MERCURY REMOVAL FROM A CHLORALKALI
PLANT IN EGYPT
Ahmed Hamza, Associate Professor
Olfat Elsebai, Associate Professor
High Institute of Public Health
Alexandria, Egypt
Hamed Saleh, Associate Professor
Institute of Fish Research
Alexandria, Egypt
INTRODUCTION
Concern has been expressed recently regarding the contamination of the Mediterranean with
hazardous industrial wastes such as mercury. A major industrial user of mercury in Alexandria is the
Misr Chemical Company (MCC). Losses of mercury from the chloralkali process were believed to be
unimportant, but recent monitoring of the effluent indicated an estimated mercury emission of 10.2
kkg/y. Mercury losses at this plant are five times the acceptable level for normal operation of the
chloralkali process [1].
Mercury may occur in several forms ranging from elemental to dissolved organic and inorganic
species; however, some microorganisms have the ability to convert less hazardous organic and inorganic forms of mercury to the highly toxic methyl and dimethyl mercury [2]. Marine life concentrates
the mercury biologically, resulting in fish containing lethal amounts of methyl mercury. Ingestion of
contaminated fish led to development of Minimata disease in Japan resulting in deaths and afflica-
tion. Because of methylation and bioconcentration of methyl mercury, a maximum concentration of
0.1 j.g/1 is recommended for marine aquatic life [3].
The research described here is part of a major project sponsored by the Egyptian government to
abate pollution from hazardous industrial sources in Alexandria. The first phase involved comprehensive survey of all process effluents at the MCC and the proposed methods to limit mercury losses and
to reduce pollution. The second phase consisted of bench scale treatability studies for removal of mercury.
Earlier studies of mercury removal had indicated efficient elimination by activated carbon. However, carbon required high capital and regeneration costs and is partially effective in removing mercury from water with low organic content [4]. Mercury sorption on coal is temperature and pH dependent while high levels of calcium and chloride reduce the sorption efficiency [5]. The treatment train
used in this study consisted of pH adjustment, clay adsorption, and activated sludge biological system.
CHLORALKALIL PRODUCTION AT THE MISR CHEMICAL COMPANY
The MCC operates two major plants in Alexandria for the production of caustic soda and chlorine
by electrolysis, and the production of soda ash and caustic soda by the solvey process. The MCC produces 63000 kkg/y caustic soda, 12000 kkg/y chlorine, and 33000 kkg/y soda ash. Additional units
produce hydrochloric acid (1200 kkg/y), calcium hypochlorite (5000 kkg/y of 60 g/1 cone), and
hydrogen peroxide (370 kkg/y).
In the electrolysis process (Figure 1), chlorine is produced at the anode and hydrogen together with
caustic soda at the cathode. To manufacture pure caustic soda and to lessen clogging of the cell diaphragm with a consequent voltage increase, purification of the brine to remove calcium, iron, and
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