Green synthesis of CaxLa1-xMnO3 with modulation of mesoporous and vacancies for efficient low concentration phosphate adsorption.

Phosphate concentrations in eutrophic surface waters are usually low, and efficient removal of low concentration phosphate remains a challenge. In this study, Ca-doped LaMnO3 synthesized at doping ratios, designated as CaxLa1-xMnO3 (x = 0, 0.2, 0.4, 0.7), were compared. It was found that, the adsorption capacity of Ca0.4La0.6MnO3 material reached 63.01 mg/g at pH = 5, increased by 63.6% over the undoped LaMnO3 perovskite. For long-term adsorption, Ca0.4La0.6MnO3 could constantly adsorb phosphate to avoid phosphate accumulation (<0.05 mg/L). This proves that Ca0.4La0.6MnO3 has the ability to control dynamic water eutrophication. Characterization and density functional theory results confirmed that CaxLa1-xMnO3 can increase the content of mesopores and oxygen vacancies, providing additional active sites. This reduces the adsorption energy of the La site, promotes electron transfer, and increases its affinity. It provides a new method for removing low-concentration phosphates.

Phosphate adsorption on LDHs-biochar composite: Double-layer model for quantifying the contribution of ion exchange and ligand exchange.

The adsorption performance of layered double hydroxides (LDHs) is limited owing to self-aggregation. To avoid this and effectively control the eutrophication of water bodies, biochar (BC) was synthesized, herein, by pyrolyzing waste sheep manure at 500°C, and Ca-Al-LDHs were loaded on the surface via a coprecipitation method to obtain Ca-Al-LDHs-BC(CA) composites with varying LDH contents. The fitted maximum adsorption capacities of the CA-5%, CA-10%, CA-15%, and CA-20% samples (corresponding to samples with 5%, 10%, 15%, and 20% LDHs, respectively) were 10.21, 16.14, 22.40, and 28.47 mg g-1, which were (when converted into metal proportions) 1.48, 1.23, 1.15, and 1.13 times of that of single hydrotalcite, respectively. The double-layer model was fitted using the Levenberg-Marquardt iterative algorithm, which when combined with the characterization results, confirmed that the adsorption of phosphate ions by CA-BC occurred via the double-layer adsorption mechanism. Two types of direct adsorption were observed: ion exchange, which resulted in first-layer adsorption, and ligand exchange, which resulted in second-layer adsorption, with first-layer adsorption accounting for a higher proportion. This double-layer adsorption mechanism showed that LDHs-BC could achieve higher ligand exchange performance compared to that achieved using only LDHs.

La-Ca/Fe-LDH-coupled electrochemical enhancement of organophosphorus removal in water: Organophosphorus oxidation improves removal efficiency.

Metal ions or metal (hydrogen) oxides are widely used as active sites in the construction of phosphate-adsorbing materials in water, but the removal of soluble organophosphorus from water remains technically difficult. Herein, synchronous organophosphorus oxidation and adsorption removal were achieved using electrochemically coupled metal-hydroxide nanomaterials. La-Ca/Fe-layered double hydroxide (LDH) composites prepared using the impregnation method removed both phytic acid (inositol hexaphosphate, IHP) and hydroxy ethylidene diphosphonic acid (HEDP) acid under an applied electric field. The solution properties and electrical parameters were optimized under the following conditions: organophosphorus solution pH = 7.0, organophosphorus concentration = 100 mg L-1, material dosage = 0.1 g, voltage = 15 V, and plate spacing = 0.3 cm. The electrochemically coupled LDH accelerates the removal of organophosphorus. The IHP and HEDP removal rates were 74.9% and 47%, respectively in only 20 min, 50% and 30% higher, respectively, than that of La-Ca/Fe-LDH alone. The removal rate in actual wastewater reached 98% in only 5 min. Meanwhile, the good magnetic properties of electrochemically coupled LDH allow easy separation. The LDH adsorbent was characterized using scanning electron microscopy with energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction analysis. It exhibits a stable structure under electric field conditions, and its adsorption mechanism mainly includes ion exchange, electrostatic attraction, and ligand exchange. This new approach for enhancing the adsorption capacity of LDH has broad application prospects in organophosphorus removal from water.

Spectral Measurements of Muzzle Flash with a Temporally and Spatially Modulated LWIR-Imaging Fourier Transform Spectrometer.

It is important to obtain information on an instantaneous target. A high-speed camera can capture a picture of an immediate scene, but spectral information about the object cannot be retrieved. Spectrographic analysis is a key tool for identifying chemicals. Detecting dangerous gas quickly can help ensure personal safety. In this paper, a temporally and spatially modulated long-wave infrared (LWIR)-imaging Fourier transform spectrometer was used to realize hyperspectral imaging. The spectral range was 700~1450 cm-1 (7~14.5 µm). The frame rate of infrared imaging was 200 Hz. The muzzle-flash area of guns with calibers of 5.56 mm, 7.62 mm, and 14.5 mm were detected. LWIR images of muzzle flash were obtained. Spectral information on muzzle flash was obtained using instantaneous interferograms. The main peak of the spectrum of the muzzle flash appeared at 970 cm-1 (10.31 µm). Two secondary peaks near 930 cm-1 (10.75 µm) and 1030 cm-1 (9.71 µm) were observed. Radiance and brightness temperature were also measured. The spatiotemporal modulation of the LWIR-imaging Fourier transform spectrometer provides a new method for rapid spectral detection. The high-speed identification of hazardous gas leakage can ensure personal safety.

B-site metal modulation of phosphate adsorption properties and mechanism of LaBO3 (B = Fe, Al and Mn) perovskites.

La-based adsorbents are widely used for controlling phosphate concentration in water bodies. In order to explore the effect of different B-site metals regulating La-based perovskites on phosphate adsorption, three La-based perovskites (LaBO3, B = Fe, Al, and Mn) were prepared using the citric acid sol-gel method. Adsorption experiments showed that LaFeO3 exhibited the highest adsorption capacity for phosphate, which was 2.7 and 5 times higher than those of LaAlO3 and LaMnO3, respectively. The characterization results demonstrated that LaFeO3 has dispersed particles exhibiting larger pore size and more pores than LaAlO3 and LaMnO3. Spectroscopy analysis and density functional theory calculation results showed that different B-positions cause a change in the type of perovskite crystals. Among them, the differences between lattice oxygen consumption ratio, zeta potential and adsorption energy are the main reasons for the differences in adsorption capacity. In addition, the adsorption of phosphate by La-based perovskites were well fitted with Langmuir isotherm and pursues the pseudo-second-order kinetic models. The maximum adsorption capacities were 33.51, 12.31 and 6.61 mg/g for LaFeO3, LaAlO3 and LaMnO3, respectively. The adsorption mechanism was mainly based on inner-sphere complexation and electrostatic attraction. This study provides an explanation for the influence of different B sites on phosphate adsorption by perovskite.

Adsorption properties and mechanism research of phosphorus with different molecular structures from aqueous solutions by La-modified biochar.

In order to explore the adsorption characteristics of phosphorus from molecules with different molecular structures and varying number of phosphate groups on metal-modified biochar, walnut shell biochar was modified with LaCl3 to prepare lanthanum-loaded biochar (BC-La). Adsorption of four polar components, namely phytic acid (IHP), adenosine-5'-disodium triphosphate (5-ATP), hydroxyethylidene diphosphonic acid (HEDP), and sodium pyrophosphate (PP), was studied. The adsorption properties and mechanism of phosphorus sorption by BC-La were analyzed by SEM-EDS and FTIR for the different structures. The results showed that the maximum adsorption capacity of BC-La for IHP, 5-ATP, HEDP, and PP was 85.85, 9.04, 15.80, and 14.45 mg/g, respectively. The adsorption capacity was positively correlated with the polarity of organic phosphorus. The adsorption behavior conformed to the quasi second-order kinetic fitting equation, and the increase of temperature was conducive to the removal of all four phosphorus pollutants. BC-La adsorbs IHP and HEDP mainly through electrostatic attraction. The adsorption of 5-ATP and PP is dominated by complexation. The La-modified biochar has broad prospects in water remediation, which can provide a theoretical basis for removal of different forms of phosphorus pollutants and prevention and control of water eutrophication.

CO Detection System Based on TDLAS Using a 4.625 µm Interband Cascaded Laser.

During industrial operations and in confined places, carbon monoxide (CO) may collect in harmful proportions if ventilation is insufficient or appliances are not properly maintained. When the concentration of CO is too high, it might result in suffocation, coma, or even death. The detection of tiny concentrations of CO plays an important role in safe production. Due to the selective absorption of specific wavelengths of light by gas molecules, lasers have a wide range of applications in the field of gas detection. In this paper, a tunable diode laser absorption spectroscopy (TDLAS) system for CO detection was constructed using an interband cascaded laser (ICL) with a central wavelength of 4.625 µm. The modulated signal generated by the FPGA module was output to the laser controller to modulate the laser. The signal received by the detector was input to the FPGA module. After lock-in amplification, the second harmonic signal of high frequency modulation was output. Several concentrations of CO that were dispersed via static gas distribution were identified. A CO detection system with an open optical path was constructed, and the detection distance was about 8 m. The minimum detectable concentration is around 10.32 ppmm. The concentration of CO in the open optical path was 510.6 ppmm, according to the calibration of the detected concentration. The remote detection system based on TDLAS using an ICL can be used to monitor CO in the open optical path.

Oyster Shell Modified Tobacco Straw Biochar: Efficient Phosphate Adsorption at Wide Range of pH Values.

In order to improve the phosphate adsorption capacity of Ca-loaded biochar at a wide range of pH values, Ca (oyster shell) was loaded as Ca(OH)2 on the tobacco stalk biochar (Ca-BC), which was prepared by high-temperature calcination, ultrasonic treatment, and stirring impregnation method. The phosphorus removal performance of Ca-BC adsorption was studied by batch adsorption experiments, and the mechanism of Ca-BC adsorption and phosphorus removal was investigated by SEM-EDS, FTIR, and XRD. The results showed that after high-temperature calcination, oyster shells became CaO, then converted into Ca(OH)2 in the process of stirring impregnation and had activated the pore expansion effect of biochar. According to the Langmuir model, the adsorption capacity of Ca-BC for phosphate was 88.64 mg P/g, and the adsorption process followed pseudo-second-order kinetics. The Ca(OH)2 on the surface of biochar under the initial pH acidic condition preferentially neutralizes with H+ acid-base in solution, so that Ca-BC chemically precipitates with phosphate under alkaline conditions, which increases the adsorption capacity by 3-15 times compared with other Ca-loaded biochar. Ca-BC phosphate removal rate of livestock wastewater (pig and cattle farms) is 91~95%, whereas pond and domestic wastewater can be quantitatively removed. This study provides an experimental basis for efficient phosphorus removal by Ca-modified biochar and suggesting possible applications in real wastewater.

Modified biochar improves the storage capacity and adsorption affinity of organic phosphorus in soil.

The loss of soil organic phosphorus can easily cause water eutrophication. In order to effectively reduce the loss of soil organic phosphorus, this manuscript investigated the adsorption of soil organic phosphorus by lanthanum modified biochar (BC), traditional adsorbent gypsum (GY) and zeolite (ZE) by taking phytic acid as the representative. The adsorption isotherm model and kinetic models were used to fit the phosphorus absorption characteristics of the adsorbents. The effects of initial pH and temperature on the adsorption capacity were discussed, and the adsorption mechanism of each adsorbent was explained by means of FTIR and XRD. The results showed that the adsorption capacity of phytate phosphorus followed the trend of BCTS > GYTS > ZETS > TS (soil), and the maximum phosphorus adsorption capacity obtained from Langmuir isotherm for treatment with BCTS was 2.836 mg g-1, and the treatment had the strongest affinity for phytate phosphorus and also the ability to store phosphorus. The adsorption process fits well with Langmuir isotherm equation and pseudo-second-order kinetic equation, and the adsorption behavior of phytate phosphorus was mainly controlled by the chemisorption of monolayer. When the concentration of phytate phosphorus was 100 mg L-1, percentage of modified biochar added to the soil was 3% and the pH was 6, the adsorption capacity reached the maximum, and the maximum adsorption capacity was 2.000 mg g-1. The results of FTIR and XRD characterization showed that complexation was the main adsorption mechanism. In this study, the combination of modified biochar and soil phytate phosphorus can provide a good theoretical basis for reducing the loss of soil organic phosphorus.