A sensitive spectrophotometric method for determination of carbon tetrachloride with the aid of ultrasonic decolorization of methyl orange

A simple equipment and colorimetric method for determination of chloroform in water

Chlorination is a common and successful method for disinfection of water all around the world, especially in developing countries. However, this process can produce trihalomethanes (THMs) byproducts which are carcinogen. The major THM occurring in this process is chloroform. The purpose of this study was to design a simple equipment for colorimetric determination of chloroform in various water samples. The method is based on the colorimetric reaction of chloroform with resorcinol in strong basic medium on a filter paper. Response surface methodology (RSM) was employed to optimize the determination condition. The reagents were immobilized on filter paper and the color change was followed to quantify chloroform without using any analytical instrument. Detection limit and linear range of the proposed method were 0.007 mg/L and 0.011-1.192 mg/L, respectively for analysis of samples with volume of 2.0 L. The method was successfully applied to determine chloroform in different water samples and compared with GC-MS as a standard method. Employing the designed device, purge, trap and analysis steps were performed in a single run which can reduce the uncertainties originated by excessive steps of the analysis.

Intensification of sonochemical decolorization of anthraquinonic dye Acid Blue 25 using carbon tetrachloride

In this work, the influence of CCl(4) on the sonochemical decolorization of anthraquinonic dye Acid Blue 25 (AB25) in aqueous medium was investigated using high frequency ultrasound (1700 kHz). This frequency, reputed ineffective, was tested in order to introduce the ultrasound waves with high frequency in the field of degradation or removal of dyes from wastewater, due to its limited use in this field, and to increase the application of high frequency ultrasound wave in the field of environmental protection. The effects of various parameters such as the concentration of CCl(4), frequency (22.5 and 1700 kHz), solution pH, temperature and tert-butyl alcohol adding on the decolorization rate of AB25 was studied. The obtained results clearly demonstrated the significant intensification of AB25 decolorization in the presence of CCl(4). The enhancement effect of CCl(4) increased by decreasing temperature and by increasing the CCl(4) concentration. The pH has a significant influence on the bleaching of dye both in the absence and presence of CCl(4). The three investigated dosimeter methods (KI oxidation, Fricke reaction and H(2)O(2) production) well corroborate the improvement of the sonochemical effects in the presence of CCl(4). The best sonochemical decolorization rate of AB25 in aqueous solution both in the absence and presence of CCl(4) is observed to occur at 1700 kHz compared to 22.5 kHz. The sonochemical oxidation of CCl(4) generates oxidizing species in the liquid phase that are highly beneficial for oxidation of hydrophilic and non-volatile pollutant, such as dyes, because they are less susceptible to free radical attack due to lower stability of the generated free radicals.

Spectrophotometric determination of carbon tetrachloride via ultrasonic oxidation of iodide accelerated by dissolved carbon tetrachloride

Ultrasonic oxidation of iodide was investigated in the presence of carbon tetrachloride (CCl4). The ultrasonic oxidation of potassium iodide led to formation of iodine and then I3(-) in the presence of excess iodide, and the generated I3(-) shows strong UV absorption with a molar absorptivity of 2.31x10(4) L mol(-1) cm(-1) at the maximum absorption wavelength of 351 nm. The ultrasonic oxidation of iodide was found to be significantly promoted by a small addition of CCl4, and it was further found that the generation rate was increased with the amount of CCl4 added. This can be used to analyze the level of CCl4 dissolved in aqueous solutions. Under optimum conditions, the concentration of generated iodine (or its absorption at 351 nm) was found to correlated linearly with the concentration of CCl4 in the range of 0.2-50 mg L(-1) (detection limit = 0.09 mg L(-1), R2 = 0.999). As an alternative indirect spectrophotometric method of CCl4 determination, the proposed method was successfully applied to determine the concentrations of CCl4 in several practical samples, showing merits of being sensitive and simple of operation.