Polymer-Assisted Coprecipitation Synthesized Zinc Oxide Nanoparticles and Their Uses for Green Chemical Synthesis via Photocatalytic Glucose Conversions.

Biomass conversions to chemicals via various conventional technologies require high energy consumption, high temperature, high pressure, or high system cost. Alternatively, photocatalysis is one of the greener technologies because it utilizes the energy from lamps or natural sunlight with catalysts to synthesize chemicals under mild conditions and room temperature. In this work, zinc oxide (ZnO) particles were successfully synthesized using polyvinylpyrrolidone as an additive in coprecipitation to control the size and protect the aggregation. The crystal structure of hexagonal wurtzite was found in the obtained nanoparticles. The photocatalytic activities of the obtained samples were evaluated for the production of high-value chemicals (gluconic acid, xylitol, arabinose, and formic acid) via the photocatalytic conversion of glucose under UV-A irradiation. The photocatalytic results indicated the relationship of defects (i.e., oxygen vacancies and zinc vacancies) with glucose conversions. From the ZnO nanoparticles calcined at various temperatures from 400 to 700 °C, the one calcined at 700 °C showed the highest glucose conversion of 21.5% with a high yield of carboxylic acid products (gluconic acid and formic acid). The gluconic acid showed the highest yield of 15% for 180 min, while the formic acid, arabinose, and xylitol presented the highest yields of 7, 1, and 0.5% for 180 min, respectively. Pure ZnO nanoparticles can convert glucose into value-added products without adding an acid or base in the reaction.

Fiberglass cloth coated by coffee ground waste-derived carbon quantum dots/titanium dioxide composite for removal of caffeine and other pharmaceuticals from water.

Coffee ground waste from the coffee beverage preparation is mainly discarded and consequently ends up in landfill, which cause the contamination of caffeine in various environmental compartments. This study focuses on the upcycling of coffee-ground waste to carbon quantum dots (CQDs) for use as a modifying material to improve the visible light activity of titanium dioxide (TiO2). The CQD solution was synthesized by hydrothermal method, which has an average size of 2.80 ± 0.63 nm. The CQDs/TiO2 photocatalysts were prepared by combining CQD solutions at various amounts with sol-gel TiO2 and then coated on the fiberglass cloths (FGCs). The photocatalytic application mainly focuses on the removal of caffeine from the water. The photocatalytic experiment was preliminary run in a simple batch reactor under visible light. The 5CQDs/TiO2 coated FGC (5 mL of CQD solution/g of Ti-based on sol-gel) showed the best performance, and it was selected for the removal of caffeine and other pharmaceuticals (i.e., carbamazepine and ibuprofen) in the recirculating reactor. The removals of caffeine, carbamazepine, and ibuprofen after irradiation for 9 h were 82%, 88%, and 84%, respectively. The residual concentrations were significantly lower than the reported toxicity levels based on specific species. The changes in total organic carbon were observed, indicating the mineralization of pharmaceuticals in water. The 5CQDs/TiO2 coated FGC showed good flexible performance. No obvious loss of activity was observed for five runs. The actual wastewater from the coffee pot cleaning process was also tested. The removal was 80% for caffeine and 86% for color in the unit of the American Dye Manufacturers Institute (ADMI).

A facile route to synthesize n-SnO2/p-CuFe2O4 to rapidly degrade toxic methylene blue dye under natural sunlight.

In the present study, the n-SnO2/p-CuFe2O4 (p-CFO) complex was prepared by a two-step process. p-CFO synthesized by the molten salt method was coated with SnO2 synthesized by a facile in situ chemical precipitation method. The formation of n-SnO2/p-CFO was confirmed by powder X-ray diffraction (PXRD). Scanning electron microscopy (SEM) images showed that the sharp edges of uncoated pyramid-like p-CFO particles were covered by a thick layer of n-SnO2 on coated p-CFO particles. The complete absence of Cu and only 3 wt% Fe on the surface of the n-p complex observed in the elemental analysis using energy-dispersive X-ray spectroscopy (EDX) on the n-p complex confirmed the presence of a thick layer of SnO2 on the p-CFO surface. Diffuse reflectance spectroscopy (DRS) was employed to elucidate the bandgap engineering. The n-SnO2/p-CFO complex and p-CFO showed 87% and 58.7% methylene blue (MB) degradation in 120 min under sunlight, respectively. The efficiency of the n-p complex recovered after 5 cycles (73.5%) and was found to be higher than that of the uncoated p-CFO (58.7%). The magnetically separable property of the n-p complex was evaluated by using vibration sample magnetometry (VSM) measurements and it was confirmed that the prepared photocatalyst can be easily recovered using an external magnet. The study reveals that the prepared complex could be a potential candidate for efficient photodegradation of organic dyes under sunlight due to its efficient recovery and reusability owing to its magnetic properties.

Assessing mangrove species diversity, zonation and functional indicators in response to natural, regenerated, and rehabilitated succession.

The United Nations Decade on Ecosystem restoration (2021¬-2030) lists mangrove ecosystems as a restoration priority. Interest in their conservation has increased recently due to their widespread degradation. Anthropogenic stressors and rehabilitation practices, specifically, have resulted in a significant decline in their species compositions. We investigated the knowledge gaps in terms of potential spatial diversity, intertidal zonation, and the historic state of mangrove forest species, and tested the role of environmental factors such as topography, as well as rehabilitation practices on diversity. Diversity and complexity indices, surface elevation, and species and structural diversities along three simplified transect lines over a broad geographical area and under various management practices were analyzed in Trat province, Thailand. Quantitative statistical zonation analyses within each transect and at the landscape-scale were performed using randomization tests and hierarchical cluster analysis. A modified "automatic regrowth monitoring algorithm (ARMA)," based on Landsat (1987-2020) and Sentinel-2 MSI (2015-2020) annual median composites was also used. Fifteen species were identified, with Ceriops tagal as the dominant species. Statistical analysis, however, failed to identify any significant zonation patterns at transect or landscape-scales at specific elevations. Rehabilitated and naturally regenerated stands showed gradual increases in their Normalized Difference Infrared Index over time. After 30 years, the rehabilitated stands made up of Rhizophoraceae monocultures were the same height as the adjacent natural stands. Depending on the location and propagule availability, the diversity and structure of regenerated stands exhibited high variation. Effluent from shrimp farms may have contributed to the disturbance of the forest stands and changes in shrimp farming practices could have facilitated their recovery. The results of the present study provide a valuable diversity baseline for the study site and secondary succession in rehabilitated and regenerated mangroves. The ARMA algorithm has also been confirmed as a valuable tool for future investigations of secondary succession and mangrove biodiversity status.

Development of phosphorus recovery reactor for enlargement of struvite crystals using seawater as the magnesium source.

Struvite crystallization is an interesting method for the recovery of phosphorus (P) from wastewater. However, the struvite crystals obtained are small, which makes them difficult to separate from wastewater. A continuous reactor for enlarging struvite crystals was developed. Batch-scale experiments were conducted to investigate the optimum factors for the enlargement of struvite crystals. The results of pH experiments showed that P recovery efficiency increased with an increase of pH values (7.6 to 10), while the size of struvite crystals decreased. The results of the Mg:P ratios found that the maximum P recovery efficiency occurred at the maximum ratio of Mg:P. The sizes of struvite crystals were not significantly different. For the variation of temperature values, the results showed that P recovery efficiency and crystal sizes decreased when temperature values increased. Therefore, the optimized conditions for P recovery efficiency and enlargement of struvite crystals for the continuous reactor were pH 8.5 and an Mg:P ratio of 1.2:1 at 30 °C (room temperature). The treated swine wastewater and seawater were continuously fed in at the bottom of the reactor. After 30 days, the size of struvite crystals had increased from 125 µm to 0.83 mm (seven times).

Effect of magnesium dose on amount of pharmaceuticals in struvite recovered from urine.

Phosphorus (P) recovery was carried out through struvite precipitation from urines. Human urine, however, contains not only high nutrients for plants, such as P and nitrogen, but also pharmaceuticals and hormones. In this work, effects of magnesium (Mg) dose (in terms of Mg:P ratio) on P recovery efficiency and pharmaceutical amounts contained in struvite were investigated. Batch-scale experiments of synthetic and human urines revealed that struvite precipitation formed more X-shaped crystals with an increased molar ratio of Mg:P, while the amount of pharmaceuticals (tetracycline, demeclocycline, and oxytetracycline) in struvite decreased with an increased molar ratio of Mg:P. The lowest pharmaceutical amounts in struvite were found at the Mg:P ratio of 2:1 from both samples. Moreover, the maximum P recovery efficiency, quantity and purity of struvite were found in the range of 1.21 to 2:1. It indicated that the molar ratio of Mg:P has a significant impact on struvite precipitation in terms of pharmaceutical amounts in struvite; morphology, quantity and purity of struvite; and P recovery.

Phosphorus recovery: minimization of amount of pharmaceuticals and improvement of purity in struvite recovered from hydrolysed urine.

Struvite (MgNH4PO4·6H2O) is normally used as a fertilizer in agriculture, where struvite crystallization from hydrolysed human urine is a simple and reliable method for phosphorus (P) recovery. Human urine, however, contains high amount of pharmaceuticals, which may cause health risk for applications. This research investigates the possibility of decreasing the amount of pharmaceuticals (tetracycline, demeclocycline and oxytetracycline) in struvite crystals recovered from synthetic and human urines by focusing on storage time, and of increasing the quality of struvite production. Urines were stored for different times up to 15 days prior to recovery of phosphorus by two steps, spontaneous precipitation and struvite crystallization. The morphology of spontaneous precipitates and struvite crystals was observed. Spontaneous precipitation removed around 17-24% of phosphate from synthetic and human urines, while pharmaceuticals were removed with a quite high amount at a short storage time (5 days) and this amount decreased with increasing the storage time (10 and 15 days). Urines with>70% remaining phosphates were re-used for struvite crystallization by adding extra magnesium. It was found that maximum P-recovery efficiency could be achieved from struvite crystallization at 5-day storage time, 70% and 68% of remaining P in the separated supernatant from synthetic and human urines, respectively, whereas less than 1% pharmaceuticals remained in the struvite crystals from both samples. This indicates that the procedure in this work is a good method for phosphorus recovery, in which high struvite purity (>99%) is obtained with low amount of pharmaceuticals.

Phosphorus recovery from human urine and anaerobically treated wastewater through pH adjustment and chemical precipitation.

Increased population growth and food prices have resulted in more demand for fertilizers, especially phosphorus (P), to be used in agriculture and production of food crops. This research investigated the feasibility of P recovery from selected wastewaters in the form of precipitates only with pH adjustment. Human urine and effluent of an anaerobic digester treating a piggery's wastewater were employed to determine appropriate pH conditions for P recovery including solubility of the precipitates in an agricultural soil. From the laboratory experiments, the highest P recovery was found to be 106 mg per one litre of urine at pH 11. Due to its lower P content, the highest P recovery from one litre of the anaerobic digester effluent was 39 mg at pH 9. The X-ray diffraction analysis of the precipitates identified them to consist of struvite, syn-NH4MgPO4 6H2O, and other precipitate compounds consisting of CaCO3, NaCl and Mg3Al2(SiO4)3 and P contents of the precipitate samples were found to be 3-7%. When mixed with soils at a moisture content of 50%, the extents of P solubilized from the precipitate samples were in the range of 50-60%. Application of these experimental results to full-scale operation for P recovery is suggested.