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Effect of pH on adsorption and desorption of hexadecyl trimethyl ammonium bromide from silicate surface

Karaguzel C., Xu Z.

Physicochemical Problems of Mineral Processing

2017

Vol. 53, iss. 2

750--757

Hexadecyl trimethyl ammonium bromide (HTAB), a cationic surfactant, is physically adsorbed on negatively charged silicate surfaces due to electrostatic forces. This reversible adsorption process is important for surfactant regeneration in some industrial applications such as waste water treatment. Cationic surfactant adsorption and desorption from silica surfaces were studied using several methods such as UV, FTIR, XPS, and XRD. However, most of these methods are time independent and ex situ in nature. Quartz crystal microbalance with dissipation monitoring (QCM-D) is a power tool that can determine the amount and thickness of the deposited material on the surface in situ as a function of time. In this study, the adsorption and desorption characteristic of HTAB was studied on the silica sensor surface by using QCM-D. The adsorption and desorption tests were performed at a constant HTAB concentration (5·10-4 M, close to CMC of HTAB) at different pH values (3, 5.5, 6.5 and 10). The results obtained from these studies clearly showed that pH is a critical factor determining the adsorption and desorption processes.

The effect of zeta potential on the sedimentation behavior of natural stone processing effluent

Kurama H., Karaguzel C.

Physicochemical Problems of Mineral Processing

2013

Vol. 49, iss. 2

575--586

One of the main problems for the natural stone industry is treatment of huge amount of waste sludge resulting from the cutting and polishing of them to produce slabs or tiles. The effective treatment of this sludge is very important for reducing of the sludge volume and overall operating costs. Previous studies showed that settling rate and water clarity of the supernatant solution can be increased by flocculation process. In this study, detailed electrokinetic studies were performed on the travertine samples received as natural and slurry form. The natural form of the sample was supplied from a travertine quarry while the slurry was taken from the cutting and polishing process wastewater collector pool of the processing plant. The electrokinetic measurements were conducted to find out the effect of suspension pH and the solid content on the surface potential of solid particles show that zeta potential (ζ) of travertine is positive at pH 9.76 over the all solid contents studied in this work. However, ζ of the particles become negative at lower pH values for 1% solid weight content. In contrast, for travertine slurry (6.73% solid weight), different potential variations were determined. The particles were negatively charged between pH 6 and 8. The results highlighted the effect of dissolved specific ions in the waste slurry and sensitivity of ζ to the ionic strength of the solution. The ζ measurements for a raw travertine sample, performed with different amounts of NaCl additions into the solutions, confirmed the above findings. An addition of low amounts of NaCl decreases ζ of the solid surface. Finally, the ζ measurements in the presence of polymer concentration of 0.001% to 0.1 % (wt/vol) clearly indicated that the flocculant molecules are adsorbed extensively on the travertine particles, and increase the surface potential of the particles with increasing reagent concentration.