Phosphorus recovery from wastewater and sludge

Wastewater and sludge are potential resource of phosphorus (P) for fertilizer production. One method of recovering phosphorus is via chemical precipitation. In the study, phosphorus was recovered from wastewater and sludge. First, hydrolysis was carried out to release the phosphorus in the sludge by the addition of 1.0M acid (sulfuric acid) or base (sodium hydroxide) solution mixed for three hours at 200 rpm. The hydrolyzed sludge was filtered, and the pH of the solution was adjusted to 9.0. Precipitation for both wastewater and hydrolyzed sludge solution was carried out using magnesium chloride hexahydrate (MgCl2•6H2O) and ammonium chloride (NH4Cl). The mixture was stirred for an hour for crystallization. Precipitates were allowed to settle for 24 hours before it was filtered and dried in an oven at 55-58oC for 24 hours. The dried sample was grinded and characterized using Fourier transform infrared spectroscopy (FTIR), x-ray fluorenscence (XRF), and scanning electron microscope with energy-dispersive x-ray spectroscopy(SEM-EDX)

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Sustainable Desalination by 3:1 Reduced Graphene Oxide/Titanium Dioxide Nanotubes (rGO/TiONTs) Composite via Capacitive Deionization at Different Sodium Chloride Concentrations

The capability of novel 3:1 reduced graphene oxide/titanium dioxide nanotubes (rGO/TiONTs) composite to desalinate using capacitive deionization (CDI) employing highly concentrated NaCl solutions was tested in this study. Parameters such as material wettability, electrosorption capacity, charge efficiency, energy consumption, and charge-discharge retention were tested at different NaCl initial concentrations—100 ppm, 2000 ppm, 15,000 ppm, and 30,000 ppm. The rGO/TiONTs composite showed good material wettability before and after CDI runs with its contact angles equal to 52.11° and 56.07°, respectively. Its two-hour electrosorption capacity during CDI at 30,000 ppm NaCl influent increased 1.34-fold compared to 100 ppm initial NaCl influent with energy consumption constant at 1.11 kWh per kg with NaCl removed. However, the percentage discharge (concentration-independent) at zero-voltage ranged from 4.9–7.27% only after 30 min of desorption. Repeated charge/discharge at different amperes showed that the slowest charging rate of 0.1 A·g−1 had the highest charging time retention at 60% after 100 cycles. Increased concentration likewise increases charging time retention. With this consistent performance of a CDI system utilizing rGO/TiONTs composite, even at 30,000 ppm and 100 cycles, it can be a sustainable alternative desalination technology, especially if a low charging current with reverse voltage discharge is set for a longer operation

Evaluation of bacterial cellulose-sodium alginate forward osmosis membrane for water recovery

Water resources are very important to sustain life. However, these resources have been subjected to stress due to population growth, economic and industrial growth, pollution and climate change. With these, the recovery of water from sources such as wastewater, dirty water, floodwater and seawater is a sustainable alternative. The potential of recovering water from these sources could be done by utilizing forward osmosis, a membrane process that exploits the natural osmotic pressure gradient between solutions which requires low energy operation. This study evaluated the potential of forward osmosis (FO) composite membranes fabricated from bacterial cellulose (BC) and modified with sodium alginate. The membranes were evaluated for water flux and salt rejection. The effect of alginate concentrations and impregnation temperatures were evaluated using 0.6 M sodium chloride solution as feed and 2 M glucose solution as the draw solution. The membranes were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), and Contact Angle Meter (CAM). The use of sodium alginate in BC membrane showed a thicker membrane (38.3 μm to 67.6 μm), denser structure (shown in the SEM images), and more hydrophilic (contact angle ranges from 28.39° to 32.97°) compared to the pristine BC membrane (thickness = 12.8 μm and contact angle = 66.13°). Furthermore, the alginate modification lowered the water flux of the BC membrane from 9.283 L/m2-h (LMH) to value ranging from 2.314 to 4.797 LMH but the improvement in salt rejection was prominent (up to 98.57%). © 2018 Penerbit UTM Press. All rights reserved

Sustainable desalination by 3:1 reduced graphene oxide/titanium dioxide nanotubes (rGO/TiONTs) composite via capacitive deionization at different sodium chloride concentrations

The capability of novel 3:1 reduced graphene oxide/titanium dioxide nanotubes (rGO/TiONTs) composite to desalinate using capacitive deionization (CDI) employing highly concentrated NaCl solutions was tested in this study. Parameters such as material wettability, electrosorption capacity, charge efficiency, energy consumption, and charge-discharge retention were tested at different NaCl initial concentrations—100 ppm, 2000 ppm, 15,000 ppm, and 30,000 ppm. The rGO/TiONTs composite showed good material wettability before and after CDI runs with its contact angles equal to 52.11° and 56.07°, respectively. Its two-hour electrosorption capacity during CDI at 30,000 ppm NaCl influent increased 1.34-fold compared to 100 ppm initial NaCl influent with energy consumption constant at 1.11 kWh per kg with NaCl removed. However, the percentage discharge (concentration-independent) at zero-voltage ranged from 4.9–7.27% only after 30 min of desorption. Repeated charge/discharge at different amperes showed that the slowest charging rate of 0.1 A·g−1 had the highest charging time retention at 60% after 100 cycles. Increased concentration likewise increases charging time retention. With this consistent performance of a CDI system utilizing rGO/TiONTs composite, even at 30,000 ppm and 100 cycles, it can be a sustainable alternative desalination technology, especially if a low charging current with reverse voltage discharge is set for a longer operation. © 2019 by the authors. Licensee MDPI, Basel, Switzerland

Determination of the carbon dioxide sequestration potential of a nickel mine mixed dump through leaching tests

Carbon dioxide sequestration via mineralization is one of the methods that has the capability to efficiently store carbon dioxide in a stable form. A mixed dump sample collected from a nickel laterite mine in Southern Philippines was tested for its carbon dioxide sequestration potential through HCl leaching tests, employing the Face-Centered Cube (FCC) experimental design for Response Surface Methodology (RSM). Mineralogical analysis performed through X-ray diffraction (XRD) analysis suggests the presence of three minerals, namely goethite, khademite and lizardite; additional X-ray fluorescence (XRF) and inductively-coupled plasma optical emission spectroscopy (ICP-OES) results, however, established goethite as the main component due to the dominance of iron in the sample. Morphological analyses performed through a scanning electron microscope (SEM) and the Brunauer–Emmett–Teller (BET) method suggest high accessible surface area despite considerable variability in sample composition. Leaching tests further confirmed the high reactivity of the mixed dump as high extraction rates were obtained for iron, with the maximum iron extraction efficiency of 95.37% reported at 100 ◦C, 2.5 M, and 2.5 h. The carbon dioxide sequestration potential of the mixed dump was reported as the amount of CO2 that can be sequestered per amount of sample, which was calculated to be 327.2 mg CO2/g sample using the maximum iron extraction obtained experimentally. © 2019 by the authors

Evaluation of the leaching characteristics of low-grade nickel laterite waste rock for indirect carbon sequestration application

The potential utilization of waste rock obtained from an active nickel mine site in Mindanao, the Philippines for indirect carbon sequestration is explored in this study. X-ray diffraction (XRD), X-ray fluorescence (XRF), and inductively coupled plasma optical emission spectroscopy (ICP-OES) results showed that the sample is rich in iron, existing in three different forms: goethite (α-FeOOH), chromite (FeCr2O4), and magnetite (Fe3O4). Leaching tests performed using hydrochloric acid (HCl) showed high iron extraction rates, with a maximum average extraction efficiency of 95.35% obtained at 100°C, 4 M HCl, and 1.0 h. Morphological and physicochemical analyses conducted through scanning electron microscopy and Brunauer–Emmett–Teller (BET) method supported the high extraction rates obtained for Fe, which is due to the higher reactivity of the sample to the leaching agent as well as the higher availability of accessible sites for reaction on the sample surface as compared to other mine wastes that are previously utilized. The nickel laterite waste rock sample has the potential to be used as a feedstock for iron carbonation in indirect carbon sequestration; however, challenges such as the use of sulfide source and cost requirements must be addressed in order to fully determine its viability for industrial scale application. © 2020 The Korean Society of Mineral and Energy Resources Engineers (KSMER)

Synthesis of reduced graphene oxide/titanium dioxide nanotubes (rGO/TNT) composites as an electrical double layer capacitor

© 2018 by the authors. Composites of synthesized reduced graphene oxide (rGO) and titanium dioxide nanotubes (TNTs) were examined and combined at different mass proportions (3:1, 1:1, and 1:3) to develop an electrochemical double layer capacitor (EDLC) nanocomposite. Three different combination methods of synthesis—(1) TNT introduction during GO reduction, (2) rGO introduction during TNT formation, and (3) TNT introduction in rGO sheets using a microwave reactor—were used to produce nanocomposites. Among the three methods, method 3 yielded an EDLC nanomaterial with a highly rectangular cyclic voltammogram and steep electrochemical impedance spectroscopy plot. The specific capacitance for method 3 nanocomposites ranged from 47.26–165.22 F/g while that for methods 1 and 2 nanocomposites only ranged from 14.03–73.62 F/g and 41.93–84.36 F/g, respectively. Furthermore, in all combinations used, the 3:1 graphene/titanium dioxide-based samples consistently yielded the highest specific capacitance. The highest among these nanocomposites is 3:1 rGO/TNT. Characterization of this highly capacitive 3:1 rGO/TNT EDLC composite revealed the dominant presence of partially amorphous rGO as seen in its XRD and SEM with branching crystalline anatase TNTs as seen in its XRD and TEM. Such property showed great potential that is desirable for applications to capacitive deionization and energy storage

Fabrication of forward osmosis membrane using nata-de-coco as raw materials for desalination

© 2020. A Forward Osmosis (FO) membrane was fabricated using a locally available material nata de coco (NDC) to form a bacterial cellulose (BC) film. Sodium alginate was used to form composites with the BC film. Two concentrations (10% and 15%) of cross-linking agent, CaCl2, were compared in terms of its performance as a FO membrane for application in desalination. Two salts were compared as draw solution: 2M sucrose (C12H22O11) and 2M magnesium chloride (MgCl2). The performance of the fabricated NDC-FO membrane was investigated in terms of water flux, salt flux and percent salt rejection in a laboratory-scale FO system. The 15% CaCl2 solution was observed to give high water flux, low salt flux, and high salt rejection compared to the 10% CaCl2. The 15% CaCl2 solution produced a more tensile membrane compared to 10% CaCl2, one endures pressure at the suction points of the FO module while the other breaks after some time of operation, respectively. The NDC-FO membrane has an average contact angle of 14.137° with an average thickness of 0.159 mm. The 2M MgCl2 performs better than sucrose as a draw solution. The commercial Cellulose Tri-Acetate (CTA) FO membrane was used to benchmark the performance of NDC-FO membrane. The NDC-FO membrane produces a water flux of 4.01 LMH with 88.39% salt rejection, which is comparable to the water flux of CTA with 7.97 LMH and 100% salt rejection. Results showed the potential of nata de coco as raw material for FO membrane

Phosphorus recovery from wastewater and sludge

Wastewater and sludge are potential resource of phosphorus (P) for fertilizer production. One method of recovering phosphorus is via chemical precipitation. In the study, phosphorus was recovered from wastewater and sludge. First, hydrolysis was carried out to release the phosphorus in the sludge by the addition of 1.0M acid (sulfuric acid) or base (sodium hydroxide) solution mixed for three hours at 200 rpm. The hydrolyzed sludge was filtered, and the pH of the solution was adjusted to 9.0. Precipitation for both wastewater and hydrolyzed sludge solution was carried out using magnesium chloride hexahydrate (MgCl2•6H2O) and ammonium chloride (NH4Cl). The mixture was stirred for an hour for crystallization. Precipitates were allowed to settle for 24 hours before it was filtered and dried in an oven at 55-58oC for 24 hours. The dried sample was grinded and characterized using Fourier transform infrared spectroscopy (FTIR), x-ray fluorenscence (XRF), and scanning electron microscope with energy-dispersive x-ray spectroscopy(SEM-EDX)