Study for Recovery of Uranium From Waste Effluent by Nitrogen Based Sorbent

8/3/2019 Study for Recovery of Uranium From Waste Effluent by Nitrogen Based Sorbent

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Study for Recovery of Uranium from Waste Effluent by

Nitrogen Based Sorbent

Document by:Bharadwaj

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ABSTRACT

A new type of granular sorbent with balance in diffusion assistance and cationic exchange

groups has been employed for treatment of effluent generated in uranium processing plant targeting

valuable recovery from the waste stream. The sorbent has been synthesized by two steps method. Infirst step homogeneously mixed acrylamide is polymerized with cross-linking agent followed by insitu

gelling of the whole mass and precipitation. In next step crumbled, washed and dried gel has beenconverted to a macro-porous chelating agent by reacting with hydroxylamine hydrochloride. The plant

effluent contains uranium in lower range of ppm level along with other metal ions, e.g., magnesium,

copper etc., where magnesium is the most competitive element. The effect of different operatingconditions such as concentration of uranium in effluent, pH and time required for uptake of uranium,

effect of presence of other element in effluent in uptake etc. in batch experiment have been

investigated.

Key Words: Sorbent, acrylamide, Hydroxylamine, Recovery, Effluent, Uranium, Parameters

1. INTRODUCTION

Uranium is the lifeline material of any nuclear industry. Recovery of uranium from its lean

sources has great significance world over in view of continuous depletion of uranium resources.

Recovery of uranium from its processing plants effluents is worth and in fact a mandatory

requirement due to its radioactivity and high toxicity. Recent studies (1-6) have revealed that uranium

recovery using a solid sorbent has the requisite potential to be promising as future method for recovery

of uranium from lean solutions.

It is also reported (7-9) that N-functional group based sorbents are efficient considering its

significant selectivity and higher kinetics. Among these, one is radiation grafted amidoxime type

sorbents, prepared following cost intensive radiation grafting route, whereas hydroxamate resins

starting from acrylamide are simple to prepare, low cost, eco-friendly, stable and more efficient. In

BARC, a promising sorbent, hydroxamate resin has been developed for recovery uranium.
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In Uranium Metal Plant (UMP) of Bhabha Atomic Research Centre (BARC) waste effluents are

generated in processing of different uranium compounds. Treated raffinate among the wastes, is

disposed from the plant as per approved procedure, having uranium ranging from 10 to 30 mg/l. A

detailed and systematic study is planned for evaluation of performance of the hydroxamate resin with

respect to uranium recovery from the treated raffinate effluent generated from the plant.2. EXPERIMENTAL

2.1 Reagent

Acrylamide, N,N' methylenebisacrylamide, hydroxylamine hydrochloride and sodium hydroxide

were used for preparation of the resin. These were procured locally are analytical reagent grade. No

pretreatment was applied to the reagents and used as received without any purification.

2.2 Sorbent preparation and Characterization

The sorbent is Polyacrylhydroxamic acid chelating resin (PHOA). It is prepared by mixing

required quantity of hydroxylamine hydrochloride with polymerized cross linked polyacrylamide

(PAAm). The sorbent has been synthesized by two steps method. In first step, homogeneously mixed

acrylamide is polymerized with cross-linking agent followed by in situ gelling of the whole mass and

precipitation. In next step crumbled, washed and dried gel has been converted to a macro-porous

chelating agent by reacting with hydroxylamine hydrochloride. The resulting mixture formed the resin,

is conditioned, washed, dried and crashed properly before use.

After drying the sorbent a certain quantity of sorbent was analyzed for size distribution. Sorbent

material with after uranium loading was analyzed by IR spectra using KBr pellatization for

understanding chemical bonding of the resin with uranium ions and by TGA spectra in nitrogen

atmosphere at a heating rate 100 C / min for getting imidization effect with respect to temperature.

2.3 Sample preparation and experimental procedures

Batch experiments were conducted using raffinate effluent solution from uranium metal

production plant. Chemical composition of the effluent has been given in Table 1. In the trial, a known

quantity of sorbent was equilibrated with a definite volume of the uranium solution. The effluent after

specified period of contact with the sorbent, separated from the sorbent and analyzed for uranium

content in the solution. The uptake of uranium ion by the sorbent was calculated by carrying out mass

balance of the uranium and which can be expressed as:

Q = [(C1-C2) V]/m

Where,


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Q= Amount of uranium ion sorbed on the dry sorbent (mg/g)

C1 & C2 = Concentration of uranium ion in the initial solution and in the final solution after

sorption at equilibrium respectively (mg/l)

V = Volume of the effluent solution taken for treatment (l)

m = Mass of the dry sorbent used (g)Forconcentration variation study 50 ml effluent solutions of concentration 1.5, 7.5, 15, 22.5

& 30 mg-U/l were taken in 100 ml flasks and similarly with pure synthetic uranium containing solution

treated with 0.5 gm sorbent for one hr. The treated solution was stirred thoroughly and filtered and

filtrate was collected for analysis. Other diluted solutions were prepared from the 30 ml/l solution

diluting with water.

For study ofuptake with time variation, experiments were carried out by contacting 0.5 gm

sorbent with 50 ml of 30 mg-U/l effluent solutions in a 100 ml conical flask. Contact time was varied

from 10 minutes to 240 minutes and after filtration samples were collected for uranium analysis.

Elution pH variation study:- Desorption was tested with varying HCl concentration from

0.1(N), 0.5 (N), 1.0(N), 3.0(N). The 50 ml effluent was contacted with 0.5 mg sorbent in 100 ml

conical flask for one hr in four different set-ups. After filtration the respective concentration of eluant

(15 ml each separately) was contacted with the loaded sorbent for desoption. The elute was analyzed

for uranium.

The uranium and metal ions were analyzed using Atomic Absorption Spectrophotometer.

3. RESULT & DISCUSSION

3.1 Characterization

Mesh size analysis shows that 72% of the sorbent beads are under 16-18 ASTM mesh size.

Uranium loaded sorbent characteristic shows that uranium is bonded as a result of strong interaction of

N-O group of resin with UO2+ ion(8). Thermogravimetic study indicates the stability of the resin w.r.t.

temperature change at 120c total moisture was removed followed by a decrease in temperature at

235C which is attributed to imidization reaction(8).

3.2 Concentration variation study

Effect of initial concentration of uranium in effluent and in pure synthetic solution has been

studied on uranium uptake of the sorbents is shown in Figure 1. The uptake value increases

progressively with an increase in initial concentration and an equilibrium value is achieved at uranium

concentration after 22 ppm which indicates completion of active binding sites on the sorbent. For pure


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synthetic solution it has been found that huge amount of uranium sequestration has been taken place

compared to the plant effluent solution. For example, for plant effluent uranium concentration is

125.25 ug/gm of resin, whereas the same for pure solution is 260.37 ug/gm of resin as a result of 30

ppm uranium containing solution. From Table 1 it is very clear that magnesium ion is one of the sole

competitors present in solution (percentage level) with uranium (in ppm level). However, the uptakecurve for plant treated effluent approaches to saturation, which is attributed to the limited number of

functional moieties present compared to uranyl and magnesium ions for engrossing the functional

moieties. It also reflects a competitive tendency of magnesium during chelation.

3.3 Effect of time on uptake

Figure 2 shows the effect of time on the uranium uptake when contacted with 30 mg/l solution

for a period of total 4 hrs with 10. 20, 30, 40, 50, 60, 240 minutes interval. All the experiments have

been carried out in separate batches. The graph clearly implies a sharp increase in sorption of UO22+

ions with reasonably faster kinetics and sorption completed within one hr. This period might be

considered as optimum time for contacting sorbent with effluent, after that the sorption rate slowed

down. Slower rate of the uptake is possibly because of unavailability of easily accessible functional

moieties and further swelling of the sorbent probably introducing the inner unoccupied chelating

groups.

3.4 Effect of pH on uptake

Response of sorption with the change of pH in initial solution is one of the crucial steps in

determining the efficiency of the sorbent as well as elution performance of the sorbent thereafter. Table

1 indicates the concentration level of uranium ions with interfering ions like Mg. Fig. 1 also indicates

the uptake of uranium significantly decreased due to the presence of other competing ions. Therefore it

is obvious, in elute uranium concentration may be affected due to the concentration of eluant. In Fig. 3

we have found with increasing concentration of acid during elution, uranium enrichment is taking

place. A strong tendency towards chelation is probably the reason which requires strong acid for

desorption. This phenomenon also indicates a significant selectivity and immobilization stability

towards uranium which is present in ppm level compared to magnesium that is in percent level.

4. CONCLUSION

A novel resin, namely Polyacrylhydroxamic acid chelating resin has been used to study the

uptake of uranium from effluent of uranium metal production plant. Sorptive features with the resin in


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contact with plant effluent studied for three main parameters. Initial concentration variation study for

uptake of uranium w.r.t synthetic and effluent solutions indicates a significant selectivity towards

uranium is lowered due to the presence of competing ions. In this regard a change in eluant

concentration enhances the pre-concentration value of uranium in elute. Further an improvement in

resin design and up gradation of process parameters with dose rate, feed solution pH, sorbent size,effect of degradation and losses in functional moieties are under investigation.

REFERENCES

1. Astheimer, L.; Schenk, H.J.; Witte E.G.; Schwochau, K.; Development of Sorbers for the

Recovery of Uranium from Seawater. Part 2. The Accumulation of Uranium from Seawater by Resins

Containing Amidoxime and Imidoxime Functional Groups; Sci. Technol. 1983, 18, 307

2. Kobuke, Y.; Tabushi, I.; Aoki, T.; Kamaishi, T.; Hagiwara, I.; Composite Fiber Adsorbent for

Rapid Uptake of Uranyl from Seawater; Ind. Eng. Chem. Res.; 1988, 27, 1461

3. Kabay, N.; Egawa, H.; Chelating Polymers for Recovery of Uranium from Seawater; Sep.

Sci. Technol. 1994, 29, 135

4. Chanda, M.; Rempel, G.L.; A Superfast Sorbent based on Textile-Grade Poly(acrylonitrile)

Fiber/Fabric. Rapid Removal of Uranium from Mildly Acidic Aqueous Solutions of Low

Concentration; Ind. Eng. Chem. Res. 42(22), pp. 5647-5655, 2003

5. Kavash, Pmar, A.; Seko, N.; Tamada, M.; Giiven, O.; Adsorption Efficiency of a Adsorbrent

Towards Uranium and Vanadium Ions at low Concentrations; Separation Science and Technology;

Vol. 39, No. 7, pp. 1631-1693, 2004

6. Ladeira, A.C.Q.; Morais, C.A.; Uranium Recovery from Industrial Effluent by Ion Exchange

Column Experiments; Miner. Eng., 18, pp. 1337 1340, 2005

7. Vernon, F.; Shah, T.; The Extraction of Uranium from Seawater by Poly (amidoxime)/Poly

(hydroxamic acid) Resins and Fibre; React. Polym.; 1983, 1, 301

8. Sangita Pal; Ramachandhran, V.; Prabhakar, S.; Tewari, P.K.; Sudersanan, M.;

Polyhydroxamic Acid Sorbents for Uranium Recovery; Journal of Macromolecular Sci., Part A: Pureand Applied Chemistry; 2006, 43, 735-747

9. Preetha, C.R.; Gladis, J.M.; Rao, T.P.; Venkateswaran, G.; Removal of Toxic Uranium from

Synthetic Nuclear Power Reactor Effluents using Uranyl Ion Imprinted Polymer Particles;

Environment Science Technology, 40(9), pp. 3070-3074, 2006


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Table 1: Composition of Raffinate Effluent of Uranium Metal Plant

Element Concentration

(mg/l)

Element Concentration

(mg/l)Al

B

Cd

Ce

Co

Cr

< 1

< 0.12


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Figure 2: Kinetics study of the sorbent with UED effluent

Figure 3: Effect of eluant concentration on the pre-concentration of uranium

Documents

Study for Recovery of Uranium From Waste Effluent by Nitrogen Based Sorbent