Country of application:
Electrochemical Process for Metal Ion Recovery from Wastewater
Country of application:
UAE
Scope of innovation
☐ Office work
☒ Production / Service supply process
Sector-specific
☐ Yes / please, specify sector(s):
☒ No (relevant for all sectors)
Description of the needs
Using activated carbon derived from date seeds, a common waste product of the date fruit industry in the UAE, and a nitrogen-containing compound called polyaniline, the team developed an electrode that could be used to sustainably recover and reuse metal ions from mining industry wastewater.
When rocks containing sulfide materials are exposed to air and water — often through mining — they undergo oxidation, producing sulfuric acid and dissolved iron. This acid can further dissolve other heavy metals such as copper, zinc, and lead present in the surrounding rock. These heavy metals can cause environmental damage if the wastewater is discharged without treatment. Prof. Banat points to the impact on waterways in particular: The high concentrations of iron and copper affect the smell, color, and oxygen balance of the aquatic ecosystem, killing fish and other aquatic organisms.
Description of the solution
Mining wastewater often contains a complex mixture of metal ions, organic matter, and other contaminants, making it difficult to selectively recover and separate specific metal ions for reuse without also extracting unwanted impurities. Plus, the presence of multiple metal ions and other substances may interfere with the recovery process, leading to reduced efficiency and selectivity. Traditional methods are also limited by their robustness in varying wastewater conditions (frequent regeneration of replacement of the adsorbent material is time-consuming and costly) and their generation of secondary contaminants. Finally, once metal ions have been recovered using conventional techniques, they need to be further processed and purified before they can be reused. This can involve additional steps, which may be complex and resource-intensive.
Prof. Banat’s team thinks capacitive deionization (CDI) is the answer. CDI is an electrochemical water-treatment technique. The process operates by electrosorption of ions on the surface of electrodes. When a voltage is applied between the two electrodes, the positive electrode attracts negatively charged ions (anions), while the negative electrode attracts positively charged ions (cations). As the ions approach the surface of the respective electrodes, they undergo electrosorption, where they accumulate at the electrode surface due to the electrostatic forces between the electrode and the ions. There they remain until the voltage is reversed or stopped.
By continuously cycling the applied voltage, the CDI process allows for the removal of ions from water without chemical additives or membranes, making it a promising technology for desalination, water softening, and water purification.
Description of the effect
The ideal electrode material for CDI applications has many features: It should have a large specific surface area for ion adsorption; exhibit high adsorption capacity, meaning it can attract and retain a significant amount of ions from the water; offer faster electrosorption kinetics for more efficient and quicker ion removal; have rapid conductivity to facilitate the movement of ions and ensure efficient charge transfer and overall performance; and be chemically stable to withstand the conditions and maintain its performance over time.
Carbon-based materials, including nitrogen-doped activated carbons, meet most of these requirements. Nitrogen doping in activated carbon enhances CDI performance through several mechanisms including the introduction of surface functionalities to enhance the overall ion adsorption capacity and increasing the charge density, which promotes the charge-transfer process during electrosorption. The presence of nitrogen also changes the structure of the carbon matrix, creating distortions that facilitate deeper ion access and charge accumulation.
Nitrogen sources such as ammonia, nitric acid, and polyaniline (PANI) have been used to synthesize nitrogen-doped carbon materials for CDI applications. PANI, in particular, contains amine and imine functionalities that significantly enhance the electrochemical adsorption of metal ions from wastewater.
The CMAT/CeCaS researchers used a material called polyaniline decorated date seed-derived activated carbon (PANI-DSAC), a composite of polyaniline and activated carbon made from date seeds. The seeds are a byproduct of the date fruit industry, which often generates a large amount of waste. Utilizing the seeds as raw material for activated carbon helps reduce this waste and promote sustainable resource management.
Company/companies that developed/implemented/offer the innovation
The internationally top-ranked Khalifa University of Science and Technology is the one university in the UAE with the research and academic programs that address the entire range of strategic, scientific and industrial challenges facing the UAE’s knowledge economy transformation and our rapidly evolving world.
Its world-class faculty and state-of-the-art research facilities provide an unparalleled learning experience to students from the UAE and around the world. The university brings together the best in science, engineering and medicine in the UAE, to offer specialized degrees that can take promising high school graduates all the way to top-rated doctorate degree holders.
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