FR2543128A1 - PROCESS FOR REMOVING ORGANOPLOMB IONS, EFFLUENTS CONTAINING ORGANOPLOMB - Google Patents

Abstract

THE PROCESS FOR THE ELIMINATION OF ORGANOPLOMB IONS, FROM DILUTED AQUEOUS SOLUTIONS CONTAINING THESE IONS IN QUANTITIES (CALCULATED AS LEAD) UP TO 100PPM, WHERE THE SOLUTION IS PASSED THROUGH A BED OF CHEMICALLY CLEANED ZINC PARTICLES PROCEDURE FOLLOWING WHICH THE SOLUTION CROSSES SENSITIVELY CONSTANTLY FROM BOTTOM TO TOP THE BED OF ZINC PARTICLES, WHILE THESE PARTICLES ARE KEPT IN A STATE OF PERMANENT AGITATION. THERE IS NO NEED TO FILTER THE EFFLUENTS FIRST, AND AS SOON AS THE SOLIDS CARRIED OUT BY THE EFFLUENT THAT THOSE WHICH FORM BY REACTION OF ORGANOPLOMBS ON THE ZINC ARE TRAINED BY THE UPFLOW, TO BE SEPARATED LATER BY FILTRATION OR DECANTATION.

Description

The invention relates to the removal of organo

  -plumb of aqueous media, including but not limited to

  aqueous effluents from the manufacture of alkyl-

  -plombs. The discharge of waste liquors containing organoplomb compounds, as they occur, for example, in the manufacture of alkyl plumbs, presents a number of difficulties, both from the economic point of view and from the point of view of Environmental Pollution While Inorganic Lead Compounds Can Eliminate

  substantially, and at a reasonable cost, by pre-

  cipitation in solutions, this is not true of the

  For example, the aqueous effluents resulting from the manufacture of alkyl plumb are generally alkaline and contain significant amounts of sodium chloride, and in these media complex equilibria occur such as, for example R Pb + 2 C 1 = R 3 Pb Cl 2,

33 2

  which can exert a solubilizing effect on the organoplomb ions at the low concentrations considered Moreover, even when they precipitate the solution, the organoplomb precipitates are often of fine suspensions or emulsions which pass through the filters, do not decant easily , and

  do not coprecipitate with inorganic compounds.

  Various methods have been proposed to solve the problem.

  the effluent that contains organoplombs

  from the processes of manufacturing alkyl plumb, and

  This project, described in detail in US Pat. No. 3,697,567, comprises a two-step process where the effluent is first contacted with a more electropositive metal than the lead, but substantially nonreactive to water, followed by

  further treatment of the effluent, such as filtration, sedimentation

  In one process, the effluent is passed through a finely divided metal bed. In another process, the effluent is stirred into a bath containing the finely divided metal. divided Among the metals whose use is suggested in this process, it is said that zinc and iron

are preferred.

  In GB 1 417 078, the applicant describes a process for the removal of organoplomb ions from aqueous media containing relatively low concentrations of these ions, namely in amounts up to 100 ppm and more generally in the range 10 -100 ppm (calculated as lead) This process involves the passage of dilute solutions containing organoplomb from top to bottom through a column of chemically cleaned zinc particles, the periodic interruption of

  the circulation of the effluent or solution containing the organo-

  -plomb, and the washing in the opposite direction of the column with water at a pressure sufficient to cause the fluidization of packed zinc particles By the implementation of this method can be eliminated organoplomb ions very efficiently in a single pass, that is to say an elimination of more than 80%, often more than 90%, and these yields can be maintained over extremely long periods, for example 500 700 hours of continuous operation (except interruption

  periodic for washing the column in the opposite direction).

  The present invention proposes a modification of this

  This avoids several disadvantages encountered in the practical implementation of this process. These include the need for careful filtration of the alkyl lead effluents prior to passing through the column, to remove any entrained solid particles, which otherwise could cause

  clogging of the bed; the need for a uniform dimension

  thoroughly controlled zinc particles, so that the particles are fully fluidized during the washing step in the opposite direction, but without the risk that smaller particles are driven out of the bed by the washing liquid in the opposite direction; the need for a pierced plate to support the bed of zinc particles during circulation

  down the effluent through the bed, which one owes this

  during removal for periodic cleaning rather

  that it would otherwise be necessary to complete

  remove the bed of zinc particles; and finally the need for inter-

  periodic, albeit spaced out, effluents from -

  organoplomb through the column, for the washing step in reverse, any interruption of the flow of effluent through the column being a disadvantage for the treatment

  large volumes of diluted alkyl plumb effluent -

  by the continuous manufacture of alkylplombs.

  According to the present invention, these difficulties are avoided or mitigated by passing the diluted alkyl lead effluent, or any other dilute solution containing organoplomb ions, without prior filtration from bottom to top through a bed of zinc particles chemically cleaned, for example washed

  with acid, contained in a container, shaking the

  zinc effluent while the effluent is passed upward and discharged through the top of the vessel for further effluent discharge or treatment

depleted in organoplomb.

  Although the agitation of the zinc particles in the

  container can be obtained simply by the circulation of

  As a result of the effluent flow in the vessel, ie by fluidization of the bed, the preferred technique is to install an external-controlled mechanical stirrer, mounted on the bottom of the vessel, which serves to agitate the bed of water. Zinc particles Preferably, the agitator takes the form of a rotor blade, pivotally mounted on the base of the reactor vessel au;

  rotation of a vertical axis of rotation To prevent the

  the smallest zinc particles in the overflowing effluent, one or more deflectors may be arranged

  in the reactor above the bed of zinc particles.

  Practical tests have shown that, with continuous agitation, the activity of the bed of zinc particles can be maintained over extremely long periods, even in the absence of a washing step in the opposite direction, considered

  Previously, as essential In addition, the constant agitation

  the bed serves to prevent blockage of the bed by

  contents in the untreated effluent, or which are formed in situ in the bed by reaction between the zinc particles

  and the reactive compounds in the effluent These solids are

  washed from the bed by the rising liquid, and discharged from the upper part of the container with the treated effluent, which is then preferably filtered, or otherwise treated to eliminate

these solids before rejection.

  The treated liquid can be removed from the upper part

  in any suitable manner, but in order to contribute to a uniform and uniform flow in the container, the edge of this container is preferably spill-shaped, over which the treated effluent is

  vacant on all 3600 of the edge circumference.

  In preferred arrangement, the treated effluent discharged from the container is converted into a hydrocyclone or otherwise subjected to

  some form of complementary settling, the material

  sent back to the reaction zone This allows us to

  finer zinc particles, with a beneficial corollary increase of the available particle surface

for contact with the effluent.

  In yet another preferred embodiment, the treated effluent leaving the treatment vessel is subjected to a gas injection prior to discharge. This results from an experimental discovery that, upon contact with

  zinc, a significant proportion of trialkyl lead ions in

  reacts with tetraalkylploirb that drains with effluent

  The preferred gas injection treatment effectively eliminates

  tetraalkyl lead, leaving the effluent

  unleaded Any suitable inert gas may be used

  for injection treatment, but for economic reasons

  In the injection treatment, the air is preferred.

  gas, for example air, is preferably dispersed in the

  processed fluent contained in a stirred treatment vessel to provide substantially uniform dispersion

  air bubbles throughout the treated effluent.

  tion of the treated effluent can be carried out continuously with a residence time of the effluent in the aeration vessel of

-15 minutes.

  Also the initial treatment of the effluent and the aerator

  optional test are carried out properly at ambient temperature.

  Other treatment parameters are given below.

  after Zinc particle size General sieve range from 5 to 150 mesh (3.4 to 0.1 mm) Preferred sieve range from 5 to 50 mesh (3.4 to 0.3 mm) Effluent flow rate generally up to 0.75 volume per unit, although it is possible to work at moderately high temperatures, for example up to 50 ° C, preferably

will work towards 30 'C.

  Zinc particle bed volume per minute, preferably

  from 0.1 to 0.25 volumes per minute.

  The following method-the invention is illustrated by the following example.

EXAMPLE

  A cylindrical vertical container 230 mm in diameter

  and 1 m long is equipped with a closed plate agitator

  inclined, arranged very close to the bottom of the container Four

  edge deflectors, each about 250 mm high, are

  attached to the inner wall of the container at the lower end

  pool. A continuous circulation of aqueous effluents from a tetraalkyl lead plant is passed through the vessel from the base. An acid washed zinc feed is added to the 5 to 50 mesh sieve (3). 4

  0.3 mm), and started the agitator.

  The circulation was maintained for 53 days; during this time the flow varied between 2.3 and 9.1 liter / minute, with

  average over the whole of 3.8 1 / min We added new

  Zinc calf in time to maintain reaction efficiency The soluble organoplomb input concentration varied between 5 and 20 mg / l with an average over the whole

9.36 mg / l.

  The mean outlet concentration ranged from 1.0 mg / i for a flow rate of 2.3 l / min to 1.5 mg / l for a flow rate of 9.1 l / min, and was maintained at these values during the period of operation

Claims (1)

1 method for removing organoplomb ions from aqueous solutions containing such ions in amounts (calculated as lead) up to 100 ppm, where the solution is passed through a bed of zinc particles chemically cleaned, characterized in that it has been passed substantially substantially from bottom to bottom through the bed of zinc particles, while maintaining these particles in a state of permanent agitation. Process according to claim 1, characterized in that the solution flow rate through the bed is such as to maintain the zinc particles in said state of permanent stirring. Process according to Claim 2, characterized in that the particles are agitated by means of an external-controlled mechanical stirrer. Process according to any one of the claims   1 to 3, characterized in that, after passing through the bed of zinc particles, a gas is blown into the solution, before rejection.   Process according to Claim 4, characterized in that   that we blow into the treated solution of the air.