Polymer Type and Water Quality Effects on Soil Dispersion
- Awad M. Helalia and
- J. Letey
Ten polyacrylamide (PAM) and derivatized guar compounds, with different charges were tested at 0, 10, and 50 mg L−1 concentration with low electrolyte solution (1 molc m−3) at 0, 5, and 20 sodium absorption ratio values for their ability to reduce dispersion of three soils. Dispersion was determined by measuring the soil settling rate in solution. All compounds were effective in promoting clay flocculation at a concentration of 10 mg L−1. When compared at comparable charge, the PAM compounds were more effective than the guar compounds. This result is consistent with their higher molecular weight. The order of effectiveness of the compounds was cationic > nonionic > anionic. No cationic PAM compounds were available and the cationic guar compound (CP-14) was comparable to the nonionic PAM. Flocculation decreased very slightly as the SAR increased, suggesting that the effect of low electrolyte concentration was the prominent factor in dispersion. The cationic guar “CP-14” was tested separately with low (0.05 dS m−1) and moderate (0.7 dS m−1) electrolyte concentrations simulating canal and well waters from California. Its effect on flocculation was very high at 5 mg L−1 concentration in both waters after only 10-min settling. Increasing the concentration >10 mg L−1 did not improve the flocculation results.
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