Bahri Ersoy

Electrokinetic properties of clinoptilolite with mono- and multivalent electrolytes

In this study, electrokinetic properties of clinoptilolite have been determined. A series of systematic zeta potential measurements have been performed to determine the isoelectric point (iep) and potential determining ions (pdi), and the effect of mono- and multivalent salts such as NH4Cl, CaCl2, Al(NO3)3 on the zeta potential of clinoptilolite. Clinoptilolite in water exhibits a negative surface charge and maintains this character even in very acidic conditions of pH 2–3. This reveals that clinoptilolite has no iep in the pH range of 2–12. H+ and OH− ions are the pdi for clinoptilolite. Excluding the trivalent Al3+ cations, monovalent and divalent cations are not able to reverse the surface sign of clinoptilolite. This is attributed to the ion exchange ability of clinoptilolite and the strong specific adsorption of the Al3+ counterions. A schematic adsorption model which accounts for the adsorption of mono- and multivalent ions in the electrical double layer of clinoptilolite is proposed.

EFFECT OF HYDROCARBON CHAIN LENGTH ON ADSORPTION OF CATIONIC SURFACTANTS ONTO CLINOPTILOLITE

The adsorption behavior of quaternary ammonium cationic surfactants with different hydrocarbon chain lengths, i.e. HDTMA (hexadecyltrimethylammonium), TDTMA (tetradecyltrimethylammonium) and DDTMA (dodecyltrimethylammonium), onto clinoptilolite has been investigated. The adsorption isotherms of these surfactants are correlated with the ζ potential curves of clinoptilolite. Accordingly, the applicability of the hemimicelle hypothesis to the adsorption of cationic surfactants at the clinoptilolite/water interface considering in the electrical double layer (EDL) of clinoptilolite is discussed. Even though the adsorption occurs in the EDL of clinoptilolite, the adsorption of HDTMA, TDTMA and DDTMA onto clinoptilolite is not conveniently described by the hemimicelle hypothesis. The absence of all expected marked increase in the ζ potential curves at the hemimicelle concentration is ascribed to the large external cation exchange capacity of clinoptilolite. The hydrocarbon chain length of surfactant molecules is found to have a significant effect on the ion exchange as well as hydrophobic interaction mechanisms. The effectiveness of both ion exchange and hydrophobic interactions increases with increasing chain length, and so the greatest surfactant adsorption onto clinoptilolite was obtained by HDTMA.

Uptake of aniline and nitrobenzene from aqueous solution by organo‐Zeolite

Abstract Adsorption mechanisms of toxic non‐ionic organic contaminants (NOCs), aniline and nitrobenzene, with natural‐zeolite and organo‐zeolite (OZ) were investigated in both batch and continuous systems. In batch tests, the adsorption capacity of aniline and nitrobenzene onto natural zeolite surface is very low or almost nil but becomes significant upon modifying the zeolite surface by hexadecyltrimethylammonium (HDTMA). A partitioning mechanism is proposed to be responsible for the adsorption of NOCs onto OZ. The effectiveness of the partitioning mechanism is directly connected with hydrophobic properties of the NOCs. The column tests were carried out as an indicator for continuous system. The breakthrough curves were constructed for OZ/NOC system and the adsorption capacity of NOCs onto OZ under the present conditions were determined as 2.36 and 325 mg per gram of OZ, for aniline and nitrobenzene, respectively. A schematic model is proposed to account for the adsorption of NOCs onto OZ.

Effect of mixing water types on the time-dependent zeta potential of Portland cement paste

Abstract The measurement of zeta potential (ZP) has important applications in a wide range of industries including ceramics, pharmaceuticals, medicine, mineral processing, electronics, cement industry and water treatment. It provides new information on cement hydration, gel structure formation and the effects of chemical and mineral admixtures. In this study, ZP and pH measurements of Portland cement suspension prepared at wt% 1 cement/water ratio in the presence of four different types of waters, i.e., pure water, tap water, and salted (NaCl and CaCl2) water, were carried out depending on the time. Also, vicat tests of Portland cement pastes prepared at a water-to-cement ratio of 0.34 were performed. After the vicat tests, X-ray diffraction analysis and scanning electron microscopy investigations were performed on the samples. The most important result obtained from this study is that setting time and time-dependent ZP values of Portland cement paste have different values depending on the used mixing water type. Among the water types, water with CaCl2 gives the lowest ZP as absolute value, so this leads to minimum initial and final setting times for the cement paste prepared with this type of water.

Novel functional copolymers based on glycidyl methacrylate: Synthesis, characterization, and polymerization kinetics

ABSTRACT A new methacrylate monomer 2-(4-nitrophenyl)-2-oxoethyl-2-methacrylate (NFM) was synthesized and its radical copolymerization with glycidyl methacrylate (GMA) was studied in 1,4-dioxane solution at 65°C using 2,2′-azobisisobutyronitrile as an initiator. The synthesized monomer and copolymers were characterized by FTIR, 1H and 13C-NMR spectroscopy. The analysis of reactivity ratios revealed that NFM is less reactive than GMA, and copolymers formed are statistically in nature. Thermogravimetric analysis of the polymers reveals that the thermal stability of the copolymers increases with an increasing in the mole fraction of NFM in the copolymers. Glass transition temperatures of the copolymers decreased with an increasing of NFM molar fraction in copolymers. In addition, according to the results obtained from the contact angle and zeta potential measurements the hydrophobic character of the polymer decreases (it means surface free energy increases) and its zeta potential becomes more negative with increase of NFM ratio in the copolymer. Polymers with carbonyl functional groups have been particularly interesting because of their use as photoresists.

Preparation and Characterization of Sol-Gel Derived 4%La2 O3-Al2O3 Ceramic Membrane on Clay-Based Supports

In this work, γ-Al 2O3 membrane layer (4 wt % La 2O3 + 96 % Al 2O3 ) was coated on the clay based porous support by using the sol-gel coating. The coating solution was prepared by using boehmite (AlOOH), La-nitrate (La 2(NO 3)3.6H 2O), PVA, distilled water and HNO 3. The thickness of the γ-Al 2O3 membrane layer was between 5-7 μm. Two unprocessed clay samples which were supplied from Kutahya and Balokesir regions, were used to produce supports for the membranes. Porosities of the supports were varied from 25 to 40% depending on sintering temperatures. Mean pore diameter of the supports were between 0.01-1μm. The mean pore diameter of 4wt%La 2O3 - Al 2O3 membrane layer was around 11 nm and total pore area was 113 m 2 / g at 1000 0 C for 1 hour.