Biosynthesis of Silver Nanoparticles Based on <i>Senna Alata </i>and Striking Dynamization of a Ternary Fe°/S/Pz Filter Device for Electrochemical Remediation of Phosphates in Water

Abstract

Fe°/H<sub>2</sub>O systems have already proven remediation properties. Though, due to the early clogging of 100% Fe°-bed devices, the site of electrochemical corrosion products (CPs), they are associated with non-expansive porous materials such as pozzolan (Pz), and natural coal (NC), in binary (Fe°/Pz, Fe°/NC), ternary (Fe°/S/Pz, Fe°/S/NC) or quaternary configurations Fe°/S/Pz/C (Iron/Sand/Pozzolan/Natural coal), thus making the thickness of the reactive zone (RZ) dependent on the proportion of materials. A ternary Fe°/S/Pz filter system with a heterogeneous RZ, embedded between two sand layers, was enhanced with a small amount of silver nanoparticle (AgNp) based on <i>senna alata </i>(<I>SA</I>). The resulting new device was studied for an operation of its nanometric size, and its very large reactive surface, since it’s an herbaceous plant, 30 to 50 cm tall, of the <i>fabaceae</i> family, without characteristic flavor or smell, however with numerous antifungal, antibacterial and corrosion inhibitory properties. Eighteen (18) filtering devices were tested for this, including six (6) 100% Fe°, (6) 25% Fe°/50% S/25% Pz, and (6) 25% Fe°/48.75% S/25% Pz/1.25% Np. Phosphates, components of fertilizers and agricultural waste 0.2 g/L K<sub>2</sub>HPO<sub>4</sub>, at pH=5 was used as operative indicator. The experiments lasted forty (40) days per device. We measured the pH, phosphates removal rate, dissolved iron, flow rate, Conductivity and redox potential. Thus, it appears that Np <I>SA </I>in Fe°/S/Pz allow a resurgence of efficiency, such as 100% Fe° ˂ 25% Fe°/50% S/25% Pz ˂ 25% Fe°/48.75% S/25% Pz/1.25% Np. A rate of about 1% of the silver Np <I>SA </I>effectively contributes to the phosphate removal process, the thickness of the RZ is not changed, the pH is in line with WHO recommendations, the flow rate is acceptable. Although fluctuating, the measured conductivities and redox potentials are low for all devices, confirming the same oxidation degree of iron released.