ABSTRACT
Platinum (Pt) and platinum-nickel (Pt-Ni) electrocatalysts were prepared on activated graphite electrodes by an electrochemical deposition process. The electrocatalysts were analyzed by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). The electrocatalytic activity of the prepared electrocatalysts, their stability, and the effect of temperature toward ethanol and 2-propanol oxidation were evaluated by cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that the Pt-Ni/C exhibited higher catalytic activity, better stability and better tolerance to poisoning by ethanol and 2-propanol oxidation intermediate species compared to Pt/C, which was interpreted as synergistic and electronic effects between Pt and Ni. A study of the temperature dependence of ethanol and 2-propanol oxidation in the temperature range of 298-318 K, shows that the apparent activation energy for ethanol and 2-propanol oxidation on Pt-Ni/C was lower than on Pt/C. The results also revealed that the electro-oxidation of ethanol and 2-propanol on Pt/C were improved by raising the temperature and Ni modification.
ABSTRACT
Nanofiltration is generally used to separate monovalent ions from divalent ions, but it is also possible to separate ions of the same valency by careful application of the transfer mechanisms involved. Analysis of the retention of halide salts reveals that small ions like fluoride are the best retained, and that this is even more marked under reduced pressure when selectivity is greatest. The selectivity desalination of fluorinated brackish water is hence feasible and drinking water can be produced directly at much lower cost than using reverse osmosis by optimizing the pressure for the type of water treated.
Subject(s)
Fluorides/isolation & purification , Ultrafiltration/methods , Water Purification/methods , Water/chemistry , Diffusion , Ions/chemistry , Ions/isolation & purification , Minerals/isolation & purification , Nanotechnology/methods , Pressure , Sodium Chloride/isolation & purification , Solubility , Solutions/chemistryABSTRACT
Fluoride intoxication is a serious public health problem in Senegal. The concentration of fluoride ions in underground water in Senegal is higher than the acceptable standard (0.7 mg/l at 25 degrees C) varying between 5 and 15 mg/l according to the season. The hydrological pattern of fluoride ions in Senegalese water is presented. The high levels of fluoride ions are due to the presence of phosphate ores. The health problems associated with the ingestion of toxic doses (about 4 mg/l) are discussed. Epidemiological investigation shows that the intoxication in Senegal is serious. In addition to fluoride in drinking water, high levels are also found in food, particularly tea and vegetables. Nanofiltration is a low cost membrane-based process which can be used to eliminate fluoride from drinking waters. Also known as low pressure reverse osmosis, this process is selective for small molecules and ions. It can thus sterilize and partially demineralize water. Furthermore, it can require only small amounts of energy, such that it can be run from photoelectric cells.
