Developing persulfate-activator soft solid (PASS) as slow release oxidant to remediate phenol-contaminated groundwater

The research objective was to develop a persulfate-activator soft solid (PASS) as a biodegradable slow-release oxidant to treat phenol-contaminated groundwater. PASS was prepared by graft copolymerization of acrylic acid (AA) and acrylamide (AM) onto 1% (w/v) sodium alginate mixed with 500 mg L−1 sodium persulfate and 5 mg L−1 ferrous sulfate. The physical and chemical properties of PASS were characterized using scanning electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, the water content and swelling ratio. Various variables, including the ratio of AA/AM, pH, temperature and the type of groundwater cations affecting PS release, were investigated. The maximum PS release in DI water was 98% in the ratio of PASS 1 (AA/AM, 75/25), 96% at pH 3, 83% at 25 °C, and 80% with Na+. The major factors controlling PS release were the AA/AM ratio and pH. PASS 1 can be stable in size and shape for 6–8 days and completely degraded within 34 days. The degradation rates of 10 mgL−1 phenol using PASS produced the highest kobs values for each variable at a ratio of PASS 1 (k = 0.1408 h−1), pH 7 (k = 0.1338 h−1), 25 °C (k = 0.1939 h−1), and Ca2+ (k = 0.1336 h−1). The temperature of the groundwater was key to driving the reaction between PS and phenol. PASS 1 was applied in simulated phenol-contaminated groundwater via horizontal tanks containing Ottawa sand. The results indicated 93.2% phenol removal within 72 h in a narrow horizontal flow tank and 41.7% phenol removal in a wide horizontal flow tank with aeration

Remediating chloroacetanilide -contaminated water using zerovalent iron

Pesticide spills and discharges can result in ground and surface water contamination. Simple iron treatment provides an effective and inexpensive remediation tool for soil and water contaminated with chloroacetanilide herbicides. We found the effectiveness of zerovalent iron (Fe0) to dechlorinate aqueous metolachlor (2-chloro-N-(2-ethyl-6-methyl phenyl)- N-(2-methoxy-1-methyl ethyl) acetamide) was greatly enhanced in the presence of Al, Fe(II) or Fe(III) salts, with the following order of destruction kinetics observed: Al2(SO4)3 \u3e AlCl 3 \u3e Fe2(SO4)3 \u3e FeCl3. A common observation was the formation of green rusts, mixed Fe(II)/Fe(III) hydroxides with interlayer anions that impart a greenish-blue color. The mechanism responsible for enhanced metolachlor loss may be related to the role these salts play in facilitating Fe(II) release. To investigate this catalytic effect, we characterized changes in Fe0 composition during the treatment of metolachlor. Raman microscopic analysis and X-ray diffraction indicated that the iron source was initially coated with a thin layer of magnetite (Fe3O4), maghemite (γ-Fe 2O3), and wüstite (FeO). Temporal mineralogical analysis indicated akaganeite (β-FeOOH), goethite (α-FeOOH), magnetite, and lepidocrocite (γ-FeOOH) formed in the Fe0-metolachlor suspension when Al2(SO4)3 or FeSO4 were present. Green rust II (Fe6(OH)12SO4) was also transiently identified in Fe0 treatments containing FeSO4. Although conditions favoring green rust formation in a Fe 0-batch system increased metolachlor dechlorination, we determined that green rust itself can only marginally contribute to transforming metolachlor. In contrast, metolachlor dechlorination was observed in a batch system containing magnetite or goethite and FeSO4 at pH 8. These results indicate that creating conditions favoring green rust facilitate Fe0-mediated dechlorination of metolachlor by providing an available source of Fe(II)/Fe(III) and generating iron oxide surfaces that can coordinate Fe(II). This information can be useful in designing and managing Fe0-treatment systems

Advancing Cassava Age Estimation in Precision Agriculture: Strategic Application of the BRAH Algorithm

Cassava crop age estimation is crucial for optimizing irrigation, fertilization, and pest management, which are key components of precision agriculture. Accurate knowledge of crop age allows for effective resource application, minimizing environmental impact and enhancing yield predictions. The Bare Land Referenced Algorithm from Hyper-Temporal Data (BRAH) is used for bare land classification and cassava crop age estimation, but it traditionally requires manual NDVI thresholding, which is challenging with large datasets. To address this limitation, we propose automating the thresholding process using Otsu’s method and enhancing the image contrast with histogram equalization. This study applies these enhancements to the BRAH algorithm for bare land classification and cassava crop age estimation in Ratchaburi, Thailand, utilizing a dataset of 604 Landsat satellite images from 1987 to 2024. Our research demonstrates the accuracy and practicality of the BRAH algorithm, with Otsu’s method providing 94% accuracy in detecting the bare land validation locations with an average deviation of 8.78 days between the acquisition date and the validated date. This approach facilitates precise agricultural planning and management, promoting sustainable farming practices and supporting several Sustainable Development Goals (SDGs)

Transformation of Hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) by Permanganate

The chemical oxidant permanganate (MnO4−) has been shown to effectively transform hexa-hydro-1,3,5-trinitro-1,3,5-triazine (RDX) at both the laboratory and fieldscales. We treated RDX with MnO4− with the objective of quantifying the effects of pH and temperature on destruction kinetics and determining reaction rates. A nitrogen mass balance and the distribution of reaction products were used to provide insight into reaction mechanisms. Kinetic experiments (at pH ~7, 25 °C) verifiedthat RDX−MnO4− reaction was first-order with respect to MnO4− and initial RDX concentration (second-order rate: 4.2 × 10−5 M−1 s−1). Batch experiments showed that choice of quenching agents (MnSO4, MnCO3, and H2O2) influenced sample pH and product distribution. When MnCO3 was used as a quenching agent, the pH of the RDX−MnO4− solution was relatively unchanged and N2O and NO3− constituted 94% of the N-containing products after 80% of the RDX was transformed. On the basis of the preponderance of N2O produced under neutral pH (molar ratio N2O/NO3 ~5:1), no strong pH effect on RDX−MnO4− reaction rates, a lower activation energy than the hydrolysis pathway, and previous literature on MnO4− oxidation of amines, we propose that RDX−MnO4− reaction involves direct oxidation of the methylene group (hydride abstraction), followed by hydrolysis of the resulting imides, and decarboxylation of the resulting carboxylic acids to form N2O, CO2, and H2O

Enhanced Photo-Fenton Activity Using Magnetic Cu\u3csub\u3e0.5\u3c/sub\u3eMn\u3csub\u3e0.5\u3c/sub\u3eFe\u3csub\u3e2\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e Nanoparticles as a Recoverable Catalyst for Degrading Organic Contaminants

Interest in using various nanoparticle catalysts to activate H2O2 with light for organic contaminant and wastewater treatment is steadily increasing. We successfully synthesized magnetically recoverable Cu0.5Mn0.5Fe2O4 nanoparticles using a simple co-precipitation method followed by melamine-assisted calcination. Material characterization revealed that melamine acted as a coordinating agent during the calcination process that promoted a ferrite structure. Copper (Cu)-substitution effectively decreased material aggregation and promoted catalytic activities. Cu0.5Mn0.5Fe2O4 nanoparticles showed outstanding catalytic performance on several organic contaminants (87.6–100.0% removal within 2 h). Using oxytetracycline (OTC) as a surrogate wastewater constituent, we found that the hydroxyl radical (•OH) and superoxide anions (•O2−) were the active radical species involved in OTC degradation. Cu0.5Mn0.5Fe2O4 nanoparticles exhibited excellent photo-Fenton catalytic ability in real wastewater and demonstrated high material stability, even after four consecutive uses (i.e., fourth cycle). In a pilot-scale experiment (10 L), we provide proof that our rigorous treatment system was able to remove remnant OTC, TOC, and also any available colloidal particles to only 1 NTU. Ecotoxicity studies using an aquatic plant (Hydrilla verticillata) and zooplankton revealed that treated water could be reused in various ratios. Furthermore, at 5% of treated water, rapid leaf recovery and a significant increase in rotifer numbers were reported. These observations support the use of Cu0.5Mn0.5Fe2O4/H2O2/light as an efficient and environmentally friendly catalytic system for treatment of organic contaminants, and a radical generating mechanism is proposed

Enhanced Photo-Fenton Activity Using Magnetic Cu_0.5Mn_0.5Fe₂O₄ Nanoparticles as a Recoverable Catalyst for Degrading Organic Contaminants

Interest in using various nanoparticle catalysts to activate H2O2 with light for organic contaminant and wastewater treatment is steadily increasing. We successfully synthesized magnetically recoverable Cu0.5Mn0.5Fe2O4 nanoparticles using a simple co-precipitation method followed by melamine-assisted calcination. Material characterization revealed that melamine acted as a coordinating agent during the calcination process that promoted a ferrite structure. Copper (Cu)-substitution effectively decreased material aggregation and promoted catalytic activities. Cu0.5Mn0.5Fe2O4 nanoparticles showed outstanding catalytic performance on several organic contaminants (87.6–100.0% removal within 2 h). Using oxytetracycline (OTC) as a surrogate wastewater constituent, we found that the hydroxyl radical (•OH) and superoxide anions (•O2−) were the active radical species involved in OTC degradation. Cu0.5Mn0.5Fe2O4 nanoparticles exhibited excellent photo-Fenton catalytic ability in real wastewater and demonstrated high material stability, even after four consecutive uses (i.e., fourth cycle). In a pilot-scale experiment (10 L), we provide proof that our rigorous treatment system was able to remove remnant OTC, TOC, and also any available colloidal particles to only 1 NTU. Ecotoxicity studies using an aquatic plant (Hydrilla verticillata) and zooplankton revealed that treated water could be reused in various ratios. Furthermore, at 5% of treated water, rapid leaf recovery and a significant increase in rotifer numbers were reported. These observations support the use of Cu0.5Mn0.5Fe2O4/H2O2/light as an efficient and environmentally friendly catalytic system for treatment of organic contaminants, and a radical generating mechanism is proposed