Cobalt–nickel mixed oxide surface: A promising adsorbent for the removal of PR dye from water

A mixed oxide of cobalt (Co) and nickel (Ni) with an approximate composition of Co0.4Ni0.4O0.2 was prepared chemically by precipitating from the corresponding metal carbonates and heating the mixture of carbonates at 650 °C under ambient atmosphere. The mixed (Co–Ni) oxide thus prepared was characterized by IR, SEM and XRD methods. The composition of the mixed metal oxide was obtained by EDX analysis. The surface behavior of the Co–Ni mixed oxide matrix was tested by adsorption studies and pHpzc measurement. The Co–Ni mixed oxide matrix behaves as a charged adsorbent at the pH media higher and lower than its pHpzc value (9.50) and thus found to be capable of anchoring the oppositely charged species onto its surface. Removal of cationic and anionic dyestuffs, viz., methylene blue (MB) and procion red (PR), respectively, was attempted using the mixed oxide surface as adsorbent. Although both the dyes can be removed by the mixed oxide, the extent of PR removal (∼70%) seems to be much higher than that of MB (∼20%) demonstrating the superior performance of the Co–Ni mixed oxide for its use as adsorbent in removing the anionic PR dyestuff from water.