Insight into Iron(III)-Tannate Biosorbent for Adsorption Desalination and Tertiary Treatment of Water Resources

An innovative biosorbent-based water remediation unit could reduce the demand for freshwater while protecting the surface and groundwater sources by using saline water resources, such as brine, brackish water, and seawater for irrigation. Herein, for the first time, we introduce a simple, rapid, and cost-effective iron(III)-tannate biosorbent-based technology, which functions as a stand-alone fixed-bed filter system for the treatment of salinity, heavy-metal contaminants, and pathogens present in a variety of water resources. Our approach presents a streamlined, cost-efficient, energy-saving, and sustainable avenue for water treatment, distinct from current adsorption desalination or conventional membrane techniques supplemented with chemical and UV treatments for disinfection. The proof of feasibility for effective treatment of heavy metals, adsorption desalination, and cleansing of pathogens is demonstrated using synthetic water, brine, and field-collected seawater. The adsorption equilibrium and adsorption kinetic isotherm models, and mass transfer diffusion models confirmed the sorbent's function for sieving heavy-metal ions-silver (Ag⁺), cadmium (Cd²⁺), and lead (Pb²⁺)-from water. The maximum adsorption capacities (<i>q</i> _m) of the sorbent for Ag⁺, Cd²⁺, and Pb²⁺ reach 96.25, 66.54, and 133.83 mg/g at neutral pH. The sorbent's affinity for heavy-metal-ion adsorption significantly increased, yielding <i>q</i> _m of 116.57 mg/g for Ag⁺, 104.04 mg/g for Cd²⁺, and 165.66 mg/g for Pb²⁺, at pH 9, respectively, due to the sorbent's amphoteric nature. The pristine sorbents exhibit exceptional adsorption desalination efficacy (>70%) for removing salinity from brine and seawater, promoting heterogeneous adsorption. Fe(III)-TA's ability to disinfect seawater, with 67% efficacy over a very short contact time (∼15 min), confirms its remarkable antimicrobial properties for contact active mode pathogens cleansing. By preventing the release of salts, heavy-metal contaminants, and pathogens into the environment, our results proved that this novel multiplex biobased sorbent approach directly contributes to the water quality of surface and groundwater resources.