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、镁盐为溶质，考察不同电导率（EC）溶液中水凝胶（Hydrogel）的水合容量。采用聚丙烯酸钾共聚物开展四组序贯实验。
第一组实验旨在确定使去离子水吸附量达到最大值的最低水凝胶用量。实验采用完全随机设计，设置6个水凝胶剂量梯度（1、2、4、6、8、10 g·L⁻¹），每组设置4次重复。
第二组实验设置分析纯（P.A.）蔗糖剂量梯度（0、1、2、4、6%），以考察溶液渗透势变化对水凝胶溶胀行为的影响。
第三组与第四组实验采用完全随机设计，设置6×3×2因子设计方案，每组设置4次重复。其中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3种阴离子（NO₃⁻、PO₄³⁻、SO₄²⁻）及对应的抗衡离子Ca²⁺与K⁺得到；第四组实验则通过添加3种阳离子（Ca²⁺、Mg²⁺、K⁺）及对应的抗衡离子Cl⁻与SO₄²⁻来实现相同的6个电导率梯度。
实验结果显示：溶液离子浓度升高会降低水凝胶的水合容量；通过添加蔗糖降低溶液渗透势并不会对其溶胀能力产生干扰。溶液中的阴离子与阳离子均会对水凝胶吸水过程产生负向影响，其中价态更高的离子其抑制效果更为显著。