Abstract:

Using Cu²⁺ as a probe, the chelation of Cu²⁺ with trisodium methylglycine diacetate （MGDA） was tested by infrared spectroscopy in presence of different surfactants such as sodium fatty alcohol polyoxyethylene ether carboxylate （AEC-9Na）, sodium dodecyl diphenyl ether disulfonate （2A1）, iso-alkyl glycoside （IC-06）, fatty alcohol polyoxyethylene ether （AEO9）, cocamidopropyl betaine （CAB）, and cocamidopropyl amine oxide （CAO）. The apparent salt tolerance and system stability of these six surfactants in presence of MGDA were evaluated by light transmittance. The effects of MGDA on the application properties of the six surfactants were studied on a surface tensiometer, a contact angle tester and a foam analyzer. The results showed that the addition of surfactants promoted the chelation of MGDA to Cu²⁺. All these six surfactants had good salt resistance, among which 2A1 and CAB had the strongest salt resistance, which could reach 50% and 30%, respectively. The stronger the hydrophilicity of the surfactant, the better the salt tolerance. The addition of MGDA had sightly good effects on the surface activity of surfactants. The addition of MGDA improved the wetting ability of surfactants. Under the condition of constant surfactant concentration, the contact angle decreased with the increase of MGDA concentration. The addition of MGDA improved the foaming properties of the surfactants, and the foaming was faster. All the six surfactants showed good foam stability within 300 s. The effects of surfactants on MGDA chelation were investigated by light transmittance. The results showed that 2A1 and CAB had the strongest promoting effect on Cu²⁺ removal.

Key words: Cu²⁺, trisodium methylglycine diacetate, surfactant, chelation, wetting, foam