Biosorption of heavy metals by Laminaria japonica

Laminaria japonica, commonly called kelp, was investigated as a biosorbent for heavy metal removal. Kelp exhibited superior biosorption capacity over many natural biomaterials investigated. On the biosorbent weight basis, the biosorption capacity of kelp for heavy metal is comparable to that of the commercial ion exchange resins. The breakthrough biosorption capacity of kelp was in the range of 1.04–1.40 meq/g, while the ultimate biosorption capacity of kelp was in the range of 1.60 to 1.91 meq/g.; The complex stability and binding affinity of metal ions to kelp were in the order of Zn < Ni < Cu < Cd. The equilibrium biosorption capacity of heavy metals was in the order of Cd > Cu > Zn > Ni. The release of light metals from the biosorbent was in the sequence of K< Na < Mg < Ca. The results in this research supported that ion exchange is the principal mechanism in the biosorption of heavy metals with kelp. Both the weakly acidic carboxyl groups in alginic acids and the strong acidic sulfate groups in fucoidin contribute to provide most of exchange sites in the biosorbent kelp.; Thomas model and Hiester's solution for ion exchange was introduced to develop the mathematical model of biosorption for heavy metals Cd, Cu, Ni, and Zn with biosorbent kelp. The ultimate biosorption capacity, equilibrium constant, and reaction rate constant of kelp were determined for each tested heavy metal. The predicted effluent concentration histories matched fairly well with the experimental results in biosorption column operation. With the help of the developed mathematical model, the biosorption column operation behaviors can be predicted in practical applications. This will provide useful information for biosorption facility design and operation.; The saturated kelp can be regenerated with 1 M hydrochloric acid. The higher recovery of biosorption capacity was found when the kelp was saturated with copper and zinc. Important factors for the regeneration of kelp are adsorbed metals and concentrations, regenerant solutions, and initial biosorbent preparation method.