Effect of particle size on resistance to chloride for hydrodechlorination of trichloroethylene in water

Karahan, Selin
Contamination of groundwater by chlorinated compounds is an important environmental hazard to humanity because worldwide drinking water demand is generally supplied by groundwater. Chlorinated pollutants, especially trichlorethylene (TCE), are released to the environment due to its frequent use in industrial applications. This highly toxic chemical poses a serious threat to human health and the environment. In this regard, cleaning of groundwater from TCE is of great importance. Catalytic hydrodechlorination (HDC) is a desirable approach for remediation of water contaminated with chlorinated compounds. It is an elimination-based catalytic remediation technique where toxic chlorinated compounds in water are transformed to chloride-free hydrocarbons with hydrogen over a catalyst. Studies conducted so far have concluded that platinum (Pt) and palladium (Pd)-based catalysts show high catalytic activity for HDC of chlorinated compounds. However, during HDC, the overall performance of the catalyst is mainly affected by (i) adsorption of the reactants and the reaction medium on catalyst surface, (ii) simultaneous reactions including dechlorination, hydrogenation, and hydrodechlorination, and (iii) inhibition due to the unavoidable reaction product HCl. Of particular note is the inability of HCl to desorb from the active sites that leads to complete loss of the catalytic activity and irreversible catalyst deactivation by the chloride poisoning. This effect, however, could be alleviated by catalysis engineering. In this study, the objective is to undertake an approach to investigate the effect of particle size of Pt nanoparticles (Pt NPs) on resistance to chloride poisoning for HDC of TCE in water. Although there are existing studies which examined particle size effect on catalytic activity, studies on HCl inhibition are scarce. By fine-tuning the particle size distribution of catalysts, the inhibition problem of HDC catalysts can be circumvented. The study includes synthesizing Pt nanoparticles with three different particle sizes (3.0, 5.8 and 60.9 nm) by colloidal synthesis method, performing activity experiments in a semi-batch reactor, carrying out characterization studies and performing kinetic measurements. The results demonstrate that Pt NPs were synthesized successfully as evidenced by transmission electron microscopy. For 20 ppm initial TCE concentration, almost 100% conversion was achieved in all experiments. As expected, the fastest reaction kinetic was observed at the smallest particle size. Rate constants were found as 4.2 h-1, 1.3 h-1 and 0.4 h-1 for Particle size 1 (small), 2 (medium) and 3 (large), respectively. The initial turnover frequency (TOF) was calculated based on initial rate and molar concentration of Pt in the batch reactor. TOF data (0.077 (Particle 1), 0.023 (Particle 2) and 0.007 (Particle 3) mol TCE/(mol Pt.s)) decreased with increasing particle size. The highest resistance to chloride poisoning were also observed at the smallest particle size. The heat and mass transfer limitations were also investigated. Kinetic experiments performed within the scope of this study revealed insight into structure sensitivity of reactions involved in HDC of TCE in water at atmospheric conditions.


Qualitative evaluations about the disinfection capabilities of a water distribution network : a model study
Nadiroğlu, Coşkun; Köken, Mete; Aydın, İsmail; Department of Civil Engineering (2014)
“Chlorine” is one of the major disinfectants extensively used in distribution systems that neutralizes the disease-causing organisms. This model study evaluates the disinfection capabilities of a specific water distribution network N8.3 of Ankara water distribution system under various operating conditions. N8.3 supplies water, roughly to 40,000 people. The network is served by a pump station and pumping schedule is critical concerning the occurrence of minimum chlorine concentrations. Continuous “blind” pu...
Influence of system parameters on the disinfection capability of water distribution networks /
Koç, Selin; Merzi, Nuri; Department of Civil Engineering (2014)
Adequate municipal water supply for people, is one of the most important signs of civilization. When water is cleaned from unhealthy compounds, the most important point for consumers is completed. Chlorine is used as the most common disinfectant. Some basic parameters which affect water quality are roughness coefficient, wall decay coefficient and bulk decay coefficient; amount of leakage is also effective. Efficiency of the network and water quality are influenced by changing these parameters in a water di...
Performance of ozone and peroxone on the removal of endocrine disrupting chemicals (EDCs) coupled with cost analysis
Ölmez Hancı, Tuğba; Dogruel, S.; Emek, A. D. Allar; Yilmazer, C. Eropak; Cinar, S.; Kiraz, O.; Citil, E.; Orhon, A. Koc; Siltu, E.; Gucver, S. M.; Ozgun, O. Karahan; Tanık, Ayşe Gül; Yetiş, Ülkü (IWA Publishing, 2020-08-01)
Micropollutants such as endocrine disruptors are one of the most important groups of chemicals polluting water resources. Conventional treatment systems may not be effective for the removal of endocrine disrupting chemicals (EDCs), and the fate of these chemicals should be carefully monitored in the effluent of wastewater treatment plants (WWTPs). Additional treatment methods such as advanced oxidation processes can be used for the removal of endocrine disruptors. This study presents the existence of endocr...
Chance constrained optimization of booster disinfection in water distribution networks
Köker, Ezgi; Altan Sakarya, Ayşe Burcu; Department of Civil Engineering (2011)
Quality of municipal water is sustained by addition of disinfectant, generally chlorine, to the water distribution network. Because of health problems, chlorine concentration in the network is limited between maximum and minimum limits. Cancerogenic disinfectant by-products start to occur at high concentrations so it is desired to have minimum amount of chlorine without violating the limit. In addition to the health issues, minimum injection amount is favorable concerning cost. Hence, an optimization model ...
Effect of drainage properties on seepage behavior of earth fill dams
Çalamak, Melih; Yanmaz, Ali Melih (2016-09-23)
Earth-fill dams should be designed in such a way that excessive pore water pressures and seepage are controlled for attaining the desired safety level. This type of dams can be supplemented by some drainage facilities, such as blanket and chimney drains, which are commonly composed of graded soils. The key issue in designing a drainage facility is to promote the effectiveness of the system in reducing the pore water pressures and the seepage quantity. The performance of the drainage facility is based on its...
Citation Formats
S. Karahan, “Effect of particle size on resistance to chloride for hydrodechlorination of trichloroethylene in water,” M.S. - Master of Science, Middle East Technical University, 2022.