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Activated carbon (AC) adsorption is commonly used for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) removal from flue gas. However, the AC available in the market predominantly possesses a substantial specific surface area and numerous micropores leading to significant variations in their adsorption characteristics. In this study, three types of activated carbon (AC) impregnated with different activating agents, namely K2CO3, KOH, and H3PO4 were evaluated for their effectiveness in removing PCDD/Fs and dl-PCBs compounds. For dl-PCBs, AC impregnated with H3PO4 resulted in a substantial reduction of PCB concentrations with an impressive 98% reduction achieved. Impregnation with KOH proved even more effective attaining a remarkable 99% reduction. In contrast, impregnation with K2CO3 while still effective achieved a slightly lower reduction rate of 95%. For PCDD/F, LACH3PO4 showed selectivity in achieving high reductions across both CDD and CDF congeners however proved effective in reducing the ∑PCCDF from 403.94 ng/Nm3 to 3.463 ng/Nm3 and ∑TEQ from 41.34 ng I-TEQ/Nm3 to 0.35 ng I-TEQ Nm3. LACKOH proved effective in reducing the ∑PCCDF from 540.45 ng/Nm3 to 0.25 ng/Nm3 and ∑TEQ from 57.42 ng I-TEQ/Nm3 to 0.12 ng I-TEQ Nm3 obtaining the overall removal efficiency of 99.5%. While the LACKOH injections were successful in the absorption of PCDD/Fs from the gas phase, it was observed that certain PCDD/F congeners became desorbed and entrapped within the ash necessitating further treatment of the ash residue. The ash underwent a thermal treatment first at 300 °C and 500 °C. The thermal treatment at 500 °C achieved a remarkable degradation of 99.7% removal efficiency rendering the ash and residue safe for disposal in a landfill site.Article Highlights: The study assessed K2CO3, KOH, and H3PO4 for AC activation efficiency. KOH proved most effective (99.5% removal). Post-ash treatment at 500 °C degraded PCDD/Fs by 99.7%, ensuring safe landfill disposal. [ABSTRACT FROM AUTHOR]

Comprehensive use of available biomass, especially low-cost forestry waste to produce bioenergy, materials have great meaning for realization of green and sustainable chemical processes. In this work, forestry sawdusty waste (SD) was used to produce biochar (SDBC-P) via a H3PO4 assisted hydrothermal carbonization method. And a novel zirconium-coordinated biochar catalyst Zr-SDBC-P has been prepared by self-assembly method. Characterization results revealed that hydrothermal carbonization in the presence of H3PO4 promoted the formation of oxygen-containing functional groups (–COOH, Ar–OH) which were used as ligand to obtain high contents of Lewis acid − base sites (Zr4+–O2−). Zr-SDBC-P-4 showed satisfactory catalytic activity in synthesis of bioderived γ-valerolactone (GVL) from ethyl levulinate (EL). EL conversion of 98.2% and GVL selectivity of 85.4% were obtained within 5 h at 170 °C. In addition, Zr-SDBC-P-4 displayed outstanding chemical stability. There was no obvious decrease of GVL yield after being used for six cycles. Overall, this work offered a viewpoint to design catalyst from value-added utilization of biomass waste. [ABSTRACT FROM AUTHOR]

In this study, using waste materials such as hard almond bark and palm kernels, the porous activated carbon has been synthesized by chemical activation method with activation agents of sodium hydroxide (NaOH), sodium chloride (NaCl), and phosphoric acid (H3PO4). Then, the structural, morphological, and optical properties of the synthesized activated carbons were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and UV–Vis spectroscopy. The XRD patterns showed that an activated carbon structure was formed in all the samples synthesized with chemical activators. The SEM and TEM images showed that there is no porosity and pitted for raw and primary carbon samples of hard almond bark and palm kernels, but for activated carbon by various activating agents, it was clearly porous structure in the activated samples. Also, in the FTIR spectra of activated carbon, it was confirmed that there are carbon single and double bonds for in all samples. The measurement of the optical absorption coefficient (α) and optical band gap (Eg) of porous carbon nanostructures showed that α is in order of 106–107 cm−1 and energy gap is in range of 1.98–2.83 eV. The activated carbon sample synthesized from almond bark with H3PO4 activator has highest energy gap (Eg = 2.83 eV) and NaCl activator has lowest energy gap (Eg = 1.98 eV). [ABSTRACT FROM AUTHOR]

In this study, activated carbon was synthesized using the almond shell and palm kernel by physical activation with water vapor and chemical activation with phosphoric acid (H3PO4) methods. Then, the structural and optical properties of the activated carbons were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and UV–Vis spectroscopy. The SEM images showed that in the raw sample of hard almond shell and palm kernel, there is no porosity and pores, but in the activated carbon samples, porosity and structural defects were clearly observed. The XRD patterns showed that porous and amorphous structure was formed in all samples synthesized with physical and chemical activation. The results of FTIR spectra of activated carbons showed that there are carbon functional groups in all samples. The optical absorption coefficient (α) of the activated carbon with physical and chemical activation methods was obtained in order of 105–106. The band gap measurement of porous nanostructures showed that the activated carbon synthesized with chemical and physical activation methods have energy gap (Eg) in region = 2.80 to 3.15 eV and urbach energy (EU) in region = 120 to 210 meV. [ABSTRACT FROM AUTHOR]

This research aims to ascertain the optimum conditions and interaction effects of selected variables via response surface methodology incorporated with central composite design in a batch treatment system. A quadratic model was obtained through the influence effects of the selected variables. Four variables pH (A), initial concentration (B), contact time (C), and biosorbent dosage (D), were selected to obtain high efficiency in the removal of the steroid hormone 17α-ethinylestradiol using modified kenaf core. The biosorbent characterisation, which was modified via chemical acid activation, was investigated through surface morphology structures using field emission scanning electron microscopy, Brunauer–Emmett–Teller, and fourier transform infrared spectroscopy analyses. The optimum conditions in an aqueous solution, obtained through a verification optimisation process, are 5.9, 28.2 mg/L, 216 min, and 0.40 g for variables A, B, C, and D, respectively. The pH and initial concentration explain the most significant interaction effect (F-value 23.12) at pH 4.6–5.8, with the lowest initial concentration being a good sign for the application of modified kenaf core in the real environment. The optimum removal rate computed in the quadratic model was 100%. In comparison, the real experimental set-up achieved a 99.3% 17α-ethinylestradiol removal rate, which is in great agreement with the predicted rate with a small percentage error (0.7%) between the experimental and predicted values. Linear regression provided a best-fit isotherm with the Langmuir model. The results prove that modified kenaf core has enormous potential for 17α-ethinylestradiol removal due to its excellent surface morphological structure and high removal efficiency. [ABSTRACT FROM AUTHOR]

Activated carbon was prepared from grape marc after activation with H3PO4. It was used to adsorb an azo dye (AO7) from aqueous solutions. The adsorption process was spontaneous (∆G ˂ 0) and endothermic as indicated by the thermodynamic parameters (∆H = 12.28 kJ /mol and ∆S = 0.041 kJ/mol K). The adsorption capacity was found to increase with increasing temperature (from 140.5 mg/g at 25 °C to 174.6 mg/g at 55 °C). The nonlinear regression adsorption equilibrium modeling revealed that the adsorption of AO7 by the activated carbon was best represented by the Freundlich model (R2 > 0.975). The desorption of the dye and the regeneration of the activated carbon are crucial steps to consider in evaluating the efficacy of contaminant elimination from aqueous solutions. Among six solvents used, ethanol had the greatest capacity of dye desorption from the activated carbon (48%). The FTIR investigation revealed that ethanol was partially bound to the activated carbon which adversely decreases the adsorption capacity in each adsorption–desorption cycle. The investigation carried out revealed that the grape marc adsorbent was effective in removing dyes from waste water. [ABSTRACT FROM AUTHOR]

One-pot condensation of pyrazole-4-aldehydes and hydroxylamine hydrochloride to form the corresponding oxime using formic acid as a medium and further dehydration of oxime using a catalytic amount of orthophosphoric acid to afford novel pyrazole-4-carbonitrile. This protocol serves as an ortho-phosphoric acid-catalyzed one-pot conversion of aldehyde to nitrile. Most remarkable features of this method are metal-free, cost-effective, atom efficiency with excellent yield (98–99%). This process will serve as a robust and scalable tool for the synthesis of valuable and versatile precursor (nitriles). This precursor will pave the way for the synthesis of various medicinally important valuable compounds. [ABSTRACT FROM AUTHOR]

The feasibility of preparing activated carbon by chemical activation from textile waste flax was studied. According to thermogravimetric analysis, H3PO4 and ZnCl2 changed the pyrolysis behavior of flax. Reactions between H3PO4 or ZnCl2 degradation intermediaries and flax resulted in flax carbonization and activation. The effects of activation temperature, time and impregnation ratio on yield, micropore, mesopore and elemental composition were discussed in detail. Results showed that the optimum activation temperature was 700 °C for H3PO4 and 800 °C for ZnCl2 while optimum activation time and impregnation ratio for both were 60 min and 1.0. H3PO4 activation was higher in yield while ZnCl2 activation obtained carbons that were higher both in surface area and mesopore volume. H3PO4 and ZnCl2 were able to carbonize the original flax components and produced activated flax that is highly carbonaceous, rich in surface functional groups and powdered in particle size. [ABSTRACT FROM AUTHOR]

A simple method has been developed for the estimation of uranium in reactor grade sodium without the removal of sodium using time gated luminescence with pulsed lamp. Samples are prepared after oxidizing the sodium in air followed by dissolution in H2SO4. Luminescence of uranium is measured in 2 M H3PO4 + 1 M H2SO4 medium. Using this method, the concentration of uranium in synthetic sodium sample was determined to be 0.2 µg/g. The limit of detection of uranium in bulk sodium was found to be 0.016 µg/g. [ABSTRACT FROM AUTHOR]

Activated carbon (AC) with high specific surface area was prepared by using bifunctional H3PO4 agent, which led to dehydrating and activation effects through hydrothermal pretreatment and subsequent pyrolysis process. N2 adsorption and desorption isotherms of AC showed a high BET surface area of 2434 m2 g−1 and a total volume of pores (VT) of 2.0447 m3 g−1 for AC. The morphology and the chemical components of hydrochar and AC were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy, which indicated that H3PO4 was benefitting for the formation of porous structure of AC. Subsequently, the effect of H3PO4 in hydrothermal pretreatment and activation process was investigated by comparative experiments. The removal and adsorption of methylene blue (MB) dye with different concentrations onto the AC were studied. The monolayer equilibrium adsorption capacity was 644 mg g−1, showing that AC has good adsorption qualities for methylene blue (MB). The adsorption balance data of MB on AC was best fitted to the Redlich-Peterson model. The adsorption kinetic data fit better to the pseudo-first-order model at low MB concentration, and the pseudo-second-order and Elovich models fit better when the MB concentration was rising. [ABSTRACT FROM AUTHOR]

Textile waste jute was activated by H3PO4 and ZnCl2 for reuse as activated carbon. Thermal degradation behavior of jute, impregnated jute and activating agents via thermogravimetric analysis were conducted first. Yield and iodine adsorption number were employed to determine the optimal activation conditions. As a result, activation by H3PO4 was best conducted at 700 °C for 90 min with an impregnation ration of 1.0 while conditions for ZnCl2 were 500 °C, 60 min and impregnation ratio of 1.0. That is, the best activation conditions varied with activating agents. So were the properties of resultant jute-based activated carbons. H3PO4 activation produced an activated carbon that was mostly mesoporous while that by ZnCl2 was more even in micropore and mesopore volumes as proven by pore volume distribution analysis. In addition, both carbons were abundant in surface functional groups which could be beneficial for adsorption of pollutants. Overall, jute could be effectively recycled to produce activated carbon that boasted excellent surface chemistry and textual properties. [ABSTRACT FROM AUTHOR]

series of activated carbon monoliths have been prepared by chemical activation of two lignocellulosic precursors, coconut shell (CACM) and African palm stones (PACM). The incorporation of a conforming step between the impregnation with HPO and the activation step allows the successful development of disc-shape monoliths without the use of a binder. Textural characterization results using N adsorption at 77 K show that the effect of the activating agent highly depends on the nature of the carbon precursor used. While chemical activation with phosphoric acid has mainly no effect when using coconut shell, a large development of both micro- and mesoporosity is observed for African palm stones. Large concentrations of the activating agent produce the partial shrinkage of the narrow microporous structure independently of the precursor used. Concerning the adsorption of CO at atmospheric pressure and 273 K, both series of activated carbon monoliths exhibit an improved adsorption behaviour with the activation degree up to an optimum value around ∼164 mg CO/g, for sample CACM-32, and ∼162 mg CO/g, for sample PACM-28, the amount adsorbed decreasing thereafter. Apparently, the total amount of CO adsorbed under these experimental conditions is defined by the volume of narrow micropores ( V). [ABSTRACT FROM AUTHOR]

AlMCM-41 materials with SiO2/Al2O3 molar ratios 20, 70, 110, 150, 200, and Si-MCM-41 were synthesized following standard procedures, and loaded with different amounts of H3PO4. The catalysts were well characterized by powder X-ray diffraction (XRD), nitrogen adsorption studies, and solid state 29Si, 27Al, 31P, 23Na and 1H MAS NMR spectroscopy. Acidity measurement by FT-IR spectroscopy monitoring of pyridine adsorption reveals that the incorporation of Al in the framework generates Brønsted and Lewis acidity, which increases with the increase in metal content. By loading H3PO4 on the AlMCM-41, Brønsted sites increases substantially, but the Lewis sites decrease to a large extent. Liquid phase isopropylation of naphthalene with isopropanol in n-hexane under autogeneous pressure was performed in the temperature range 473–623 K. The optimum feed molar ratio was found to be 1:2:10 (naphthalene:isopropanol: n-hexane), where the naphthalene conversion reaches to 85.5%. The β-and β,β-selectivities over 30 wt% H3PO4/AlMCM-41(200) were 97.0 and 84.8, respectively, at 85.5% conversion. The main products of the reaction, mono and diisopropylnaphthalenes, were analyzed and identified by gas chromatography and confirmed by GC–MS. The conversion and selectivity of the products are discussed from the point of view of catalyst characteristics and reaction conditions. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol (PVA)-based proton conducting polymer electrolytes have been prepared by the solution cast technique. The conductivity is observed to increase from 10−9 to 10−4 S cm−1 as a result of orthophosphoric acid (H3PO4) addition. The plot of conductivity vs temperature shows that a phase transition occurred at 343 K in the sample PVA-33 wt% H3PO4. The β-relaxation peak is observed at 313 K. The glass transition temperature of PVA-33 wt% H3PO4 is 343 K. Orthophosphoric acid seems to play a dual role, i.e., as a proton source and as a plasticizer. The ac conductivity σ ac = Aω s was also calculated in the temperature range from 303 to 353 K. The conduction mechanism was inferred by plotting the graph of s vs T from which the conduction mechanism for sample PVA-17 wt% H3PO4 was inferred to occur by way of the overlapping large polaron tunneling (OLPT) model and the conduction mechanism for the sample PVA-33 wt% H3PO4 by way of the correlated barrier height (CBH) model. [ABSTRACT FROM AUTHOR]

Isopiestic molalities of aqueous solutions of phosphoric acid have been measured at 383.15 to 523.15 K. NaCl(aq) served as the isopiestic standard for the calculation of osmotic coefficients. The ion-interaction model gave an excellent fit to the experimental osmotic coefficients by treating H3PO4(aq) as a 1–1 weak electrolyte. Activity coefficients, both real and stoichiometric, were also obtained from the analysis of the isopiestic results. As expected, the ionization of H3PO4(aq) decreased with increasing temperature. However, at higher molalities, the ionization increased with increasing molality (reionization). [ABSTRACT FROM AUTHOR]

The inhibiting properties of some organic phosphonium and ammonium compounds were studied with respect to the corrosion of zinc in 1 M H3PO4 solution. It was found that onium compounds which have π-electron system(s) are adsorbed following Frumkin's adsorption isotherm and provide better inhibition efficiency than those containing no π -electron system. The adsorption of the latter compounds was found to obey Langmuir's isotherm. Both potentiostatic and electrochemical impedance techniques proved that the studied onium compounds act as primary interface inhibitors without changing the mechanism of either hydrogen evolution reaction or zinc dissolution. [ABSTRACT FROM AUTHOR]

Wet etching has been widely used in defect evaluation for Ga-face GaN and surface roughness for N-face GaN dodecagonal pyramids has been fabricated on laser-lift-off N-face GaN by hot phosphor acid etching. The dodecagonal pyramid shows twelve facets including six {20-2-3} and six {22-4-5} planes. From cross-sectional TEM image, it is shown that the pyramid corresponds to the top of the edge dislocation. Compared with hexagonal pyramid-surface light emitting diodes (LEDs) etched by commonly used photoelectrochemical (PEC) process in KOH aqueous, the dodecagonal pyramid-surface LEDs show improved light extraction efficiency because of more facets, which effectively reduces the total internal reflection. [ABSTRACT FROM AUTHOR]

H3PO4, NaOH, and KOH solutions are found to be useful for removing nitrogen depleted layers or damage induced by high temperature annealing or dry etching of metalorganic chemical vapor deposition-grown (0001)GaN/Al2O3. Solutions are selective to the (0001)plane of GaN. However, certain flat planes etched without etch pits are exposed by wet etching. [ABSTRACT FROM AUTHOR]

Dry powder fire-extinguishing agent is one of Halon substitutes due to its superior fire-extinguishing performance, non-toxicity, and environmental friendliness. As one of the most widely used dry powders, ABC dry powder has attracted wide attention. Understanding its reaction mechanism is important to the design of more efficient compound dry powder based on it. When ABC dry powder was applied to the flame, ammonium dihydrogen phosphate (the main fire-extinguishing component of ABC dry powder) would rapidly decompose into phosphoric acid (H3PO4) and ammonia. Therefore, in order to figure out the chemical reaction mechanism of ABC dry powder and active radicals, the main focus of this paper is on the H3PO4. Analysis of the electrostatic potential on van der Waals surface of H3PO4 was carried out. Besides, detailed theoretical investigation has been performed on the mechanism, kinetics, and thermochemistry of the reactions of H3PO4 with H, OH, and CH3 radicals and further decomposition of H3PO4 using M06-2X/6-311G(d,p)//CCSD(T)/cc-pVTZ level of theory. Mayer bond order for all intrinsic reaction coordinate points was also calculated. Finally, it is theoretically proved that ABC dry powder extinguishes the fire mainly by chemical inhibition on H and OH radicals. [ABSTRACT FROM AUTHOR]