טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentRaize Ofer
SubjectRemoval of Heavy Metals from Water and Wastewater by
Biosorption to Brown Marine Algae
DepartmentDepartment of Civil and Environmental Engineering
Supervisors Professor Emeritus Shmuel Yannai (Deceased)
Professor Emeritus Yerachmiel Argaman (Deceased)


Abstract

Biosorption of heavy metals from aqueous solutions is a relatively new technology for the treatment of wastewater. The metallic cation sorption capacities of a few species of marine macroalgae, commonly known as brown algae, were found to be much higher than those of other types of biomass, activated carbon, natural zeolite, and were comparable to those of some synthetic ion-exchange resins. In the present study, the heavy metals (Cd, Ni, Pb, Cu, Zn) removal potential from water and wastewater of non-living brown marine macroalgae (Sargassum vulgaris and Padina pavonia in their natural form) was investigated. Both algae exhibited high metal uptake capacities (0.6 to1mmol Metal/gr). The equilibrium data for both algae fitted well to Langmuir and Hill models adsorption isotherm. In the presence of organic matter, suspended solids and calcium ions in the wastewater both species of algae showed minor decreases in their metallic cation  sorption capacities. Sargassum vulgaris showed a good lead removal capacity in Packed Bed continuous flow system (500 bed volumes). From different analytical techniques, e.g  XPS, EDS and FTIR, it appears that the main metal binding chemical groups in the algal cell wall were: carboxyl, amino, sulfhydryl and sulfonate, which occur in certain polysaccharides, proteins and peptidoglycans. The main metal sequestration mechanisms by the algal biomass were ion exchange, chelation, and precipitation on the cell wall matrix, and in the case of lead also redox reactions. The economic feasibility of the suggested biosorption process was estimated. The algae-based biosorbents cost was US $ 3.57 kg dry matter (50-90% lower than that of some commercial synthetic ion exchange resins.