Liquid purification or separation – Processes – Ion exchange or selective sorption
Patent
1996-08-19
1998-12-08
Cintins, Ivars
Liquid purification or separation
Processes
Ion exchange or selective sorption
210917, B01D 1500, C02F 128
Patent
active
058464301
DESCRIPTION:
BRIEF SUMMARY
This application claims benefit of international application PCT/EP94 /04177, filed Dec. 15, 1994.
FIELD OF THE INVENTION
The present invention relates to effluent treatment. The present invention more specifically relates to a new adsorbent and its use in a process for removing residual dyes from effluents.
BACKGROUND OF THE INVENTION
The colour-using industries such as textiles industry, paper industry and leather industry produce effluent containing residual dyes which need to be removed.
It is already known from European Patent Application 91911139.3 that hydrotalcite like materials can be used to adsorb colours to low residual levels.
Any effluent treatment is characterized by the treatment of large volumes of effluent. In order to be cost effective when treating large volumes of effluents, there is a need for a process wherein addition levels of adsorbents are minimized.
Therefore there is a need for a process which enables a quick removal of residual dyes from effluents, in order to meet consent limits and in some instances to permit partial or total water reuse, while minimizing the use of adsorbents.
It has now been found that by adjusting the pH it is possible to dramatically increase the capacity of the adsorbent to adsorb dyes.
It has now been also found that by adding a magnesium salt to hydrotalcite-like materials, a synergistic effect is obtained which enables hydrotalcite like materials to be used much more effectively than before.
DEFINITIONS AND TESTS
i) Hydrotalcite like material
By hydrotalcite-like materials it is understood products which can be described by the formula below: combination of anions of similar or differing y- and k+2m+3n+4p-2-zy=0 and x can range from 1 to 100.
Examples of the cations M in the above formula are Li, Mg.sup.2+, Zn.sup.2+, Fe.sup.2+, Cu.sup.2+, Sn.sup.2+, Ca.sup.2+ and Sr.sup.2+. Suitable N cations include Al.sup.3+, Fe.sup.3+, Ti.sup.4+ and Sn.sup.4+.
Preferred divalent cations are Zn.sup.2+, Cu.sup.2+ or Mg.sup.2+ or a combination of these ions, or a combination with other divalent cations.
The anion A may be an inorganic or organic anion. Preferred inorganic anions A are Cl.sup.-, NO.sub.3.sup.-, SO.sub.4.sup.2-, CO.sub.3.sup.2- and OH.sup.-. Examples of organic anions are carboxylate ions such as citrate and stearate.
Examples of hydrotalcite-like materials of this invention are:
Preparation of hydrotalcite-like compounds is known and has been described in a number of publications including Solid State Ionics 22 (1986) pages 135-141 where there is published a paper by Walter T Reichle entitled "Synthesis of Anionic Clay Minerals (Mixed Metal Hydroxides, Hydrotalcite)" and Chemtech (January 1986) pages 58-63 where there is published a paper by Walter T Reichle entitled "Anionic Clay Minerals".
ii) Capacity
To measure the capacity of adsorbent to adsorb dyes the light absorbance (A0), before treatment, and the light absorbance (A1), after treatment are measured and the capacity is defined by
GENERAL DESCRIPTION OF THE INVENTION
It is a first object of the present invention to provide a process for removing residual dyes from effluents wherein the pH of the effluent to be treated is first lowered to between pH 4 and pH 5.5, an effective amount of hydrotalcite-like material being then added the effluent to be treated, the pH being then raised to above 7.
By first decreasing the pH and then creating a caustic chock, the capacity of the adsorbent to adsorb dyes has been found to be improved.
Preferably the hydrotalcite like material is a product which can be described by the formula below:
It has also been found that the addition of a zinc salt or a magnesium salt to the hydrotalcite like material after decreasing the pH and before raising it again gives rise to a further increase of the dye adsorption.
It is second object of the present invention to provide a new adsorbent containing: comprising magnesium salts, zinc salts and mixtures thereof.
Preferably, the (Hydrotalcite/Magnesium salt) weight ratio (on dry basis) is with in the range 20:1 t
REFERENCES:
patent: 4019982 (1977-04-01), Ikari et al.
patent: 4458030 (1984-07-01), Manabe et al.
patent: 4752397 (1988-06-01), Sood
patent: 5360547 (1994-11-01), Cockett et al.
Cockett Keith Robert
Webb Maurice
Whalley Roderick Terence
Cintins Ivars
Crosfield Limited
LandOfFree
Effluent treatment with hydrotalcite does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Effluent treatment with hydrotalcite, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Effluent treatment with hydrotalcite will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-173787