 (W/V) by adding another 25 ml of 0.01 M KCl. The ph of the electrolytic solution prior to 1

2 their use for adsorption studies was adjusted to 4.2 and 8.0 for Andretta and Haibowal soil respectively. For competitive adsorption experiments varying concentration of first anion was added through 25 ml standard solution to 2 g of soil in 100 ml Teflon bottles. In binary anion mixtures, the constand concentration of competing anion was added through addition of 25 ml of standard solution to varying amount of first anion for each isotherm. All the single and competitive adsorption of anion experiments were made in triplicate. Adsorption isotherms were determined by equilibrating soil solution suspensions for six days in incubator maintained at o C. After equlibration soil solution suspension was separated by filtration through Whatman No.42 filter paper. Samples of different solutions were analysed prior to and after equlibrating anion with the soil samples for mono-anions and binary-anion adsorption study. Phosphorus (Watanbe & Olsen 1965), boron (Hatcher and Wilcox, 1950), silicon (Jackson 1973), molybdenum (Ellis & Olsen 1950) were determined on spectronic 20 spectrophotometer. The amount of anion adsorbed was calculated from the difference between initial and final concentrations of anions in solution. The competitive adsorption of phosphate, silicate, molybdate and borate in binary mixtures with soils was studied by taking the varying concentration of one anion, while keeping the other constant, respectively. The multicomponent Freundlich type equation was applied to each binary-anion combination with soil. The general form of this model could be written for the adsorption of solute 'i' from binary-anion mixtures as : (x/m) i = K i C i (C i + a ij C j ) n i (i) and for the adsorption of anion 'j' from the binary mixture as (x/m) j = K j C j (C j + a ji C i ) n j (ii) Where (x/m) i is the amount of anion i adsorbed per mass of adsorbent in the presence of a competitive anion j, K i and K j are the single anion Freundlich constants for anion i and j, C i and C j are the equilibrium concentration of each anion, n i and n j are the single anion Freundlich exponents, a ij and a ji are the competitive coefficients. The competitive coefficients in equation (i) and (ii) is a positive value term that describes the extent of competitive interaction in a specific soil - anion system. Results and Discussion The adsorption of phosphorus, silicon, molybdenum and boron anions by Andretta silt loam and Haibowal silt loam were determined in monocomponent system and their respective 2

3 exponent and distribution coefficients are listed in Table 1. These coefficients were further employed to develop multicomponent Freundlich type equations. Table 1. Freundlich constants describing phosphorus, silicon and boron adsorption by Andretta silt loam (ph 4.2) and Haibowal silt loam (ph 8.0) at 298 o K Anion Andretta silt loam Haibowal silt loam K F n r2 SE K F n r2 SE Phosphorus Silicon Molybdenum Boron The multicomponent Freundlich type, i.e. Sheindorf - Rebhun - Sheintuch (SRS) equation (Sheindorf et al., 1981) was applied to examine the interaction of binary-anion mixture containing phosphorus - silicon, phosphorus - molybdenum, phosphorus - boron with Andretta silt loam and Haibowal silt loam soils. For each binary-anion system, a competitive coefficient was derived by a graphical approach developed by Sheindorf et al. (1981) A competitive coefficient for P-Si binary-anion system was formed for Andretta silt loam and Haibowal silt loam soils by plotting B p /C Si as the abcissa and C p /C Si as the ordinate, where K FP C P B p = Si (x/m) p n p and C P and C Si are the equilibrium concentrations of anion P and anion Si, respectively. The coefficient (a p - Si ) is the negative of the numerical value of the y-intercept as illustrated in fig 1. Similar method was used for calculating competitive coefficients for other binary-anion systems for both soils. All the 24 binary-anion systems in both soils were found to confirm to the SRS equation. The determined competitive coefficients were regarded as convenient single-valued terms that could be used to describe the degree of competition in the specific binary-anion soil system. The magnitude of phosphorus competitive effect on silicon adsorption was considerably more (a Si - P = 3.25) in acidic Andretta silt loam than in alkaline (a Si - P = 1.80) Haibowal silt loam 3

4 soil (Table 2). The magnitude of silicon's competitive effect on P adsorption was higher in alkaline Haibowal ailt loam (a p - Si = 1.10) than in acidic Andretta silt loam (a p - Si = 0.40). The competitive effect of P on the magnitude of Si adsorption was generally more than the competitive effect of Si on P anion adsorption in both, acid (a Si - p = 3.25 > a p - Si = 0.40) and alkaline (a Si - P = 1.80 > a p - Si = 1.10) soils. The competitive effect of Si on P anion adsorption was more in alkaline than in acidic (a p - Si = 1.10 > a p - Si = 0.40) soil. Similarly, Obihara and Russell (1972) reported that the presence of Si did not significantly affect the amount of P adosption below ph 6.4 in Woodburn clay loam. At higher ph Si significantly reduced the amount of P adsorbed. The competitive coefficients for adsorption of P and Mo anions from P-Mo binaryanionic mixtures were a p - Mo = 1.00 and a Mo - p = 1.20 in acidic Andretta silt loam and were a p - Mo = 0.52 and a Mo - p = 0.80 in alkaline Haibowal silt loam soils. In P-Mo anionic system, the competitive effect of P anion in reducing Mo adsorption was more than the competitive effect of Mo anion Table 2. Competitive coefficients for binary-solute system derived by Sheindrof - Rebhun - Sheintuch Freundlich type adsorption isotherm Anion Andretta silt loam Haibowal silt loam i j aij aji aij aji P + Si P + Mo P + B Si + Mo Si + B Mo + B in reducing P adsorption in both acidic (a Mo - p = 1.20 > a p - Mo = 1.10) and alkaline (a Mo - p = 0.80 > a p - Mo = 0.52) soils. Similarly, in both Polish soils, with increase in the amount of P adsorbed from P-Mo binary solution, there was reduction in the amounts of Mo adsorbed, in ph range of 4 to 8 (Gorlach et al., 1969). The reduction in Mo adsorption was maximum at ph 6.0 to 7.0. The results in the present experiments are also in agreement with Roy et al. (1986) that the adsorption of Mo by all three soils was significantly reduced with the presence of P, which was attributed to competitive interactions. In Haibowal silt loam, analogus and higher magnitude of competitive coefficients (a p - B = a B - P = 0.80) illustrated appreciably more and equivalent amount of P and B anions adsorption from P-B anionic mixtures under alkaline conditions. The presence of P in P-B system depressed 4

5 the adsorption of B, whereas B has negligible effect on the adsorption of P in acidic Andretta silt loam soil. This was due to decreased affinity of B anion for the adsorption siltes under acidic conditions. Below ph 7.0, B (OH) 3 predominate over B(OH) 4 ionic speciies in soil solution (Keren and Bingham, 1985). Since the affinity of clay and amorphous Fe ox and Al ox for B (OH) 3 species is relatively lower than B(OH) 4, the B adsorption is low in acidic soil. The presence of P in B-P mixtures competes with low concentration of B(OH) 4 anion at low ph and thus further depressed the amount of B adsorbed in Andretta silt loam soil. As the ph increased, the concentration of B (OH) 4 increased rapidly, but the concentration of H 2 PO 4 declined and thus eventually results higher B adsorption and lower P adsorption in alkaline Haibowal silt loam than Andretta silt loam soil. The competitive coefficients indicated similar effect of P and B on adsorption of each other in acidic Andretta silt loam and alkaline Haibowal loam soils. Similar results have also been reported by Bloesch et al. (1987) for B adsorption on goethite over the entire ph range of 5.2 to The competitive coefficients for Si-Mo binary-anion interaction with soil indicated that Mo anion appreciably reduced the amount of silicon adsorbed (a Si - Mo = 0.75 > a Mo - Si = 0.19) in acidic Andretta silt loam where as Si anion markedly depressed magnitude of Mo adsorption (a Mo - Si = 1.80 > a Si - Mo = 0.50) in alkaline Haibowal silt loam. Similarly, the adsorption of the Mo anion by some Australian soils was found to be maximum at ph 4.0, which is close to PK 2 value of molybdic acid and decreased with increase in ph. But the adsorption of Si anion by soils and related materials enhanced with increase in ph and maximum adsorption was recorded at ph 9.2 (Obihara and Russell, 1972). They suggested that hydroxylation of the surface at high ph values eventually favour the enhanced adsorption of Si (OH) 4 ion by soils and related materials. This shows that though the mechanism of Mo and Si anion adsorption is dissimilar yet these anions are competing for the same sorption sites on clay or hydrous oxide of iron and aluminium in both, acidic and alkaline soils. In an alkaline Si-B binary-anion system, the markedly higher and similar values of competitive coefficients (a Si - B = a B - Si = 0.60) illustrated appreciably more and equivalent amounts of Si and B adsorption in Haibowal silt loam. In acidic Si-B system, the low value of competitive coefficients (a Si - B = a B - Si = 0.15) showed that the amount of Si and B adsorption was low and the competitive effect of B on Si adsorption and Si on B adsorption in Andretta silt loam was analogus. The results obtained for the mono-anion adsorption of these anions also elucidated that the magnitude of Si and B adsorption was considerably more in alkaline Haibowal silt loam as compared to acidic Andretta silt loam soil. In B-Si binary-anion system, Goldberg and Glaubig (1988) found that B adsorption on alumina (Al 2 O 3.nH 2 O) was significantly reduced by the presence of added silicon. However, the amount of silicon adsorbed was much greater in B-Si anionic mixture by alumina than the reduction in boron adsorption. They concluded that majority of these anion occurs on sites preferential to one of the anions. But the competitive coefficients in present experiment with both the soils indicated that Si and B 5

6 anion does compete for the same adsorption sites, nevertheless the mechanism of adsorption for these anion could differ with ph and nature of their ionic species. The competitive effect of B (a Mo - B = 1.00) in Mo-B system, markedly depressed the amount of Mo anion adsorption in alkaline Haibowal silt loam. The higher competitive effect of B on Mo adsorption was due to increased amount of B adsorption accompanied with decline in Mo adsorption under alkaline condition for Haibowal silt oam soil. The competitive effect of Mo on B anion adsorption was higher (a B - Mo = 0.20) than the competitive effect of B on Mo anion adsorption (a Mo - B = 0.10) in acidic Andretta silt loam. The stronger competitive effect of Mo anion under acidic condition was due to enhanced magnitude of Mo adsorption alongwith simultaneous reduction in B adsorption. Similar results have also been observed in the present investigation for mono-anion adsorption studies in acidic and alkaline soils. References Bloesch, P.M., L.C. Bell and J.D. Hughes Adsorption and desorption of boron by Goethite. Aust. J. Soil Res. 25: Ellis, R. and R.V. Olsen Photometric determination of molybdenum by acetone reduction of thiocyanide. Anal. Chem. 22: Goldberg, S. and H.S. Forster Boron sorption and calcareous soils and reference calcite. Soil Sci. 152: Gorlach, E., K. Gorlach and A. Compala The effect of phosphate on the sorption of molybdate in the soil. Agrochimica 13: Hatcher, J.T. and L.V. Wilcox Colorimetric determination of boron using carmine. Anal. Chem. 22: Jackson, M.L Soil Chemical Analysis - Advance Course, Department of Soil Science, Univ. of Wisconsin, Madison Keren, R., and F.T. Bingham Boron in water, soil and plants. Adv. Soil Sci. 1: Obihara, C.H. and E.W. Russell Specific adsorption of silicate and phosphate by soils. J. Soil Sci. 23: Roy, W.R., J.J. Harsett and R.A. Griffin Competitive coefficients for the adsorption of arsenate, molybdate and phosphate mixtures by soils. Soil Sci. Am. J. 50;

7 Sheindorf, C.H., M. Rebhun and M. Sheintuch A Freundlich multicomponent isotherm. J. Colloid and Interf. 79: Watanabe, F.S. and S.R. Olsen Test of an ascorbic acid method for determining phosphorus in water and NaHCO 3 extractants. Soil Sci. Soc. Am. Proc. 29: Keywords : adsorption, phosphate, Freundlich isotherm, inorganic anions Mots clés : adsorption, phosphate, isotherme de type Freundlich, anions minéraux 7

8 Fig. 1. Phosphorus adsorption by (a) Andretta silt loam and (b) Haibowal silt loam soil in the presence of silicate anion. 8

Boron Adsorption by Some Semi-Arid Soils of North Eastern Nigeria

International Journal of Applied Agricultural Research ISSN 0973-2683 Volume 6 Number 1 (2011) pp. 71 76 Research India Publications http://www.ripublication.com/ijaar.htm Boron Adsorption by Some Semi-Arid