INFLUENCE OF NITRATES, PHOSPHATE, SULPHATE AND SALTS OF Ca, Mg AND K, ON HYDROGEL HYDRATATION CAPACITY

ABSTRACT Hydrogel hydration capacity in solution was evaluated at different levels of electrical conductivity (EC) using nitrate, phosphates, sulfates, and salts of calcium, potassium and magnesium. Four sequential experiments were performed using potassium polyacrylate copolymer. The first experiment aimed to determine the lowest hydrogel dose, at which occur maximum deionized water absorption. The test was assembled in a completely randomized design with six hydrogel doses (1, 2, 4, 6, 8 and 10 g L-1) and four replicates. The second experiment consisted of testing the sucrose P.A. doses (0, 1, 2, 4 and 6 %) in order to evaluate the change in osmotic potential of the solution on hydrogel hydration. The third and fourth studies were carried out in a complete randomized design, using a 6 x 3 x 2 factorial scheme with four replicates. For the third experiment, the factors were six levels of EC (0; 0.25; 0.50; 1.00; 1.50 and 2.00 mS cm1) increased by the addition of three anions (NO3-; PO43- and SO42-) along with counter-ions Ca++ and K+. For the fourth experiment, the same six levels of EC were achieved by adding the three cations (Ca++, Mg++ and K+), along with the counter-ions Cl- and SO42-. Hydration capacity of the hydrogel decreases when the ionic concentration of the solution increases and the reduction of the osmotic potential through the addition of sucrose does not interfere in its swelling capability. Anions and cations in the solution negatively influence the process of the hydrogel hydration. The most pronounced effect is for those with higher valence.

摘要：本研究以硝酸根、磷酸根、硫酸根及钙、钾、镁盐类为溶质，评估了不同电导率（Electrical Conductivity，EC）条件下水凝胶在溶液中的溶胀持水能力。本研究采用聚丙烯酸钾共聚物开展了四组连续实验。第一组实验旨在确定可使水凝胶达到去离子水最大吸附量的最低水凝胶投加量。该实验采用完全随机设计，设置6个水凝胶投加梯度（1、2、4、6、8、10 g·L⁻¹），每组设置4次重复。第二组实验通过设置不同分析纯蔗糖投加梯度（0、1、2、4、6%），探究溶液渗透势变化对水凝胶溶胀行为的影响。第三、第四组实验均采用完全随机设计，设置6×3×2因子实验方案，每组设置4次重复。第三组实验的因子包括6个电导率梯度（0、0.25、0.50、1.00、1.50、2.00 mS·cm⁻¹），通过添加三种阴离子（NO₃⁻、PO₄³⁻、SO₄²⁻）分别与反离子Ca²⁺、K⁺复配实现。第四组实验则通过添加三种阳离子（Ca²⁺、Mg²⁺、K⁺）分别与反离子Cl⁻、SO₄²⁻复配，得到与第三组一致的6个电导率梯度。实验结果表明，水凝胶的持水溶胀能力随溶液离子浓度升高而降低；而通过添加蔗糖降低溶液渗透势，并不会对其溶胀性能产生影响。溶液中的阴离子与阳离子均会对水凝胶的溶胀过程产生负面影响，其中价态更高的离子抑制效果更为显著。