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Nonylphenol ethoxylate (NPE 10) is a non ionic surfactant which is synthesized from alkylphenol ethoxylate. The accumulation of NPE-10 in wastewater will endanger the ecosystem as well as human being. At present, by an advancement of technology NPE 10 can be degraded indirectly by using an electrochemically treatment. Thus, this study aimed to evaluate the potential electrodegradation of NPE 10 by mediated electrochemical oxidation (MEO) using Ce(IV) ionic mediator. In addition, the influence of Ag(I) ionic catalyst in the performance of MEO for degradation of NPE 10 was also observed. The potency of MEO technology in degradation NPE 10 was evaluated by voltammetry technique and confirmed by titrimetry and LC-MS analyses. The results showed that in the absence of Ag(I) ionic catalyst, the degradation of NPE 10 by MEO was 85.93 %. Furthermore, when the Ag(I) ionic catalyst was applied, the performance of MEO in degradation of NPE 10 was improved to 95.12 %. The back titration using Ba(OH)2 confirmed the formation of CO2 by 46.79 %. Whereas the redox titration shows the total of degradation organic compounds by 42.50 %, which was emphasized by formation of two new peaks in LC-MS chromatogram. In summary, our results confirm the potential of MEO technology for NPE-10 degradation., Comment: 22 pages, 8 figures

Selenium is one of the heavy metal pollutants in the aquatic environment. Selenite is a form of inorganic selenium, which is very poisonous to living things. Therefore, we need a method that selectively identify selenite to determine its concentration in water. In this study, a square wave stripping voltammetry was used to measure selenite concentration using copper amalgam working electrode. The optimum measurement parameters were obtained at a deposition potential of –450 mV and a deposition time of 800 seconds. This analysis method had good precision with a relative standard deviation (% RSD) of 4.89%. Linear calibration curves are shown in the range 0.03 mM – 0.10 mM with R2 of 0.988 and in the range of 0.10 mM – 0.70 mM with R2 of 0.995 and a detection limit of 9.0 µM. The standard selenite solution was measured with a recovery percentage of 96.67%. The same solution was measured using the HG-AAS method and the recovery percentage was 96.35%. Statistical tests using the t-test showed that the two results did not have a significant difference with a 95% confidence limit. Thus, the voltammetry method using copper amalgam working electrode can be used as an alternative method for determining selenite, as it is cheaper and simpler than the HG-AAS method.

Pada penelitian ini dikembangkan suatu metode pengukuran Cr(III) menggunakan elektroda pasta karbon (EPK) yang termodifikasi EDTA yang dapat diaplikasikan dalam penentuan efektivitas reduksi limbah Cr(VI) serta penentuan Cr(VI) dalam suatu sampel secara tidak langsung. Metode analisis voltammetri yang dilakukan menggunakan teknik voltammetri siklik, differential pulse voltammetry dan square wave voltammetry. EDTA merupakan ligan polidentat yang dapat mengkelat beberapa logam. Untuk logam kromium, EDTA hanya bisa mengkelat Cr(III). Oleh karena itu, dalam proses pengukurannya dilakukan reduksi Cr(VI) menjadi Cr(III) yang kemudian dapat dianalisis menggunakan EPK yang termodifikasi EDTA. Teknik voltammetri dipilih karena memiliki sensitivitas yang tinggi, limit deteksi yang rendah, dan memiliki daerah linier yang lebar. Hasil penelitian memperoleh bahwa Cr(III) dapat dianalisis dengan EPK termodifikasi EDTA menggunakan teknik voltammetri lucutan. Kondisi optimum pengukuran yang diperoleh adalah menggunakan elektroda dengan komposisi grafit: EDTA 25% berat (w/w), larutan elektrolit NaCl 0,1 M, waktu deposisi 5 detik, dan potensial deposisi 300 mV. Carbon Paste Electrode Modified by EDTA for Determination of Cr(III) Reduced from Cr(VI) by Using Stripping Voltammetry Method: A Preliminary Study. This study presented a method of measuring Cr(III) using carbon paste electrodes (CPE) modified by EDTA, which could be applied in determining Cr(VI) waste indirectly. EDTA is a polydentate ligand that can chelate several metals. For chromium metal, EDTA can only chelate Cr(III). Therefore, a reduction of Cr(VI) to Cr(III) was carried out in the measurement process and then analyzed using an EDTA-modified carbon paste electrode. The technique was chosen because it has a high sensitivity, low detection limit, and has a wide linear area. The results showed that Cr(III) could be analyzed using EDTA-modified CPE using stripping voltammetry. The optimum measurement conditions obtained were using an electrode with a composition of 25% weight (w/w) EDTA, 0.1 M NaCl as supporting electrolyte, 5 seconds for deposition time, and 300 mV for deposition potential.

The aim of this research is producing the electrochemical sensor, especially for working electrodes based on the nanocomposites of multi-walled carbon nanotube (MWCNT) and magnetite (Fe3O4) nanoparticles from iron sands. The sonochemical method by ultrasonic horn was successfully used for the synthesis of the nanocomposites. The characterizations of the sample were conducted via X-Ray Diffractometer (XRD), Fourier Transform Infra-Red (FTIR) Spectrometer, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), Brunauer-Emmett-Teller (BET) method for surface area, Vibrating Sample Magnetometer (VSM) and Cyclic Voltammetry (CV). The analysis of X-Ray Diffraction (XRD) pattern showed two phases of crystalline, namely MWCNT and Fe3O4, peak of MWCNT comes from (002) plan while peaks of Fe3O4 come from (2 2 0), (3 1 1), (4 0 0), (4 2 2), (5 1 1), and (4 4 0) plans. From XRD data, MWCNT has a hexagonal structure and Fe3O4 has inverse spinel cubic structure, respectively. The FTIR spectra revealed that the functionalization process of MWCNT successfully generated carboxyl and carbonyl groups to bind Fe3O4 on MWCNT surfaces. Moreover, the functional groups of Fe-O bonding that showed the existence of Fe3O4 in the nanocomposites were also detected in those spectra. Meanwhile, the SEM and TEM images showed that the nanoparticles of Fe3O4 attached on the MWCNT surface and formed agglomeration between particles due to magnetic forces. Through Brunauer-Emmett-Teller (BET) method, it is identified that the nanocomposite has a large surface area 318 m2/g that makes this material very suitable for electrochemical sensor applications. Moreover, the characterization of magnetic properties via Vibrating Sample Magnetometer (VSM) showed that the nanocomposites have superparamagnetic behavior at room temperature and the presence of the MWCNT reduced the magnetic properties of Fe3O4. Lastly, the electrochemical characterization with Cyclic Voltammetry (CV) proved that Fe3O4/MWCNT nanocomposites with iron sands as the starting materials have high sensitivity and serve as excellent electron transfer materials. Based on the results of the research, the Fe3O4/MWCNT nanocomposites from iron sands are much recommended for electrochemical sensor.