Abstract
Granulated micelle–clay complexes including the organic cation octadecyltrimethylammonium (ODTMA) were shown to be efficient in removal of total bacteria count (TBC) from water. Microwave (MW) heating of granules to restore bacterial removal was investigated. Drying of granules by MW required 20-fold less energy than by conventional heating. When water content of granules approached 10%, or less, their heating period by MW had to be below 1 min, e.g., 30 s, and less, in order to avoid ignition and irreversible structural changes. Structural and thermal properties of MW heated samples were studied by FT-IR spectra and thermo gravimetric analyses (TGA). Inactivation of bacteria in water was more efficient by MW than by conventional oven, or by electric plate. For elimination of bacteria from water, MW heating was at least five-fold more efficient than by conventional heating. The results have established an adequate regeneration procedure by MW heating at durations depending on the remaining percentage of water associated with the granules. Tests of first and second regenerations by MW heating, and HCl washing of columns, were carried out. It was concluded that MW treatment may be chosen for optimal regeneration of the granulated micelle–clay complex as an efficient and low-cost procedure.
Highlights
A general goal of drinking water treatment is to reduce health hazards due to pathogenic microorganisms in water using minimal concentrations of disinfectants
A sample of 5 grams of ODTMA– or BDMHDA–clay granules was subjected to the MW irradiation for 90 s, 180 s, 270 s, 360 s, and 450 s
An evaluation of the maximal number of bacteria that could be retained by 1 g of the complex [5,8,9]
Summary
A general goal of drinking water treatment is to reduce health hazards due to pathogenic microorganisms in water using minimal concentrations of disinfectants. Chlorination at high doses of water, which includes organic molecules at concentrations of the order of mg/L, results in production of trihalomethanes (THMs) and haloacetic acids (HAAS), whereas reduced efficiency in eliminating some epidemic microorganisms occurred at low doses [1]. Disinfection by chloramines results in formation of nitrosamines [2]. Ozone is powerful in removal of microorganisms, but its application results in formation of nitrosamines [3] and cyanogen halides [4]. Filtration by means of a granulated micelle–clay complex has been proposed as one possible solution for reducing harmful disinfection byproducts (DBP). The micelle–clay complexes were synthesized by interacting micelles of an organic cation with a clay, which has a relatively large surface area.
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