Organic additives and electrolytes as cloud point modifiers in octylphenol ethoxylate solutions

Cloud point measurements of nonionic surfactant Triton X-100, an octylphenol ethoxylate, were carried out in the absence and presence of various organic additives such as n-alkanols (methanol, ethanol, propanol and butanol), glycols (ethylene glycol, diethylene glycol and triethylene glycol), glycol ethers (ethylene glycol monomethyl ether, ethylene glycol monoethyl ether and ethylene glycol monobutyl ether (EGMBE)) and electrolytes (LiCl, KCl, NaF, NaCl, NaBr, NaI, MgCl2 and AlCl3). The combined effect of these organic additives and electrolytes on cloud point (CP) measurement was also investigated. The effect of nature of cation, anion and valency of cation on CP is also reported. Among the n-alkanols and glycol ethers as additives, n-butanol and EGMBE were found to decrease the CP while all other additives increase the cloud point. The addition of electrolytes (LiCl, NaCl and KCl) to the solution of Triton X-100 (TX-100) decreases the CP but the rate of decrease in CP with concentration does not follow the lyotropic series of effect. Sodium halides (except NaI) also decrease the CP and the rate of decrease follows the lyotropic series of effect even in the presence of organic additives. NaI is a water structure breaker, hence it increases the cloud point. Further, cations of increasing valency lessen the depression in CP of TX-100 with the rate of decrease in CP following the order Na+ > Mg2+ > Al3+ even in the presence of organic additives.