76 Figure 3.7 Removal of spiked pharmaceutical compounds (2 M each) during electrolysis of (a) latrine wastewater and (b) secondary wastewater at NAT/AT. 146 Figure 4.S32 Ferrate(IV/V) oxidation experiments with O3 during electrolysis to form ferrate(VI) (full set of images).
Background and Motivation
In electrochemical processes, treatment is achieved by reactions with the oxidizing species (e.g. hydroxyl radicals, free chlorine and ozone) generated at the anode, and in some cases also by direct electrolysis on the electrode surface. Electrodes that do not rely on the use of platinum group metals are essential for reducing capital costs.
Thesis Organization
Investigation of generation kinetics and stability and speciation of the formed iron species indicated NAT/AT as a potential alternative to the conventional and expensive BDD electrodes. In all works described in the above chapters, the removal of NH4+ from latrine wastewater was very difficult using both NAT/AT and BDD.
Abstract
Introduction
Yang et al.17 used NAT anodes to electrochemically oxidize organic compounds in water (e.g., phenol) and reported that O3 produced during electrolysis enhanced the oxidation of target compounds. However, a nickel-doped AT oxide electrode can oxidize water to O3 along with ·OH at high current density.
Materials and Methods
Dissolved O3 was measured using the indigo method.21 Headspace O3 concentrations were determined using an ambient ozone monitor (Horiba APOA-360). The mass transfer rate constant for NAT/AT was determined using the limiting current technique.22.
Results and Discussion
As shown in Figure 2.4a, the heterojunction NAT/AT electrode produced the fastest BA transformation rate followed by single layer anodes, NAT and AT. The approximate rate constant for CBZ degradation (normalized by specific surface area) was calculated to be kCBZ,SA m/s (Figure 2.S16).
Conclusions
The total concentrations of trihalomethanes (THMs) and haloacetic acids (HAAs) after 90 minutes of electrolysis were 0.007 and 65 µg/L, respectively. Overall, lower concentrations of ClO3- (1.7 mM) and ClO4- (0.16 mM) were observed at 90 min of electrolysis on NAT/AT anodes compared to BDD ([ClO3-]90 min = 5 mM, [ClO4 -]90 min = 0.5 mM) operated at the same current density and [electrode area]/[electrolyte volume] ratio by our group.34 The minimal DBP formation observed in this study is due to pathogens and drugs readily was removed before the chlorination breakpoint.
Acknowledgments
Displacement of Reactive Species in Sb-SnO2- Electrocatalyzed E. Coli Inactivation and Phenol Degradation: Effects of Nickel and Electrolyte Doping. An overview of technology used to remove trihalomethane (THM), trihalomethane precursors, and trihalomethane forming potential (THMFP) from water and wastewater.
Supporting Information
A laser photolysis study of the reaction of sulfate (1-) with chloride and the subsequent decomposition of chlorine (1-) in aqueous solution. Ozone formation in the reaction of hydroxyl with O3- and decay of the ozonide ion radical at pH 10-13.
Abstract
Ozone- and hydroxyl radical-mediated oxidation of pharmaceutical compounds by Ni-doped Sb-SnO2 anodes: degradation kinetics and transformation products. A similar trend in the treatment efficiency is observed for mixtures of CBZ and FCZ with other pharmaceutical compounds in toilet wastewater and secondary wastewater of ČN.
Introduction
In our previous study, a heterojunction Ni-Sb-SnO2 anode (NAT/AT) was prepared, which simultaneously produces ozone (O3) and hydroxyl radical (·OH) at the anode.23 NAT/AT electrolysis has been shown to be effective for the treatment of mixt. of pharmaceutical compounds in toilet wastewater. Since aromatic rings and/or N and S atoms with unpaired electrons are ubiquitous in pharmaceutical compounds, NAT/AT electrolysis should prove effective for the treatment of pharmaceuticals in wastewater. For carbamazepine (CBZ) and fluconazole (FCZ), the kinetics of degradation and the formation of transformation products (TP) are investigated in detail.
Materials and Methods
Carbamazepine (CBZ), fluconazole (FCZ) and other pharmaceutical compounds were quantified using high-performance liquid chromatography coupled with a UV detector (HPLC-UV) and equipped with an XDB-C18 column (ZORBAX, 2.1 50 mm, 1.8 m particles). Eluent flowed at 0.4 mL/min and consisted of acetonitrile (ACN) and water with 0.1% formic acid. Products were monitored under positive electrospray ionization (ESI+) in resolution mode (measurement accuracy better than 1 ppm RMS) with 0.2 kV capillary voltage.
Results and Discussion
In NaClO4, pH had a negligible effect on FCZ removal for NAT/AT and BDD (Figure 3.S4). In the case of BDD electrolysis, the product with the highest response was TP208 with an intensity that peaked at 0.5 min (Figure 3.5b). The individual degradation kinetics of ATL, GBP, and IBP by NAT/AT and their kinetic modeling predictions are shown in Figure 3.S15.
Conclusions
Acknowledgments
Transformation of oxcarbazepine and human metabolites of carbamazepine and oxcarbazepine in wastewater treatment and sand filters. Kinetics and mechanism of aqueous degradation of carbamazepine by heterogeneous photocatalysis using nanocrystalline TiO2, ZnO and multiwalled carbon. Synergistic effect between UV and chlorine (UV/chlorine) on the degradation of carbamazepine: influencing factors and radical species.
Supporting Information
However, most of the observed difference in [O3] should come from the different O3 production at NAT/AT. To further investigate the transformation pathways in the NAT/AT and BDD system, electrolysis of 20 μM TP253b (CBZ-EP) standard was performed. Their formation using radiation pulses and their role in the mechanism of the Fricke Dosimeter.
Additional Notes
New synthesis routes for highly oxidative iron species: generation, stability and treatment applications of ferrate (IV/V/VI).
Abstract
Introduction
More recently, evidence of circumneutral ferrate electrosynthesis has been reported using BDD electrodes and Fe2+/Fe3+ precursors for water treatment applications23–29. Another group of promising materials are substoichiometric alternatives to platinum group metal oxides, known as Magnéli phase titanium oxides (TinO2n-1, 4 ≤ n which also possess very favorable electrocatalytic properties for water treatment and ferrate synthesis. The study also includes oxidation kinetics, oxidant. stability and speciation , as well as application for water treatment purposes, providing a potentially powerful alternative to conventional and expensive BDD electrodes and wet chemical synthesis processes for conventional ferrate(VI) generation.
Materials and Methods
In this study, the circumneutral electrosynthesis of ferrates was investigated using a heterojunction of NAT and AT electrodes. To date, no circumneutral electrosynthesis of ferrates has been performed with any electrode other than BDD. In this study, we highlight the successful generation of ferrates, including the first report of the circumneutral electrosynthesis of strong ferrate(IV) and ferrate(V) species in the intermediate state using these MMO and BDD materials.
Results and Discussion
For all anode materials, evidence of ferrate formation was observed using the ABTS quantification method (see Supporting Information Figure 4.S2-S12 for all ABTS absorption data). Similar to the BDD-derived ferrate solution, rapid degradation was observed in the first 20 seconds (see Supporting Information Figure 4.S22), with absolute CBZ removal much less than BDD due to the significantly lower initial concentration of ferrate (IV/V). All CVs for both the NAT and BDD produced ferrates can be found in the Supporting Information (Figures 4.S29 and 4.S30).
Acknowledgments
Based on the control experiments, as well as previous research that found ozone to have a small reaction rate coefficient with Cl- to form RCS67, the primary mechanism of ferrate(VI) generation was determined to be by ozone oxidation. These intermediate state ferrate species were found to be more oxidative towards persistent organic pollutants, which are recalcitrant to ferrate(VI) oxidation. Finally, a key mechanism for ferrate(VI) electrosynthesis using the NAT electrode was proposed, which was identified to be attributed to simultaneous ozone oxidation of Fe 3+ , demonstrating two new reaction pathways for ferrate(VI) generation.
Advances in the development and use of ferrate (VI) salt as an oxidant and coagulant for water and wastewater treatment. Circumneutral Ferrate Oxidant Electrosynthesis: An Emerging Technology for Small, Remote, and Decentralized Water Treatment Applications. Enhanced oxidative transformation of organic pollutants by ferrate(VI) activation: possible involvement of FeV/FeIV species.
Supporting Information
The produced ferrate (IV/V/VI) BDD and NAT solutions were analyzed using Raman spectroscopy (Renishaw inVia Qontor) to determine whether the different ferrate species (e.g., Fe(IV), Fe(V) and/or Fe(VI) ) could be identified. BDD and NAT-produced ferrate (IV/V/VI) solutions were also analyzed using FTIR spectroscopy (Thermo Scientific Nicolet iS50) to determine whether different ferrate species (e.g., Fe(IV), Fe( V) and/or Fe( VI)) could be identified.
Abstract
Introduction
To address the challenges of current urinary nitrogen recovery techniques, here we report an integrated decentralized treatment platform for nitrogen recovery from fresh urine that can avoid long-term spatial storage of urine and minimize nitrogen loss during this process (Scheme 1). To accomplish many tasks in the proposed fresh urine treatment, we (i) selected a waterproof and porous zirconia metal–organic framework MOF-808, (ii) took advantage of the high modularity of this material, and (iii) designed and synthesized a series of functional MOF-808 specifically for the purpose of extracting nitrogen from fresh urine. OA and MOF-808-Cu were then effectively incorporated into the fresh urine treatment process, and 75% nitrogen removal and 45% recovery efficiency were achieved in just 30 minutes.
Results
With materials in hand, we examined the ammonium absorption performance of the four MOF-808-based adsorbents. MOF-808-OA could be reused for at least 10 cycles while maintaining its ammonium capture capacity. While the blue color (top) indicated significant ammonium generation by MOF-808-U, the color change to green (bottom) demonstrated significant ammonium removal by MOF-808-OA.
Discussion
Selective recovery of ammonia nitrogen from wastewater with transition metal-loaded polymeric cation exchange adsorbents. Removal and Recovery of N, P and K from Urine via Ammonia Syrup and Precipitations of Struvite and Struvite-K. Electrochemical ammonia recovery from source-separated urine for microbial protein production. MOF-808: A metal-organic framework with intrinsic peroxidase-like catalytic activity at neutral PH for colorimetric biosensing.
Supporting Information
MOF-808-no FA: MOF-808-no FA was synthesized as an intermediate for dicarboxylate incorporation. MOF-808-OA: MOF-808-no FA was added to an aqueous solution of sodium oxalate (OA) and stirred at room temperature for 2 days. The free urea solution was then added to the separate MOF-808-U to measure the immobilized urease activity the next day.
