|Title of Invention||
AN IMPROVED PROCESS FOR PREPARATION OF ALUM IMPREGNATED TEA LEAVES CARBON FOR DEFLUORIDATION OF DRINKING WATER
|Abstract||An improved process for preparation of alum impregnated tea leaves carbon useful for defluoridation of drinking water: The present invention relates with an improved process for preparation of alum impregnated tea leaves carbon useful for defluoridation of drinking water. The tea leaves carbon was impregnated with different strength of alum solution. 4% alum impregnated tea leaves carbon provided improved defluoridation in the field. The pore size of < 125µm was also very effective.|
|Full Text||The present invention relates to an improved process for the preparation of alum impregnated tea leaves carbon for defluoridation of drinking water.
The present invention has been designed with the aim to facilitate defluoridation of drinking water in fluorosis endemic areas at household level with improved efficiency.
References may be made to Kempf C.A., Galligan, W.E., Green wood, D.A. and Nelson, V.E., Proc. Iowa Acad^Sci. 43, (1936) 191-195; Boruff , C.S., Buswell, A.M. and Upton, W.W. Ind. Engrg. Chem., 29, (1937) 1154; and Scott, R.D., Kimberley, A.E., Van, A.L, Horn, LF.Ey. and Waring, F.H. J. Am. Water Works Assoc., 29 (1937) 9-25 wherein alum was used for defluoridation of water. When added to water, alum reacted with the alkalinity in water to produce insoluble AI(OH)3. The fluoride ions were removed from the water by adsorption on AI(OH)3 particles followed by charge neutralisation, enmeshment in a sweep floc and precipitation. The drawbacks of this process are that huge doses of alum are required to accomplish desired level of defluoridation.
References may be made to Gulp, R.L. and Stoltenberg, H.A. J. Am.
Water Works Assoc., 50 (1958) 423-31 wherein 225 mg/l of alum was used for
defluoridation of water in the pH range corresponding to the minimum
solubility of AI(OH)3 for reducing fluoride concentration to 1.5 mg/l from soft
highly mineralised water containing 3.6 mg/l of fluoride. To reduce fluoride
concentration to 1 mg/l 315 mg/l of alum dose was required. The results
varied among researchers because of variation in fluoride concentration in
water, duration of mixing and pH of the solution but there was consistency
about the fact that large doses of alum would be required for defluoridation.
The treatment with alum also produces sludge. Reference may be made
to Benefield L.D., Judkins, J.F. Jr. and Weand, B. L. Process Chemistry of Water and Waste water treatment. Prentice Hall Inc. Englewood Cliffs, New Jersey, USA (1982) wherein if the raw water is treated with an alum dose of 25 mg/l the volume of sludge produced for one million gallons per day flow will be 323.94 gallons.
The use of alum also reduces alkalinity. Reference may be made to Benefield L.D., Judkins, J.F. Jr. and Weaned, B. L. Process Chemistry of Water and Waste water treatment. Prentice Hall Inc. Englewood Cliffs, New Jersey, USA (1982) wherein each mg/l of alum consumes 0.5 mg/l of calcium carbonate and produces 0.44 mg/l of carbon dioxide. If the natural alkalinity is not sufficient to react with the alum and buffer the pH, it is essential to add soda ash or lime to sustain alkalinity to the water.
Reference may be made to Nawlakhe, W.G., Kulkarni, D.N., Pathak, B.N. and Bulusu, K.R. Ind. J. Environ. Hlth. 17 (1975) 26-65 wherein lime, bleaching powder and alum are used in a sequence followed by flocculation, sedimentation, filtration and sludge concentration for fluoride removal. The fluoride removal depends upon the alum dose, fluoride concentration and alkalinity of water. However, if total dissolved solids was >1500 mg/l and hardness was >600 mg/l desalination became necessary. If hardness ranged between 200-400 mg/l softening was necessary to supplement the technique. The selection of either aluminium chloride or aluminium sulphate depended on chloride and sulphate concentration respectively. The quantity of chemicals required is too high and the floes produced also do not settle rapidly particularly in waters that are low in turbidity or low mineralised waters that are coloured. The process also required regular water quality monitoring before the use of chemicals.
Reference may be made to Nair, S., Jallan, G. and Pandey, G.S. Fluoride, 23, (1990) 35-36 wherein alum waste and calcium hardness induced slow fluoride removal in early stages followed by fast removal resulting in total fluoride removal in three days.
For rapid settling coagulant aids viz. clays, activated carbon etc. can be added to improve floe properties and enhance coagulation.
Reference may be made to RabovsKy, J.G. and Miller, J.P. 29th Purdue Ind. Waste Conf. (1974) 669-676 wherein fluoride removal was carried out using a two stage process of lime precipitation followed by alum and polyelectrolyte coagulation. The initial fluoride concentration of 200 mg/l was reduced to 4-6 mg/l following lime precipitation. The concentration was further reduced by adding 25 mg/l alum and 2 mg/l polyelectrolyte. The optimum pH for coagulation was in the range of 6.0 to 7.0. The drawback of this process is the sensitivity of polyelectrolyte to contamination. They are easily fouled and choked by particulate matter.
Reference may be made to Arulanantham, A., Ramakrishna, T.V. and Balasubramanian, M. Ind. J. Environ. Protect. 12 (1992) 531-536 wherein carbon derived from coconut shell was impregnated with aluminium ions and when used in wet conditions removed three times more fluoride as compared to the same material used after drying. The coconut shell was prepared by treating one part of coconut shell pieces with 1.5 part by weight concentrated sulphuric acid and keeping it in an air oven maintained at a temperature of 140-160°C for a period of 24 hours. The carbonized material was washed with water to remove free acid and dried at 105 ± 5°C. The material was sieved to separate particles of 20-40 mesh. 50 gms of the prepared material was digested with 200 ml of 2% NaHCO3 solution for 30 minutes. The material was
washed and digested for 30 minutes with 2% alum solution. The precipitated AI(OH)3 was solubilizied using 1:1 HCI and the material left in the solution overnight. The pH range was 3.2-3.5. The material was washed dried at 105 ± 5°C for 6 hours and sieved in the range of 20-40 mesh size. The drawback of this process is the use of wet material. Use of dried and sieved material could increase the amount of adsorption possibly due to the loss of adsorbed moisture. Further, the duration of carbonization was high which could produce a sorbent with high meso porosity and low micro porosity . Reference may be made to Girgis B.S., Khalil, LB. and Tawfik, T.A.M. J. Chem. Tech. Biotechnol., 61 (1994) 87-92 wherein prolonged carbonization has been reported to lead a product with high meso porosity and low micro-porosity.
Reference may be made to Wenjie, He., Jun, Z. and Zhang, H. Faming Zhuauli Shenquing GongKai Shnomingshu. Pat. No. CN 1037465 (Cl B01D53/04. Chemical Abstract 113: 65028 (1989) wherein one part of saw dust (by weight) and 2.5% water glass (binder) calcined at 800°C for six hours. The material was immersed in 3% AI2(SO4)3 for four to eight hours and washed with clean water before being used for defluoridation. It is not possible in remote areas to generate a temperature of 800°C for preparation of material and to procure a binder.
Reference may be made to Rubel, F. and Woosley, R.D. EPA. Tech. Rep. EPA 570/7-78-001 (1978) U.S.A.; Wenbin, W., Yuzhi, D., Ran, Z., Xiaoxia, W. and Chen, J. Sin. Chuli Jishu. 17, (1991) 406-408. Chemical Abstract 116:221135; Chaturvedi, A.K., Yadava, K.P., Pathak, K.C. and Singh, V.N. Water Air and Soil Poll. 49, (1990)51-61; Mwaniki, D. and Nagelkerke, N. Med. Biol. Eng. 2, (1990) 303-308 wherein activated alumina, zeolite, bone and bone char had been used for defluoridation. However, activated alumina
and zeolite are not available universally, while bone and bone char are not acceptable on the basis of ethical considerations.
References may be made to Serranol V.G. and Ramos, M.A. J. Chem. Tech. Biotechnol., 68, (1997) 82 - 85 wherein activated carbon was heated at 250°C for 2 hours. The material cooled and soaked with sulphuric acid for 2 hours at 70°C and at 30°C for 6 hours. The supernatant decanted and sample dried in oven at 60°C for 2 hours. By drying at such low temperature sulphuric acid remained in the sample. The characterization revealed that it had little impact on its surface area. The main object of the present invention is to provide a process for the preparation of alum impregnated tea leaves carbon for defluoridation of drinking water which obviates the draw backs as detailed above. The process have several novel features:-
• It reduces carbonization time
* Carbonization occurs at low temperature.
Accordingly the present invention provides an improved process for preparation of alum impregnated tea leaves carbon useful for defluoridation of drinking water which comprises washing used tea leaves with hot and then with cold water, drying in an oven at range 80°-120°C, carbonizing the said dried tea leaves for 8 - 10 hours by conventional method with mineral acids as herein described, wherein ratio of tea leaves and acid is 1 : 1 gm /ml and temperature ranges between 130°C - 200°C, neutralizing the carbonized tea leaves as obtained by repeated wash with distilled water drying and sieving through a mesh of pore size In an embodiment of the present invention the mineral acid used for carbonization is selected from hydrochloric acid, nitric acid, phosphoric acid and sulphuric acid, preferably sulphuric acid.
In another embodiment of the present invention dried leaves were treated with concentrated mineral acid (LR & GR grade) in the ratio of 0.3 to 3.0 gms tea leaves per 0.5 to 3.0 ml of acid and carbonized over hot plate for 8-10 hours at a temperature of 130°C-200°C with a slow initial increase of temperature followed by heating for 2-3 hours at above mentioned temperature. In still another embodiment of the present invention 20-30 gms of tea leaves carbon material was stirred with 1 Qfi-300 ml of 0.5-4.0% alum solution at 20-40 rpm (rotation per minute) for 3-15 days at pH of 3.0-4.0. It was followed by decanting the supernatant and washing the material with distilled water, drying in an oven at a temperature of 80-120°C and sieving to a pore size of The used tea leaves were procured from tea stalls and other sources.
The material was washed repeatedly with hot and cold water to remove milk
content. The material was washed with distilled water and dried in an oven
at 80-120 °C to remove moisture content. The dried tea leaves were
treated with concentrated hydrochloric acid/ nitric acid/ phosphoric acid/
sulphuric acid (LR/GR grade) in the ratio of 0.3 to 3.0 gms of tea leaves per 0.5
to 3.0ml of acid and carbonized over hot plate for 8-10 hours at a temperature
of 130-200°C. The temperature was slowly increased followed by heating for
2-3 hours at above mentioned temperature. The material was cooled and
washed repeatedly with distilled water till pH of the rinse water is at or near
neutral to remove any excess acid. The material was dried in an oven at 80-
120°C, cooled and passed through a sieve of pore size of tea leaves carbon was brought in contact with 100 to 300 ml of 0.5-4%
potash alum (AR grade) solution at a pH of 3.0-4.0. and agitated in a shaker
for 3 to 15 days at 20 to 40 rpm. Thereafter, the supernatant was decanted,
the material was washed with distilled water and dried in an oven at 80-120°G, cooled and passed through a sieve of pore size The product developed has several new features over the processes
developed in the prior state of art. The drying of material before carbonization
speeded up carbonization. The carbonization of the soft material leads to
vigorous evolution of gases and tarry material in early stages. Heat
pretreatment also speeded up the penetration of the acid into the material
possibly due to the loss of the water molecules. The acid pretreatment
neutralized part of the negative charge and generated positively charged
sites for the adsorption of fluoride. The concentrated sulphuric acid was most
effective of all acids as it enhanced dehydration producing micro-porous char.
The ratio of tea leaves to sulphuric acid may be at 1gm/ ml acid. The reduction
in carbonization time and carbonization at low temperature as compared to the
prior state of art provided a micro porous product. The micro porosity of tea
leaves carbon prepared by this method is about 85%. The sorbents with high
micro porosity are better adsorbents. 95% of the surface area in the
commercial activated carbon is micro porous..
The process of alum impregnation was improved for field use. In laboratory studies the tea leaves carbon impregnated with 2% alum solution provided efficient defluoridation. However, during field trials it was realized that in areas where fluoride concentration is high impregnation with 2% alum solution is not providing efficient defluoridation. Hence the tea leaves carbon was impregnated with different strength of alum solution and tested for defluoridation. 4% alum impregnated tea leaves carbon provided improved defluoridation in the field. The pore size of while in case of very low pore size the particles floated on the surface instead of settling down making decantation difficult.
The process of using material after drying had an advantage over the prior state of art in using the material in the wet stage. Heat pretreatment at 80-120°C of the sorbent increased the amount of defluoridation possibly due to the loss of adsorbed moisture.
The process also reduced the quantity of alum consumption. In the process the floes settled faster because tea leaves carbon acted as a weighing and nucleating agent. In the process the sludge production is also low because of decrease in use of alum. The fluoride containing water is stirred with material in a bucket. The material is allowed to settle and the supernatant decanted to provide water containing fluoride within the permissible limit. The small quantity of sludge being produced could be concentrated in a lined evaporation pond with eventual fluoride recovery by an industry.
The following examples are given by way of illustrations and therefore should not be construed to limit the scope of present invention.
The material for defluoridation of drinking water was prepared procuring used tea leaves from different sources. The tea leaves were washed with warm and cold water to remove milk content and then washing the material with distilled water. The material was dried in an oven at 120°C. The dried tea leaves material was treated with concentrated sulphuric acid (LR grade) in the ratio of 1gm of tea leaves per ml of the acid. The mixture was carbonized over hot plate for 10 hours at a temperature of 130°C. The temperature was raised slowly followed by heating for 3 hours at above mentioned temperature. The
carobnized material was cooled, washed with distilled water till pH of the rinse water is at or near neutral to remove excess acid, dried in an oven at 120°C, cooled and passed through a sieve of pore size Example - 2
20 gms of prepared tea leaves carbon was treated with 200 ml of 0.5 - 4% potash alum solution at pH 3.2 at 20 rpm for 7 days. The supernatant was decanted, the material washed with distilled water. The material was dried in an oven at 120°C and sieved to a pore size of Example - 3
The tea leaves carbon (TLC) and 2% alum impregnated tea leaves carbon were tested in the laboratory with Industrial Toxicology Research Centre (ITRC), Lucknow tube well water spiked with fluoride to yield 10 mg/l fluoride concentration in water. The sorbent prepared was tested for defluoridation in the kinetic adsorption and equilibrium adsorption batch experiments. The defluoridation results are as shown in fig. 1 & 2. Table 1 shows the physicochemical characteristif of ITRC, lucknow tube well water.
Example - 4
Water sample collected from Marksnagar, Unnao (UP.., India) was subjected to defluoridation. The tea leaves carbon was impregnated with 0.5%, 2% and 4% alum. The Fig. 3 & 4 show % fluoride removal with tea leaves carbon impregnated with different % of alum solution. Table 1 whows the physico-chemical characteristics of water from Marksnagar, Unnao (U.P., India).
Example - 5
Another field trial was carried out on a sample collected from Deo Singh Khera village, Gosainganj, Lucknow (U.P., India), which had highest fluoride concentration. Fig. 5 & 6 show % fluoride removal with 4% alum impregnated tea leaves carbon. Table 1 shows physico-chemical characteristics of water from Deo Singh Khera village, Gosainganj, Lucknow ( UP., India).
The main advantages of the present invention are:-
1. Improved efficiency of defluoridation with alum impregnated tea leaves
2. A process of preparation of tea leaves carbon and alum impregnation is
simpler and easier.
3. Easy availability of the material.
Table 1. Physico-Chemical Characteristics of different sources of Drinking Waters
ND- Not Detected;
All values in mg/l except pH and Electrical Conductivity values
Electrical Conductivity values in µmhos/cm
1. An improved process for preparation of alum impregnated tea
leaves carbon useful for defluoridation of drinking water which
comprises washing used tea leaves with hot and then with cold
water, drying in an oven at range 80°-120°C, carbonizing the said
dried tea leaves for 8 - 10 hours by conventional method with
mineral acids as herein described, wherein ratio of tea leaves and
acid is 1 : 1gm/ml and temperature ranges between 130°C -
200°C, neutralizing the carbonized tea leaves as obtained above
by repeated wash with distilled water drying and sieving through
a mesh of pore size 4% potash alum solution for a period of 3 - 15 days at a pH ranging
3.0 - 4.0, drying and sieving through a mesh having pore size as
defined above, to get the desired alum impregnated tea leaves
2. A process as claimed in claim 1 wherein the tea leaves used is
preferably used tea leaves collected from tea stalls and other
3. A process as claimed in claims 1 - 2, wherein mineral acid used is
selected from hydrochloric acid, nitric acid, phosphoric acid and
4. An improved process for preparation of alum impregnated tea leaves carbon for defluoridation of drinking water substantially as herein described with reference to the examples accompanying this specification.
|Indian Patent Application Number||45/DEL/2001|
|PG Journal Number||38/2007|
|Date of Filing||19-Jan-2001|
|Name of Patentee||COUNCIL OF SCIENTIFIC AND INDUSTRIAL RESEARCH|
|Applicant Address||RAFI MARG, NEW DELHI - 110 001, INDIA.|
|PCT International Classification Number||C02F 1/58|
|PCT International Application Number||N/A|
|PCT International Filing date|