Degradation of Organic Methyl Orange (MO) Dye Using a Photocatalyzed Non-Ferrous Fenton Reaction.

Removal of recalcitrant organic pollutants by degradation or mineralization from industrial waste streams is continuously being explored to find viable options to apply on the commercial scale. Herein, we propose a titanium nanotube array (based on a non-ferrous Fenton system) for the successful degradation of a model contaminant azo dye, methyl orange, under simulated solar illumination. Titanium nanotube arrays were synthesized by anodizing a titanium film in an electrolyte medium containing water and ethylene glycol. Characterization by SEM, XRD, and profilometry confirmed uniformly distributed tubular arrays with 100 nm width and 400 nm length. The non-ferrous Fenton performance of the titanium nanotube array in a minimal concentration of H2O2 showed remarkable degradation kinetics, with a 99.7% reduction in methyl orange dye concentration after a 60 min reaction time when illuminated with simulated solar light (100 mW cm-2, AM 1.5G). The pseudo-first-order rate constant was 0.407 µmol-1 min-1, adhering to the Langmuir-Hinshelwood model. Reaction product analyses by TOC and LC/MS/MS confirmed that the methyl orange was partially fragmented, while the rest was mineralized. The facile withdrawal and regeneration observed in the film-based titanium nanotube array photocatalyst highlight its potential to treat real industrial wastewater streams with a <5% performance drop over 20 reaction cycles.

Effect of Membrane Fouling on Fertilizer-Drawn Forward Osmosis Desalination Performance.

Fertilizer-drawn forward osmosis (FDFO) has garnered immense attention for its application in the agricultural field and its potential to reuse wastewater sustainably. Membrane fouling, however, remains to be a challenge for the process. This study aims to investigate the influence of membrane fouling on the performance of the FDFO process. Synthetic wastewater (SWW) and multi-component fertilizer (MCF) were used as feed solution (FS) and draw solution (DS) with cellulose triacetate (CTA) forward osmosis (FO) membrane orientation. The performance was evaluated through water flux (WF), percentage recovery and percentage of salt reject. The WF declined from 10.32 LMH (L/m2·h) to 3.30 LMH when ultra-pure water as FS was switched with concentration FS indicating the dependence of the performance on the type of FS used. Accelerated fouling experiments conducted to verify the fouling behavior showed a decline in the water flux from 8.6 LMH to 3.09 LMH with SWW and 13.1 LMH to 3.42 LMH when deionized water was used as FS. The effects of osmotic backwashing and in situ flushing as physical cleaning methods of the foul membrane were studied through water flux and salt recovery percentage. Both cleaning methods yielded a WF close to the baseline. Osmotic backwashing yielded better results by eliminating foulant-foulant and foulant-membrane adhesion. The cleaning methods were able to recover 75% of phosphate and 60% of nitrate salts. Scanning electron microscopy (SEM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) results validated the effectiveness of the methods for the physical cleaning of foul membranes. This study underlines the importance of the FS used in FDFO and the effectiveness of osmotic backwashing as a cleaning method of FO membranes.

Modeling and simulation of fertilizer drawn forward osmosis process using Aspen Plus-MATLAB model.

Although experimental studies on the impact of feed (FS) and draw solutions (DS) on the forward osmosis (FO) applications are reported in literature, systematic mathematical modeling considering the dynamic change in solution properties is lacking. In this study, asymmetric FO membrane simulation model was established using Aspen Plus-MATLAB subroutines algorithm to account for the effect of concentration polarization (CP), types of FS and DS and in their properties on FO performance. The developed model was validated by comparing the simulation with experimental results. The model successfully predict the performance of FO process under wide varieties of operational conditions, FS and DS flow rates and concentrations. The model showed that the variation of MCFDS concentration had a marked effect on water flux (WF) in contrast to flow rate. The WFs obtained from seawater (SW) increased from 5.28 L/m2.h to 42.08 L/m2.h as MCFDS changes from 150 g/L to 300 g/L which corresponding to 11.66% to 45.33% of water recovery. As for synthetic aquaculture wastewater (SAWW), 9.70 L/m2.h to 37.32 L/m2.h of WFs were exhibited with the increase of MCFDS concentration from 50 g/L to 200 g/L, respectively. The effect of concentrated external CP (CECP) was found to be significant in case of SW and negligible with SAWW. Whereas, increasing MCFDS concentration increases the severity effect of dilutive internal CP (DICP). The degree of DICP depends on the solute resistivity (KD) of porous layer, which were elevated (4.22-5.88 s/m) as MCFDS concentration increases (150-300 g/L). The study demonstrated the effectiveness and suitability of the developed Aspen Plus-MATLAB model simulating the FO process.

Influence of draw solution type and properties on the performance of forward osmosis process: Energy consumption and sustainable water reuse.

Single and multi-component fertilizers were used as a draw solution (DS) in forward osmosis (FO) to produce high-quality water from synthetic and seawater solution, eliminating the need for DS regeneration and reducing the operational energy. The effect of DS type, concentration, circulation flow rates on the FO water flux (WF), specific water flux (SWF), percentage water recovery (%Wrecovery), reverse salt flux (RSF) and percentage salt rejection (%R) were studied. The results showed that single fertilizer draw solution (SFDSs) produced higher WF (4.43 L/m2.h), %Wrecovery (30%) and RSF (60%) in comparison with multi-component draw solution (MCDS) with WF, %Wrecovery and RSF of 2.57 L/m2.h, 17% and 46%, respectively. DS with higher concentration produced the highest SWF and %Wrecovery and consumed less energy. MCDS with concentration of 200 g/L showed SWF in the range of 14.0 to 10.4 L/m2h and energy consumption of 0.312 kW/h m3 in comparison with 10 to 7.8 L/m2h and 0.23 kW/h m3 for MCDS with concentration of 100  g/L. Increasing the recirculation flow rate showed minimum effect on WF and up to 35% energy saving. Pure water extracted using liquid fertilizers utilizing the unique FO mass transport properties balanced nutrient requirement and the water quality parameters, thereby sustaining the aquaponics industry.

Synthesis and performance evaluation of nanostructured NaFe x Cr1-X (SO4)2 cathode materials in sodium ion batteries (SIBs).

This research work focuses on the synthesis and performance evaluation of NaFe x Cr1-X (SO4)2 (X = 0, 0.8 and 1.0) cathode materials in sodium ion batteries (SIBs). The novel materials having a primary particle size of around 100-200 nm were synthesized through a sol-gel process by reacting stoichiometric amounts of the precursor materials. The structural analysis confirms the formation of crystalline, phase pure materials that adopt a monoclinic crystal structure. Thermal analysis indicates the superior thermal stability of NaFe0.8Cr0.2(SO4)2 when compared to NaFe(SO4)2 and NaCr(SO4)2. Galvanostatic charge/discharge analysis indicates that the intercalation/de-intercalation of a sodium ion (Na+) into/from NaFe(SO4)2 ensues at about 3.2 V due to the Fe2+/Fe3+ active redox couple. Moreover, ex situ XRD analysis confirms that the insertion/de-insertion of sodium into/from the host structure during charging/discharging is accompanied by a reversible single-phase reaction rather than a biphasic reaction. A similar sodium intercalation/de-intercalation mechanism has been noticed in NaFe0.8Cr0.2(SO4)2which has not been reported earlier. The galvanostatic measurements and X-ray photoelectron spectroscopy (XPS) analysis confirm that the Cr2+/Cr3+ redox couple is inactive in NaFe x Cr1-X (SO4)2 (X = 0, 0.8) and thus does not contribute to capacity augmentation. However, suitable carbon coating may lead to activation of the Cr2+/Cr3+ redox couple in these inactive materials.