DESALINATION

ELSEVIER Desalination 106 (1996) 4 19-422

Total removal of heavy metal from mixed plating rinse wastewater

Nasiman Saparia*, Azni Idrisb, Noor Hisham Ab. HamidC

UFacul& of Science and Environmental Studies, C’niversiti Pertanian Malaysia, 43400 Serdang, Selangor, Malaysia

‘Faculty of Engineering, C’niversiti Pertanian Malaysia, 43400 Serdang, Selangor, Malaysia

‘Faculty of Mechanical Engineering, University of Technology Malaysia, 81300 Skudai, Johor, Malaysia

Received 29 May 1995: Accepted 10 September 1995

Abstract

A mixed plating rinse wastewater containing zinc, hexavalent chromium, trivalent chromium, and cyanide with total dissolved solids of 424 mgil was treated by a model consisting of a sand filter and ion exchange columns. A strongly acidic cation resin in hydrogen form and a strongly basic anion resin in hydroxide form were used in the columns as cationic and anionic exchangers, respectively. The cationic and anionic exchangers were regenerated by using 2% H,SO, and 5% NaOH, respectively. A 100% removal of zinc, total chromium, hexa- valent chromium and trivalent chromium was achieved in the studies. Very high removal of total dissolved solids, cyanide and hardness level was achieved at 98.9%, 99.9% and 96.5%, respectively. The conductivity of wastewater was reduced from an average of 358 psicm to 5 psicm. The case study has shown that treatment systems using cationic and anionic resin were able to treat a mixed plating bath effluent to comply with the standard discharge under the Malaysian Environmental Quality (Sewage and Industrial Effluents} Regulation, 1979.

Keywor&: Removal; Heavy metal; Plating; Rinse wastewater; Ion exchange

1. Introduction

In Malaysia, hundreds of tons of wastes and

by-products are generated annually from industri-

al sources. The toxic and hazardous wastes are of great concern to many of us. The predicted gen- eration of toxic and hazardous wastes in 1992 is

*Corresponding author.

337,000 tons annually, corresponding to 215,000 m3/y [ 11. About 29% of the toxic and hazardous wastes are from the metal finishing industries. Therefore, effluent from the plating factories must be properly treated so as not to cause more damage to the environment.

The effluent from electroplating industries contains heavy metals such as copper, zinc, nick- el, cadmium, lead and chromium as well as acids, alkalis and cyanide [2]. All these substances are

001 I-9164/96/$1.5.00 Copyright 0 1996 Elsevier Science B.V. All rights reserved.

PfI SOOll-9164(96)00139-7

420 N. Sapari et al. / Desalination 106 (1996) 419-422

highly toxic and have been regulated under the Malaysian Environmental Quality Act of 1974

[31. The objective of the project is to treat the

effluent to a standard so that the industries can reuse the water after treatment.

2. Methodology

A laboratory-scale treatment system was set- up at a metal finishing factory in Hang, Selan- gor, using a mixed-rinse plating effluent. The model treatment for the effluent from the plating process at the factory is shown in Fig. 1.

Wastewater composite samples were collected from two sources, viz rinse water after zinc plat- ing and rinse water after chromating. The raw effluent was mixed and analyzed, and the com- position is shown in Table 1.

DRAVITY

Table I Characteristics of mixed plating rinse effluent

Parameter Concentration (or corresponding unit)

PH 6.63 Conductivity, @cm 249 Total dissolved solids, mg/l 424

Hardness (as CaC03) 63.76 Zinc, mg/l 7.36

Cyanide, mg/l 5.55

Total chromium, mgil 8.25

Hexavalent chromium, mg/l 7.77

Iron Not detected

Manganese Not detected Flow rate, m3id 61.7

The set-up of the treatment model is shown in Fig. 1. The raw effluent was fed at 5 ml/min through a gravity sand filter to remove suspended

FILTRATE

STORAGE

TANK

A IONI

ii

E CHA GER

WASTED

-ER;NT 4 ,7:~ii%;~r r +

Fig. 1. Ion exchange experimental set-up.

N. Sapari et al. / Desalination IO6 (1996) 4I9-422 421

solids, then through a 50 ml cationic ion ex- changer to remove positive ions. Finally, it was passed through a 50 ml anionic ion exchanger to adsorb the negative ions. The sand filter used was a 4.5 1 tank consisting of layers of gravel and sand,

Amberlite IR- 120 and Dowex 2-X4 were used as the cation and anion exchanger, respectively. The regenerant chemicals used for the study were 2% H,SO, and 5% NaOH for the cationic and anionic exchanger, respectively.

IIH Iznl ICrcs+)l 8

CATIONIC RESIN

BREAKTHROUGH CURVE / ” ’

pH, Zn And Cr(3+) I

i P” I 6 - 5 1 ~4

IZnl -3

0 50 100 150 200 250 300

BED VOLUME

3. Results

Some results showing the breakthrough curves are shown in Fig. 2. The performance of the sys- tem was assessed in terms of metal removal. Tables 2 and 3 show the results for the experi- mental runs. Table 4 summarizes the final results showing efficiency of the system.

It was found that the ion exchange system has managed to treat and purify the effluent to a very high standard. A 100% removal for zinc, chromium 3+ and 6-t were obtained. Up to

_.~ _______ __.._--

. . _.,‘-.;, - --. ANIONIC RESIN_

\ BREAKTHROUGHCURVE

pH And CN(-)

i --._. ---t ICN]

I

200 300

BED VOLUME

400

Fig. 2. Breakthrough curves.

Table 2 Characteristics of influent

Parameter Run 1 Run 2 Run 3 Run 4 Run 5 Run 6

25

20

15

10

5

0

500

PH 6.82 6.43 8.40 6.25 7.15 7.15

Conductivity 523 286 351 299 346 345 Hardness 90 76 84 78 78 70

TDS 432 270 334 266 224 253

Cn (I-) 5.47 4.64 26.00 7.02 4.07 5.93

Total Cr 12.49 9.2 11.96 13.33 10.10 17.51

Cr (6-t) 10.47 7.94 7.41 9.07 7.74 16.00

Cr (3+) 2.02 1.26 4.55 4.26 2.36 1.51

Zn (2+) 14.30 3.00 6.96 2.09 2.27 3.99

422 N. Sapari et al. / Desalination 106 (1996) 419-422

Table 3 Characteristics of effluent

Parameter

PH Conductivity Hardness TDS Cn (I-) Total Cr Cr (6+) Cr (3+) Zn (2+) Treated volume

Table 4 Removal efficiencies

Parameter lnfluent

PH 7.03 Conductivity 358 TDS 296.5 Zn 5.43 Total Cr 12.43 Cr (6+) 9.77 Cr (3+) 2.66 Cn (-1 8.86 Hardness 79.3

0

0

0 0

4.4

0 0

0

0

8.75

Effluent

7.10

4.97 3.28 0 0 0 0 0.006 2.79

Run 1 Run 2

7.81 6.27 4.88 4.00 2.75 2.35 3.0 2.3 0.00 1 0.003

Removal efficiency (%)

98.9 100 100 100 too 99.9 96.5 -_. _..__

98.9%, 96.5% and 99.9% removal were achieved

for TDS, hardness, and cyanide, respectively. The conductivity of the effluent was also reduced from 358 to 5 us/cm.

Run 3 Run 4 Run 5 Run 6

8.19 5.71 7.50 7.09 5.30 5.50 5.45 4.71 2.33 3.45 3.25 2.625 3.9 4.1 3.7 2.6 0.012 0.003 0.004 0.012 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 5.0 8.60 5.1 6.1

4. Conclusions

The study showed that an ion exchange sys- tem can treat and purify the plating effluent to a very high standard. A 100% removal for zinc and chromium was obtained, and up to 98.9%, 96.5% and 99.9% removal was achieved for TDS, hard- ness, and cyanide, respectively, which complies with the discharge standard under the Malaysian Environmental Quality (Sewage and Industrial Effluents) Regulation, 1979.

References

Ul

PI

E31

Department of Environment, Malaysia, Environ- mental Quality Report 1990, 1991. R.A. Rahman and S. Surif, Metal finishing wastewater: characteristic and minimisation, in: Waste Management in Malaysia, B.G. Yeoh et al., eds., 1993, pp. 3-7. Government of Malaysia, Environmental Quality (Sewage and Industrial Effluents) Regulations, P.U.(A)lZ, 1979.