Removal of Hazardous Ions from Water by Photocatalytic Desalination Method
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Journal of Chemical, Biological and Physical Sciences An International Peer Review E-3 Journal of Sciences Available online at www.jcbsc.org Section A: Chemical Science ISSN 2249 –1929 Research Article Removal of hazardous ions from water by photocatalytic desalination method Shobha Rastogi1, Manisha Sindal2 and Ajay Sharma2 Department of Chemistry S. S. Jain Subodh P.G. College, Jaipur (Rajasthan) Department of Chemistry Government .P.G. College, Sirohi-307001 Received: 11 April 2011; Revised: 19 May 2011; Accepted: 29 May 2011 ABSTRACT Water is the most essential component of life. Though on a global scale, there is abundance of water but the main problem is the availability of water in the right place and in the right form. Rajasthan is declared as a desert state because it faces scanty rainfall. The population of Rajasthan is wholly depending on ground water resources and 50% of water resources are unpotable. In urban and rural areas of Rajasthan that have access to water, a sizable population has difficulty to use drinking water with TDS (Total Dissolved Salts) level more than 500 mg / Lt. which is allowed limit in accordance with BIS (Bureau of Indian Standards). Solar desalination process to obtain potable water is competitive with other means of obtaining potable water. Much work has been done in the field of collection of solar energy and its use in desalination process. In the present work, photocatalytic solar desalination process has been developed to obtain good quality of water. For this some metal catalyst were used to increase efficiency of the process. Copper Sulphide, Lead Sulphide, Antimony sulphide etc. are proved to be the best one. The work is restricted to ground water and samples have been collected from different areas of Sirohi district of Rajasthan. The water samples were analyzed for different. water parameters like pH, Salinity, TDS, Conductance, Total hardness etc. and data’s were compared with standards given by APHA 1998 (American Public Health Association). After solar desalination process again water samples were analyzed for the same parameters. The quantity J.Chem.Bio.Phy.Sci. 2011, 1, (Vo.1) 39 - 44 39 Removal of Hazardous Ions … Shobha Rastogi et al of water so produced was quite less and the rate was also very slow. Therefore, to enhance the rate of water production and to improve quality of desalinate water some photocatalysts have been used and found that TDS value of raw water is quite lower down by using these metal sulphides as photocatalysts. Keywords: Desalination, photocatalyst, alakanity, TDS. INTRODUCTION Rajasthan, the largest state of India faces a grim scenario in relation to water availability resources. Rajasthan has 2/3rd of its area as desert and it faces scanty rainfall. It would be seen from the present status of drinking water, that out of 237 blocks in Rajasthan, only 49 are safe in terms of ground water while 101 are critical and 86 are over exploited. It is a hard reality that state dependence on ground water is 91% for drinking water. On the other hand it is a fact that water pollution is one of the major problems facing humanity. Industrialization, urbanization, increase in human population are responsible for water pollution. If ground water is contaminated then, it’s necessary to remove contaminants from it before using water for domestic and drinking purpose. Shamrukh1 carried out research on impact of septic tank on ground water quality in Nile village of Egypt and found that it was the dangerous point source of ground water pollution. Studies of Chukawu Ogbonnya2 revealed that ground water is polluted from Acbattoir waste in minna. Due to this the required essential element was below expectation in drinking water. Research studies3 on status of ground water quality of Lalsot, urban area in Dausa district, Rajasthan revealed that this area has primary problem of salinity followed by nitrate contamination. Numerous of methods such as Ion exchange4, Distillation5, Reverse Osmosis6 , Activated Carbon Adsorption7, Electrodialytic desalination8, Solar desalination9 etc. have been developed to decontaminate water for make it potable. Rajasthan is blessed with ample amount of solar radiation and the part of this energy may be utilized to meet out drinking water need of remote area dwellers of Rajasthan. Solar Desalination10 unit is most appropriate because it is economical, easy to construct and maintain. For this purpose Bassam et al11 have fabricated a low cost high efficiency solar distill with porous evaporating surface. Bouchekima et al12, have performed the study of the capillary film solar distiller. G. E.Contos13 manufactured a solar still with two chambers. The lower chamber functions as salt water evaporator and upper chamber condenses the evaporate by means of naturally existing temperature differential. Cooper et al14 has shown that solar desalination technology is effective for bacterial decontamination and also found that Tio2 is photocatalytically active in the presence of sunlight. W.S. Kuo and P.H. Ho15 have applied 16 Tio2 film to solar photocatalysis of organic dyes. Baolinzhu et al have modified Paladium into Tio2 nanofibers (pd / Tio2 Nfs) by the degradation of methyl orange solution. S.C. Ameta et al 17 revealed that total volume desalinate water increases with increasing the exposure to sunlight and rate was further enhanced when work was done in the presence of photocatalysts like CuS, PbS etc. J.Chem.Bio.Phy.Sci. 2011, 1, (Vo.1) 39 - 44 40 Removal of Hazardous Ions … Shobha Rastogi et al MATERIALS AND METHODS Experimental: Study areas of Sirohi District. (1). (S1) - Barloot (2). (S2) - Doduwa (3). (S3) – Jhadoli (4). (S4) – Kalandri (6). (S5) - Manpur Ground water samples from 5 study areas were collected. Physicochemical studies have been carried out by checking the parameters such as salinity, TDS, conductivity, sulphate ions, pH etc. The result is reported in Table 1. All the Results were compared with the standard given by BIS (Bureau of Indian Standards). Photocatalysts like CuS, PbS, Bi2S3, Sb2S3 were used to get good quality of water. A layer of these semi conducting photocatalysts were coated on the trays and a part of solar desalination unit. It was observed that these photocatalysts materials have improved the efficiency of the process and also increased the rate of production to a remarkable extent of desaline water. This process has no side effect on environment. To enhance the rate of solar desalination, some semi conducting photocatalysts like PbS, CuS, Bi2S3, Sb2S3 were also used. In the present work, a thin coat of semi conductor sulphide was applied and then water was exposed to sunlight for hrs. After desalination, different parameters for water like pH, TDS, TH, conductance was again determined and results are reported in Table No.2. RESULT AND DISCUSSION 1. All the samples have pH value ranging between 7.5 to 7.9, a permissible range according to WHO, ISI, ICMR. 2. In the study area, Electrical conductivity ranged between 582 to 4990 micromhos /cm. The standard value given by United State Public Health Department is 350 micromhos /cm. Therefore, samples S3S4 and particularly S5 are not safe for drinking purpose. 3. Chloride concentration in S3, S4, S5 water samples have higher value but S1 and S2 water samples have chloride concentration within desired range. 4. Sulphate does not affect the taste of water. Sulphate in water samples of study area ranged between 4.7 to 618 mg/litre. 5. Nitrate is the highest oxidizable form of nitrogen and occurs in surface as well as ground water. The maximum permissible limit is 50 mg / Ltr (ICMR). In the study area, nitrate concentration is varied from 0.8 to 244 mg/Ltr. Sample S3 and S5 have high concentration of nitrate ion. J.Chem.Bio.Phy.Sci. 2011, 1, (Vo.1) 39 - 44 41 Removal of Hazardous Ions … Shobha Rastogi et al 6. Hardness of water caused by multivalent metallic cations varies considerably from place to place. In the present study T.H. as Calcium Carbonate varies between 192 to 1110 mg /ltr. The maximum permissible value for T.H. is 600 mg/ltr (ICMR). Thus S3 and S5 water points are very hard. 7. Quantity of calcium in natural water depends on the type of rocks. It is leached and contaminates the water. Calcium in water samples is ranged between 47 to 211 mg/Ltr which is the permissible range (ICMR) 8. The maximum allowed value of magnesium in water is 150 mg/ltr (WHO). All the samples have magnesium within permissible limits. 9. The guideline value of fluoride in drinking water is 1.5 mg/ltr. The excessive amount of fluoride causes disfigurement of teeth. In the present study fluoride concentration is ranged in between 1.78 to 3.15 mg / ltr indicating higher concentration of fluoride. 10. The standard range for Iron in ground water is 0.1 to 1 mg/ltr (WHO and ICMR). Smaples S1, S2 and S3 have the values within permissible limits but S4 and S5 have higher Iron concentration. 11. The maximum permissible limit for TDS is 1500 mg/Ltr (ICMR). Gastrointestinal irritation is caused due to higher concentration of TDS. The TDS value varied from 385 to 3340 mg/ltr. In the study area, samples S3,S4, and S5 have higher value of TDS. CONCLUSION From the above table it may be concluded that – 1. These metal sulphides proved to be very useful for reducing TDS value. 2. pH value of water could easily be controlled with a use of metal sulphide photocatalysts. 3. Total Alkanity is also reduced by the use of above metal sulphides as photocatalysts. 4. To reduce the Total Hardness of water, PbS is proved to be the best one among all the four metal sulphide photocatalysts.