The aim of this study is the development and characterization of a carbon-based electrochemical sensor, modified with TiO2 nanoparticles for potential application in electroanalytical techniques. The influence of binder and modifier contents on morphological, physicochemical and electrochemical characteristics of the electrode material was investigated in order to determine the optimal ratio of the carbon material/binder/modifier. Carbon pastes were prepared from mixtures containing graphite powder, TiO2 nanoparticles and liquid hydrocarbons. Scanning electron microscopy showed that the electrode material becomes more compact with the addition and the increase in the binder material content, while increasing the proportion of TiO2 nanoparticles did not have any significant effect on the material morphology showing fairly homogeneous nanoparticle distribution in the graphite electrode material. The test results indicate that the modified carbon paste with 40 vol.% paraffin oil (PO) and 6-8 wt.% TiO2 nanoparticles is characterized by the lowest value of specific resistance. By applying cyclic voltammetry, the most pronounced degree of reversibility was obtained in relation to the standard reversible redox system ([Fe (CN)]-3/-4) for the electrode material with 30-40 vol.% PO and 8-10 wt.% TiO2 nanoparticles. Characterization of the electrode material based on carbon modified with TiO2 nanoparticles indicated that the optimal composition contains 40 vol.% PO and 6-8 wt.% TiO2 nanoparticles, which is important for application in electroanalytical techniques.

Phenolic pollutants raise health and environmental concerns due to their widespread occurrence in industrial wastewaters. Electrooxidation was studied for phenol degradation in different supporting electrolytes: NaCl, Na2SO4, H2SO4. Experiments were performed at constant current density 20 mA/cm2. Two anode materials were tested, boron-doped diamond (BDD) and mixed-metal oxide (MMO). Degradation process and its impact was investigated from technological, analytical, and ecotoxicological viewpoints. Removal efficiency was monitored by phenol index spectrophotometric method and phenol removal quantified with HPLC-DAD. Additionally, transformation by-products were tracked with GC-MS and LC-MS, as well as ion chromatography. Finally, ecotoxicity was investigated using Daphnia magna. Electrooxidation was efficient and had low energy consumption. The use of BDD anode led to higher removal efficiencies and induced more progressive degradation to simple organic acids, compared to MMO. Selection of electrolyte affected degradation pathways and detoxification pattern. Treatment by BDD in NaCl led to complete phenol removal in 30 min, but undesired chlorinated aromatic by-products were formed. Treatment in sulphate medium led to slower processes irrespective of pH, but less problematic by-products with minimal ecotoxicological impact emerged. By using multi-aspect methodology, this study reevaluates phenol electrooxidative degradation and contributes to better understanding of electrooxidation performance in water treatment.

Phenolic compounds are widespread in wastewater from various industries. Since the phenols are potentially carcinogenic for humans and hazardous for the environment, their presence in wastewater raises concerns. In this paper electrooxidation process was used for treatment of synthetical prepared wastewater containing phenol. Initial phenol concentration in wastewater was 50 mg/L with addition of different supporting electrolytes (NaCl, Na2SO4, H2SO4). The treatment was performed in a batch electrochemical reactor at constant current density of 20 mA/cm2. Boron doped diamond (BDD) and mixed metal oxide (MMO) anode materials were examined, and stainless steel was used as cathode. Phenol concentration before and after treatment was determined by standard spectrophotometric method with 4-aminoantipyrine, while transformation products were identified by different chromatographic methods. Experiments have shown that the treatment is very efficient and with low energy consumption, wherein the phenol removal efficiency mostly depends on the duration of treatment and the type of supporting electrolyte.