WO1997028090A1

WO1997028090A1 - Filter for drinking water filtration

Info

Publication number: WO1997028090A1
Application number: PCT/CZ1996/000004
Authority: WO
Inventors: Elizaveta K. Riabova; Ludmila B. Surmel; Nikolaj P. Stupin
Original assignee: Aqua Rosa, Spol. S.R.O.
Priority date: 1996-01-31
Filing date: 1996-01-31
Publication date: 1997-08-07
Also published as: EP0817758A1; AU4429996A

Abstract

Filter for purification of drinking water is designed for purification of both natural and tap water from chemical contaminants employing sorption methods based on using a mixture of strongly alkaline carboxyl catex in the form of H+ whose substantial function is based on the fact that strongly alkaline anex has a gel structure and it is washed with water down to value of chemical oxygen indicator max. 2 mg O2/dm3, catex with weak acidity has a macroporous structure with pores distribution according to the diameter size 1 - 9.104 nm 45 - 50 %, 1 - 5.102 nm 30 - 35 %, others less than 1.102 nm with volume ratio of anex to catex in the mixture 2:1.

Description

FILTER FOR DRINKING WATER FILTRATION

Technical Field

The invention relates to natural water and tap water purification. Sorption methods are used and the procedure could be used for drinking water preparation, including apparatuses used in households.

Background of the Invention

It is known that all natural water resources, esp. in densely populated areas, are polluted by chemical compounds both of natural and anthropogenic origin. Chemical compounds in water are often health threatening and this applies namely for heavy metals and organic compounds, like diesel fuel, herbicides and pesticides. Even tap water respecting valid normatives normative, often does not satisfy consumers due to its organoleptic features. Various methods are used for water purification according to intensity of its contamination. Water is filtered through active carbon, ultrafiltration membranes and specific sorbents. Each type of water purification equipment usually removes just one of water contaminants. For example, a water purification adaptor featuring active carbon allows for removing of a group of organic compounds from tap water, but it does not remove ions increasing water hardness, heavy metal contents, anions. There is known a filtration material improving drinking water quality in household conditions that consists of a layer of natural sorbent and a layer of resin mixture serving as anion and cation exchangers. However, water purification using the procedure is not sufficient. There is also known a water purification procedure being based on pouring water through an adapter filled with active carbon layer and an ion exchanging filter which comprises a styrene copolymer and divinylbenzol and a submicrone filter as well. Bacteria are removed from water purified in this way. A drawback of the above mentioned procedure is a complicated design of the filter adapter which is of a multilayer design and also a fact that no metal ions are removed from water. Another known water purification procedure allowing for a removal of toxic components from drinking water comprise water filtering by means of a material containing zirkon phosphate, filamentous material, for example viscose, impregnated with ferrocyanide, active carbon. Efficiency of removing lead reaches 97 - 98 %, and for phenol the value is 95 - 96 %. A drawback of the discussed procedure is a short lifetime of the material used and its destruction is followed by an increase of water content of heavy metals like zirkon and cyanide ions and with rapid decreasing of the filter material absorption ability. From the technical point of view, the most natural solution of the problem is a water purification procedure that includes water processing using a mixture of identical volumes of carboxyle catex with weak acidity based on metacrylate acid and strongly alkaline anex based on polystyrene. Sorbent is used under static conditions. In that way, cyanide, rhodanide ions, copper, zinc and iron are removed for water. The method manifests insufficient removal of heavy metals and is not capable to remove organic additives which means that obtained water cannot be used as drinking water. Sorbent has a low effectiveness during a dynamic regime as it is used in a form of irregularly shaped granules which are eroded by water stream, resins are destroyed, sorption efficiency is decreased.

Disclosure and Obήect of the Invention The foregoing problems and drawbacks are solved by a drinking water filter comprising a mixture of strongly alkaline anex on a polystyrene base in the form of 0H⁼ and carboxyl catex of weak acidity in the form of H⁺ constructed in accordance with the present invention comprising a strongly alkaline anex having a gel structure and a value of chemical oxygen indicator being max. 2,O mg O_^ /dm³ and a catex with weak acidity having a macroporous structure with pore distribution according to diameter size, i.e. 45 - 50 % of pores having size in a range of (1 - 9) .10⁴ nm, 30 - 38 % of pore size being in a range of (1 - 5) .10² nm and the rest of pores being smaller then 1.10² nm. Volume ratio of anex to catex in the mixture is 2 : 1.

Drinking water purification filter according the said design allows for increased level and complexity of water purification, increased process effectiveness during its application under dynamic conditions and also for higher filter adapter lifetime and durability.

Application of carboxyl catex of weak acidity in the filtration adapter in the form of spherical granules, that have a macroporous structure with certain pore distribution according to the size of their diameter, leads to doubling of the total exchange capacity due to using active groups on internal pore surface. It allows to increase intensity of metal ions adherence from water and also it makes possible removing of organic compounds of neutral type employing physical absorption which occurs due to non-ionogenic particles on the pore surface. Chemical sorption of organic compounds of acidic and alkaline types is provided for by resin carboxyl groups and neutral organic compounds are not removed both by catex and anex in usual industrial form. Application of strongly alkaline anex with gel structure ensures a close contact with spherical anex particles. In the same time, densely situated active groups with an opposite charge, make possible effective removal of hardly removable water contamination with strongly hydrated colloid iron, accompanied with destruction of multilayer hydroxide superficial layer of its particles. Volume ratio of anex to catex, swollen due to water processing 2 : 1 is chosen with respect to total exchange volume and specific resin swelling, and it ensures a neutral reaction of purified water. Resin is washed by gradual processing of an industrial resin with 10 % solution of HCl and NaOH with washed water between individual step and final washing. The efficiency of the filter is increased by water sorbent burden. The ratio of water to sorbent in the known process is (10 - 20) :1 and in the proposed process the ratio is 140 : 1. It means that for reaching the same step of purification much less amount of sorbent is needed. Usage of washed anex excludes its hydrolyse during washing with water which means occurrence of organic radicals in drinking water and also it increases the effect of anion removal from water.

Description of Examples of the Invention Application

Example 1.

As a basic water sample there was used a model water mixture with composition analogous to natural water, in which contaminant levels were increased 10 - 100 times, compared to tap water.

As a filter material there was used a mixture of swollen, strongly alkaline anex based on polystyrene gel structure in the form of OH- , the mixture being treated by washing to remove water soluble organic synthesis remains, to reach the washing water chemical oxygen indicator value of 1.8 mg 0₂ /dm³ , in amount of 200 dm³ , with 100 dm³ of swollen carboxyl catex of weak acidity with macroporous structure and with pore distribution according to the diameter size, namely 49% of pores having size in the range (1-9) .10" nm, 32% of pores with sizes in the range (l-5) .10²nm, the rest, ie.19% of pores smaller than 1.10²nm. The catex ingredient was in a form of regular spherical granules and it was mechanically solid.

The Sorbent mixture prepared as described above was inserted into an apparatus for water purification consisting of a cylindrical vessel into which pressurized water was directed from the vessel bottom with water flow of 0.2 dm³ per one minute. In total, 140 volumes of water columns were processed. The last dose was analysed and obtained results were compared to original water figures. Composition of original and purified water are summarized in the table presented bellow.

Example 2. Water from an underground source from a region near

Moscow was used as basic water sample. Water purification means and procedure are similar to those aapplied in the

Example 1. Composition of the basic and purified water are summarized in the table bellow. Discoloration of water obtained by the treatment was decreased from 30° down to 10° , a turbidity value was lowered from 3 to 1.5 mg/dm³.

Resin consumption for a filter volume of 0.3 dm³ used for additional purification of the above described Moscow tap water, having flow velocity of 0.2 dm³ /mi . amounts to 5000 dm³.

The described filter for drinking water purification enables to purify water to lower contaminant values then allowed by normatives for drinking water either natural or significantly contaminated water with the efficiency of 90 - 99 %.

The filtering mixture could be used repeatedly as it will last up to 100 sorption-regenerative cycles. One mixture filling in the filtration unit designed for using in households serves for obtaining and supplying drinking water for at least 1 year. Table

Water composition before and after purification using ion mixture and after passing through of 140 volumes of water columns and comparison of collected data with the PDK normative.

Indicator Sample solution Underground water PDK mg/dm³ region under Moscow

original purified original purified

pH 7,2 6,9 7,3 6,71 6,5-9,0 Total hardness (mg-ekv./l) 5,0 3,0 3,5 2,5

ChPK mg 0₂ /l 10,0 2,0 5,0 1,9 2, 0

Nitrates 20, 0 2,5 0,5 0,1 10

Fluorine 5,0 1,0 0,5 0,2 1,2

Sulphates 200 100 60 30 -

Cyanides 5, 0 0,05 0,02 0,01 0,1

Crude oil substances . 1,0 0,09 0,03 0, 01 -

Phenol 1,0 0, 01 0, 01 0, 00 -

Pesticides 1,0 nezjis . 0,01 0, 00 -

Iron 5, 0 0,2 0,5 0,2 0,3

Zinc 5,0 0,1 1,0 0, 05 -

Aluminium 5,0 0,03 0,5 0,01 0,05

Copper 5,0 0,5 0, 5 0, 05 0,05

Leado 1,0 0, 03 0,05 0, 01 0, 03

Cadmium 1,0 0,01 0,03 0,01 0,05

Quantity index 3 0 3 1 3 The invented filter enables additional tap water purification and improvement of its organoleptic quality. The amount of water contaminants is determined according their accumulation on resin during 30 - 40 days. The filter composed from a resin mixture of the described structure, enables production of disinfected water due to bactericide effect of the mixture, especially, after cumulating heavy metal ions killing bacteria. Due to this fact, even after exhausting of resin effect to cumulate heavy metals and salts causing water hardness, its bactericide effects persist and are preserved.

Industrial applications

Drinking water purification filter is designed for total tap water purification from various contaminants, like rust, heavy metals, organic compounds, chlorine, crude oil compounds. With the help of the filter, unpleasant odours are removed, as well as water turbidity and discoloration. Filtrated water is perfectly suited for drinking and food preparation. The filter can be used to obtain drinking water by various means of water treatment, including equipment used in households.

Claims

P A T E N T C L A I M

Drinking water puriification filter comprising a mixture of strongly alkaline anex on a polystyrene base in the form of OH^* and carboxyl catex of weak acidity in the form of H^* , c h a r a c t e r i z e d i n, t h a t the strongly alkaline anex has a gel structure showing a value of chemical oxygen indicator max. 2,0 mg O /dm³ and a catex with weak acidity has a macroporous structure with pore distribution according to diameter size, provided that 45 - 50 % of pores have size in a range of (1 - 9) .10⁴ nm, 30 - 38 % of pore size are in a range of {1 - 5) .10² nm and the size of rest of pores is smaller then 1.10² nm, while the volume ratio of anex to catex in the mixture is 2 : 1.