Biosorption of Cd, Ni, and Zn with Mixtures of Different Types of Algae

Abstract

The biosorption process was studied using a mixture of three different types of algae: Codium vermilara (green), Chondrus crispus (red) and Ascophyllum nodosum (brown) as biosorbent. A preliminary study was carried out on the influence of pH and biomass concentration (the experimental values selected were 6 and 0.5 g/L, respectively), first using the algae individually and later in binary and ternary combinations. The three metals selected (Cd, Ni, and Zn) were tested in monometallic, bimetallic, and trimetallic solutions. In monometallic systems with an individual biomass, the Langmuir model predicts that the sorption uptake of the brown alga Ascophyllum nodosum is higher than that of the red alga Chondrus crispus, and this in turn is higher than that of the green alga Codium vermilara. The sequence of metal sorption was: Ni ≈ Zn >Cd. In a mixture of the three types of algae, the results indicated that metal uptake was best with the mixture Chondrus crispus + Ascophyllum nodosum. The mixture Codium vermilara + Ascophyllum nodosum behaved similarly to the ternary mixture in experiments with equal biomasses of each species and slightly better than the mixture Codium vermilara + Chondrus crispus, in both monometallic and multimetallic systems. The results suggest that biomass mixtures could be effective in the treatment of real effluents.