Heavy metal cation retention by unconventional sorbents (red muds and fly ashes)

Pergamon

PII: S0043-1354(97)00204-2

IVat. Res. Vol. 32, No. 2, pp. 430-440, 1998

© 1998 Elsevier Science Ltd. All rights reserved

Printed in Great Britain

0043-1354/98 $19.00 + 0.00

HEAVY METAL CATION

UNCONVENTIONAL SORBENTS

ASHES)

RETENTION BY

(RED MUDS AND FLY

RE,AT APAK*, ESMA TOTEM, MEHMET HLIGI]L and JI]LIDE HIZAL

Department of Chemistry, Faculty of Engineering, Istanbul University, Avcdar, 34850, Istanbul,

Turkey

(First received April 1996; accepted in revised form June 1997)

Al~raet--Toxic heavy metals, i.e. copper (II), lead (II) and cadmium (II), can be removed from water

by metallurgical solid wastes, i.e. bauxite waste red muds and coal fly ashes acting as sorbents. These

heavy-metal-loaded solid wastes may then be solidified by adding cement to a durable concrete mass

assuring their safe disposal. Thus, toxic metals in water have been removed by sorption on to inexpen￾sive solid waste materials as a preliminary operation of ultimate fixation. Metal uptake (sorption) and

release (desorption) have been investigated by thermostatic batch experiments. The distribution ratios

of metals between the solid sorbent and aqueous solution have been found as a function of sorbent

type, equilibrium aqueous concentration of metal and temperature. The breakthrough volumes of the

heavy metal solutions have been measured by dynamic column experiments so as to determine the sat￾uration capacities of the sorbents. The sorption data have been analysed and fitted to linearized adsorp￾tion isotherms. These observations are believed to constitute a database for the treatment of one

industrial plant's effluent with the solid waste of another, and also to utilize unconventional sorbents,

i.e. metallurgical solid wastes, as cost-effective substitutes in place of the classical hydrous-oxide-type

sorbents such as alumina, silica and ferric oxides. © 1998 Elsevier Science Ltd. All rights reserved

Key words---cadmium (II), lead (II), copper (II), sorption, red muds, fly ashes

INTRODUCTION

Cadmium (II), lead (II) and copper (II) are well￾known toxic heavy metals which pose a serious

threat to the fauna and flora of receiving water

bodies when discharged into industrial wastewater.

In spite of strict regulations restricting their careless

disposal, these metal cations may still emerge in a

variety of wastewaters stemming from catalyst, elec￾trical apparatus, painting and coating, extractive

metallurgy, antibacterials, insecticides and fungi￾cides, photography, pyrotechnics, smelting, metal

eleetroplating, fertilizer, mining, pigments, stabil￾izers, alloy industries, electrical wiring, plumbing,

heating, roofing and building construction, piping,

water purification, gasoline additive, cable covering,

ammunition and battery industries (Buchauer, 1973;

Low and Lee, 1991; Periasamy and Namasivayam,

1994) and sewage sludge (Bhattacharya and

Venkobachar, 1984). The acute toxicity of these

heavy metals have caused various ecological cata￾strophes in human history, such as the "itai-itai"

disease due to cadmium (Riley and Skirrow, 1975).

Prolonged effect may cause other chronical dis￾orders (Huang and Ostovic, 1978).

*Author to whom all correspondence should be addressed.

Various treatment technologies have been devel￾oped for the removal of these metals from water.

The hydrometallurgical technology extracts and

concentrates metals from liquid waste using any of

a variety of processes, such as ion exchange, electro￾dialysis, reverse osmosis, membrane filtration,

sludge leaching, electrowinning, solvent stripping,

precipitation and common adsorption (LaGrega et

al., 1994a).

Both powdered (Sorg et al., 1978) and granular

activated carbon (Huang and Smith, 1981) have

been used for the adsorptive removal of Pb, Cd and

similar "soft" heavy metals, especially when associ￾ated with common organic particulate matter in

water. Activated carbon from cheaper and readily

available sources, such as coal, coke, peat, wood,

nutshell (Freeman, 1989) and rice husk (Srinivason,

1986), may be successfully employed for the

removal of heavy metals from aqueous solutions.

Hydrous oxides such as alumina, iron oxides

(hematite and goethite) (Cowan et al., 1991; Gerth

and Bruemmer, 1983) manganese (IV) oxide

(Hasany and Chaudhary, 1986) and titanium (IV)

oxide (Koryukova et al., 1984) have also been used

for the adsorption of the indicated heavy metals.

The cost of the adsorptive metal removal process

is relatively high when pure sorbents (either acti￾430