PHOSPHATE ADSORPTION ON MANGANESE AND lORN OXIDES AND ACID - LEACHED SEDIMENTS FROM THE CONTINENTAL SHELF OF EG.YPT.

PHOSPHATE ADSORPTION ON MANGANESE AND lORN

OXIDES AND ACID – LEACHED SEDIMENTS FROM THE

CONTINENTAL SHELF OF EG.YPT.

A.I. BELTAGY, M.A. EL..,.SAYED, M.A. EL-SABROUTI*
AND Y. HALIM*.

Institute of Oceanography and Fisheries, Alexandria, Egypt.

* Department of Oceanography, Faculty of Science, Alexandria, Egypt.
ABSTRACT
Experiments .re designed to ascertain the respective role ot’
the three sediment c~nents:. iron oxide, manganese oxide and
other mineral constituents on phosphate ion removal from sea water
under different conditions. The results showed that the adsorption
capacity of Fez03′ 15 1.5 to’ 4.0 times ‘that of the acid treated
sediments. Manganese dioxide adsorbs Z.O to 4.5 times the amount
absorbed by acid leached sediments. Several factors affect the
adsorption process of phosphate on both oxides and other sediment
constituents.
The hydrogen ion concentration seems to be the most important
factor. Maximum adsorption Occurs at pH range between 6 and 8;
it ceases to occur below pH Z and above pH 11. Concentration of
phosphate ion in solution also affects the rate of reaction. Salinity
variations within the range of 27l1;0 to 3910 do not affect the
adsorption of phosphate by Fe203’ Mn02 or other mineral constituents
to any notable degree. It is suggested that most of phosphate ions
are removed. from the Nlle waters before it reachs the sea. Areal
steady state equilibrium between phosphate ions in solution and
phosphate ions adsorbed on both FeZ03 arid MnOZ 15 not reached in·
a short time intervals, but requires probably several hundreds
of days.