Abstract
Mixing the Scenedesmus species with nanoclay and immobilizing in sodium alginate was evaluated as a sustainable treatment method for removing nitrate, atrazine, and metals from groundwater. Gel beads containing the hybrid mixture removed 100% of 10 mg/L N nitrate and 98% of 100 µg/L atrazine from synthetic groundwater in three days. The optimal amount of nanoclay was found to be 0.30 mg per bead. The experimental data fit well into a Freundlich adsorption isotherm and followed pseudo first-order kinetics. When tested in actual groundwater, 91% of nitrate and 100% of Cr, Se, and V were eliminated in three days without need for any nutrients or carbon source. Immobilizing algal beads embedded with nanoclay is a natural, low-cost alternative for groundwater treatment. The gel beads can be reused for at least two cycles without a compromise in performance. They are water-insoluble, easy to harvest, and offer high removal efficiency.
Highlights
Groundwater in rural area is suffering from the overuse of nitrogen-based fertilizers and herbicides
The calcium–alginate beads embedded with nano zero valent iron (NZVI), magnetite nanoparticles (MNP), and powdered activated carbon (PAC) were used for nitrate removal from groundwater
The nitrate uptake capacity of the hybrid system is quantified based on different uptake mechanisms of adsorption, biological assimilation, and extracellular enzyme activity resulting from toxicity
Summary
Groundwater in rural area is suffering from the overuse of nitrogen-based fertilizers and herbicides. Several studies have been performed to evaluate the capability of immobilized algal beads in removing nutrients from aqueous solutions. The immobilized beads were able to remove 90% of the nitrate from groundwater in two days [12]. The calcium–alginate beads embedded with nano zero valent iron (NZVI), magnetite nanoparticles (MNP), and powdered activated carbon (PAC) were used for nitrate removal from groundwater. Several studies explored the application of nanoclay as an adsorbent for nitrate and atrazine removal. A mixture of algae (S. sp.) and positively charged nanoclay particles, immobilized on alginate gel (hybrid biological adsorption system), are evaluated for the removal of nitrate and atrazine from synthetic and actual groundwater. Because of its high surface area, nanoclay accelerates the adsorption of nitrate and atrazine from the bulk solution and results in a faster removal rate. The nitrate uptake capacity of the hybrid system is quantified based on different uptake mechanisms of adsorption, biological assimilation, and extracellular enzyme activity resulting from toxicity
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