Sustainable and simplistic green Ag°/Agar as an efficient, durable and stable solid formula for removing wastewater pollutants

Silver nanoparticles (Ag°) were greenly synthesized using Hordeum vulgare L. water extract and immobilized on agar to obtain a solid Ag°/Agar formula. Hence, its catalytic potential for removing pollutants was investigated. Characterization of the Ag° and their solid formula was performed using UV-Vis spectroscopy, FTIR, EDX, and SEM analysis. The results showed that each gram of the synthetized formula contained 2.6 ng Ag° which represents the active ingredient responsible for the removal process. Applying the formula at a 10% (w/v) ratio was sufficient for achieving nearly 95% removal of 500 mg/L of methylene blue (MB). The presence of 20 mM CaCl2 resulted in a 7% decreased in Ag°/Agar removal efficiency. The desorption study illustrates that less than 5% of sorbed MB was released from presented formula after 24 h of the desorption process. The formula was succeeded to remove MB for nine consecutives cycles of free salt aqueous solutions, and for five runs in the presence of 20 mM CaCl2 salt, even without conducting any regeneration process. The sorption data fitted well to the pseudo- second order kinetic and Langmuir isotherm model. The rate constant value equals 0.206 g / mg min, and the maximum adsorption capacity of the presented Ag°/Agar formula (2.6 ng Ag°) was 6.219 mg /g. This work develops a simplistic, green, and solid-state from ultra-low nano silver content formula that addresses the stability issues of liquid-phase silver catalysts.