| Summary: |
Nowadays, it is well known that heavy metals escaping into the environment pose a serious threat to human health and other living beings, as they accumulate in living tissues throughout the food chain (Fig. 1). The Decision No 2455/2001/EC of the European Parliament established a list of priority substances in the field of water policy, where toxic metals are included. The currently available best treatment technologies for trace-metal-bearing effluents are either not effective enough or are prohibitively expensive, considering the large quantities of produced wastewaters (Fig. 2). Biosorption uses biological materials, which are abundant in nature, such as seaweeds and agricultural wastes, to concentrate and immobilize heavy metals. The efficiency of the biosorption process for removal of metals is comparable to the ion exchange treatment even for low pH and high salinity. Effluents with metal ion concentrations in the order of ppb can be achieved using biosorption. While commercial ion exchange resins are rather costly, the price tag of biosorbents can be one tenth of that of the resin. Additional cost reduction results from the possible heavy metals recovery.
The main goal of the ALGAEVALUE project is to study the problems related with the environmental decontamination of persistent toxic metals present in real industrial effluents from different origins: metal processing, leather tanning, metal plating etc., by biosorption onto brown macro-algae from Portuguese coast (Figs. 3 and 4). The present project is intended to pursue and expand previous studies developed in the project Recycling of metal contaminated waters by biosorption on to marine algal biomass and industrial algal wastes, ref. POCI/AMB/57616/2004, and further works performed by two post-doc and two Ph.D. students. The information gathered in the project led to some main conclusions regarding the application of biosorption technology: the brown algae selected from the Portuguese Coast, after a pr  |
Summary
Nowadays, it is well known that heavy metals escaping into the environment pose a serious threat to human health and other living beings, as they accumulate in living tissues throughout the food chain (Fig. 1). The Decision No 2455/2001/EC of the European Parliament established a list of priority substances in the field of water policy, where toxic metals are included. The currently available best treatment technologies for trace-metal-bearing effluents are either not effective enough or are prohibitively expensive, considering the large quantities of produced wastewaters (Fig. 2). Biosorption uses biological materials, which are abundant in nature, such as seaweeds and agricultural wastes, to concentrate and immobilize heavy metals. The efficiency of the biosorption process for removal of metals is comparable to the ion exchange treatment even for low pH and high salinity. Effluents with metal ion concentrations in the order of ppb can be achieved using biosorption. While commercial ion exchange resins are rather costly, the price tag of biosorbents can be one tenth of that of the resin. Additional cost reduction results from the possible heavy metals recovery.
The main goal of the ALGAEVALUE project is to study the problems related with the environmental decontamination of persistent toxic metals present in real industrial effluents from different origins: metal processing, leather tanning, metal plating etc., by biosorption onto brown macro-algae from Portuguese coast (Figs. 3 and 4). The present project is intended to pursue and expand previous studies developed in the project Recycling of metal contaminated waters by biosorption on to marine algal biomass and industrial algal wastes, ref. POCI/AMB/57616/2004, and further works performed by two post-doc and two Ph.D. students. The information gathered in the project led to some main conclusions regarding the application of biosorption technology: the brown algae selected from the Portuguese Coast, after a pre-treatment, can accumulate metal ions 25% in excess of its dry weight; the process presents low sensitivity to environmental (pH and salinity) and impurity factors; ion exchange was established to be the dominant biosorption mechanism; the most effective biosorption process configuration is the packed bed sorption column; the overall capacity factor to remove and concentrate the metal was higher than 600 (Fig. 5), making the eventual recovery of the metal feasible with metal concentrations in the eluate higher than 16 000 mg of metal per liter; biosorption allows significant cost savings (biosorbent price < 5 ¤/kg and possible recovery of the metals) in comparison with existing competing technology as ion exchange. Only a few studies of the biosorption process have been conducted in pilot plants and the quite scarce information with real effluents has been up to now one of the main reasons for the absence of industrial applications in this field. This project attempts to serve as a step forward in this subject.
The project will start by the characterization (physical-chemical-ecotoxicological) of the metal bearing effluents selected, in order to obtain the concentration of the different contaminants, biodegradability (Zahn Wellens test) and toxicity (Vibrio fischeri test) and the identification of the effluent preliminary pre-treatment to be done (FEUP and SPIKES & COGS). At the same time, the collection and pre-treatment of the selected brown marine macro-algae (Fig. 6) will be done (FEUP). The biosorption process (equilibrium, kinetics in batch and packed bed column) of meta |