ABSTRACT
Alkaline ionized water (AIW) is a therapeutic drinking water having pH greater than 7, a negative oxidation-reduction potential (ORP), and micro-clusters of water molecules for rapid hydration. Consumption of AIW is proven to have several health benefits for humans. It is used as an adjunct in prevention of hyper acidity, cancer and diabetes. There are very few AIW production devices available across the globe, most of them being cost-intensive and not affordable to the average person. Therefore, this work focuses on the design and development of a polymeric membrane-based, cost-effective electrolyzer in batch and continuous modes of operation. A batch mode AIW unit of 20 L capacity is constructed using a flat-sheet ion exchange membrane of 50 cm2 area that produces 20 L of 9.5 pH water in 15 h. The smaller table top AIW unit could process 200 mL of neutral pH water to pH 9.5 in just 15 min., by utilizing a membrane of molecular weight cut-off (MWCO) of 5 kDa and an area of just 40 cm2.The continuous electrolyzer of 2.35 L/h capacity was designed using a hollow fiber membrane module of effective membrane area 450 cm2 and MWCO of 30 kDa. Ultrafiltration membranes based on polyethersulfone (PES) and polysulfone (PSf) were synthesized and used for AIW generation. The performance of the electrolyzer was evaluated in terms of feed TDS, flux, electrode durability, operating time, membrane stability and power consumption for the production of alkaline reduced water. In the case of the continuous AIW unit, stainless-steel (SS) electrodes were found to be suitable, while in the case of the batch electrolyzer, titanium anode is used to avoid corrosion problems. A pH of 10 could be attained at flux of 3.33 L/h in continuous mode using hollow fiber module, while batch mode electrolyzer exhibited 2.22 L/h and 2 L/h with PES and PSf membranes, respectively. The developed electrolyzers were found to be effective in producing AIW of 9.5 pH by considering drinking water from nanofiltration (NF)/reverse osmosis (RO) as feed and utilizing power from 36 V DC adapters, wherein the average current was 0.4 A. The capital cost of 20 L batch AIW unit, hollow fiber based continuous unit and 200 mL table top unit worked out to be only Rs. 1025/-, Rs. 2500/- and Rs. 410/-, respectively, which are all several notches less than commercial AIW units.
