Adsorption of diclofenac onto organoclays: Effects of surfactant and environmental (pH and temperature) conditions

TLDR: The thermodynamic parameters derived from the fitting procedure point out the strong electrostatic interaction with organic cations adsorbed within the interlayer space in the organoclays for the adsorption of diclofenac.

About: This article is published in Journal of Hazardous Materials.The article was published on 2017-02-05 and is currently open access. It has received 129 citations till now. The article focuses on the topics: Freundlich equation & Adsorption.

Figures

Fig. 1. (a) XRD patterns for dehydrated Na-Mt, BDTA-Mt and HDTMA-Mt organoclays. (b) FTIR spectra of Na-Mt, BDTA-Mt and HDTMA-Mt organoclays. The proper intercalation of both surfactants is confirmed by the shift of the first 00l reflection at low angle values (XRD data) and with the CH2 scissoring and stretching bands of the alkyl tails of the organic cations.

Fig. 4. Evolution of normalized integrated FTIR intensity of both CO2 - bands (diclofenac) and CH2 bands (surfactants) as a function of the starting diclofenac concentration. The lines are guides for the eyes.

Fig. 7. Equilibrium adsorption isotherms of diclofenac (pKa=4.51) onto HDTMA-Mt organoclay (prepared at a concentration of 4 times the CEC of the starting Mt) for three different pH values of 3.5, 6.0-6.5, and 11.0. The efficiency of the adsorption is enhanced at high pH.

Fig. 3. 3D evolution of the FTIR spectra in the wavenumbers window of CH2 stretching bands for (a) HDTMA-Mt organoclay in the range 2800-3000 cm -1 and the (b) CO2 - stretching bands of diclofenac in the range 1450-1650 cm -1 for different starting diclofenac concentrations (0.1, 0.4, 0.6, 1 and 2 g L -1 ).

Fig. 2. Effect of the chemical nature of cationic surfactant (BDTA-Mt and HDTMA-Mt) on adsorption of diclofenac at ambient temperature (25°C) and using starting concentration of diclofenac ranging from 10 mg L -1 to 2 g L -1 .

Fig. 6. Equilibrium adsorption isotherms of diclofenac onto BDTA-Mt organoclay (prepared at a concentration of 4 times the CEC of the starting Mt) for 4 different temperatures: 5, 25, 35, 50°C. The efficiency of the adsorption is greater at low temperature.