Adsorption of surfactants on Saudi Arabian limestone.
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Saudi Digital Library
Abstract
Static adsorption experiments were conducted to investigate the adsorption and precipitation properties of various surfactants including petroleum sulfonate (TRS10-410), ethoxylated sulfonates (v2880, v3348, B1083, B1139) and nonionics (T150) onto Saudi Arabian limestone. The effect of parameters such as solid to liquid ratio, salinity, pH, temperature, surfactant type, ethoxylation number, sacrificial agents, oil and alcohol has been investigated. The adsorption data for limestone/TRS10-410 system and v2880/system at different salinities show that the increase in ionic strength generally increases the surfactant adsorption on limestone at higher sulfonate concentrations. The dependence of adsorption on pH shows marginal sulfonate adsorption above ZPC (pH=8.3) where limestone is negatively charged and extremely high adsorption below pH of 8.3, where the surface of limestone acquires positive charge. Temperature data at three different levels (25, 50 and 90 degree C) show that adsorption drastically increases with increasing temperature. Increasing the ethoxylation number of surfactants decreases the adsorption but concurrently increases the CMC of surfactants. The results also indicate that adsorption of surfactants on limestone can be reduced with addition of silicates as sacrificial agents and n-butanol as co-surfactant. Adsorption data in the presence of crude oil show that adsorption of ethoxylated sulfonates increases significantly in the oil. The adsorption tests for nonionics (T150) show about five-fold higher adsorption than the anionic surfactant (B1083) of the same ethoxylation number under the same experimental conditions. Precipitation behavior of TRS10-410 in the presence of NaCI and CaCl2 indicates that the surfactant is not tolerant to even as low as 1% NaCl and 0.15