Assessment of soil washing for Zn contaminated soils using various washing solutions

Bench-scale soil washing experiments were conducted to remove Zn from contaminated soils. Various washing solutions including hydrochloric acid (HCl), nitric acid (HNO₃), sodium hydroxide (NaOH), oxalic acid (HOOCCOOH·2H₂O), sulfuric acid (H₂SO₄), phosphoric acid (H₃PO₄), and tartaric acid (C₄H₆O₆) were used. The concentration of the washing solutions used in this study ranged from 0.1 M to 2 M with a liquid to solid ratio of 10. The soil washing results showed the following order of washing solution decreasing effectiveness for the removal of Zn: HCl > HNO₃ > H₂SO₄ > H₃PO₄ > C₄H₆O₆ > HOOCCOOH·2H₂O > NaOH.     

Optimization of desulphurization of Artvin–Yusufeli lignite with acidic hydrogen peroxide solutions

In this study in which the Taguchi method was used, the optimization of sulphur removal by H₂O₂/H₂SO₄ solutions was carried out over lignite with higher content of sulphur from Artvin/Yusufeli, Turkey. In experiments, the ranges of experimental parameters were between 0.25 and 6.0 mol L⁻¹ for H₂O₂ concentration, 0.25–4 mol L⁻¹ for H₂SO₄ concentration, 10–60 °C for reaction temperature, 0.01–0.08 g mL⁻¹ for solid-to-liquid ratio, 15–120 min for reaction time, 200–300 rpm for stirring speed and 710–120 μm for particle size. The optimum conditions for these parameters have found to be 60 °C of temperature, 0.06 g mL⁻¹ of solid-to-liquid ratio, 60 min of reaction time, 250 rpm of stirring speed and −250 + 180 μm of particle size.A statistical experimental arrangement, L₂₅(5⁶) was prepared to determine optimum sulphur removal and ash removal ratios. The obtained yields were 97.85% in removal of total sulphur, 56.54% in removal of pyritic sulphur, 21.33% in removal of organic sulphur and 61.52% in removal of ash. According to variance analysis, it was seen that all parameters were effective in removal of pyritic and total sulphur, reaction temperature, solid-to-liquid ratio, reaction time, stirring speed, H₂O₂ and H₂SO₄ concentrations in removal of organic sulphur, and other parameters except acid concentration in removal of ash.     

Influence of wet oxidation of herringbone carbon nanofibers on the pseudocapacitance effect

Herringbone carbon nanofibers (CNFs) were treated with concentrated HNO₃ and a mixture of diluted HNO₃/H₂SO₄ to obtain a series of oxygen enriched CNF with different oxygen group distribution, but with a similar porous texture. Oxygen functional groups were determined by X-ray photoelectron spectroscopy. CNFs with a very high relative concentration of carbonyl and/or quinone groups and hydroxyl groups were obtained by adjusting the suitable temperature and time of oxidation with HNO₃ and HNO₃/H₂SO₄, respectively. The electrochemical behavior of the samples was studied in three- and two-electrode cells. The performance of oxidized CNFs-based supercapacitors working in 1 mol L⁻¹ H₂SO₄ and 6 mol L⁻¹ KOH was analyzed using cyclic voltammetry and galvanostatic charging/discharging. The specific capacitance of the oxidized CNFs was more than twice enhanced in acidic and alkaline media compared to the pristine CNFs due to the pseudocapacitance effect. It was revealed that not only quinone groups but also hydroxyl groups contribute into the overall capacitance through the pseudocapacitance effect. With increasing surface concentration of the CO and C–OH groups, the capacitance values increase for the capacitors operating in both media.     

Adhesion improvement of electroless copper to PC substrate by a low environmental pollution MnO2–H3PO4–H2SO4–H2O system

A low environmental pollution etching system, MnO₂–H₂SO₄–H₃PO₄–H₂O colloid, was used to investigate surface etching performance of polycarbonate (PC) as a replacement for the chromic acid etching solution. The effects of H₂SO₄ concentrations, H₃PO₄ concentrations and etching times upon the surface topography, surface chemistry and surface roughness were studied. With the appropriate etching treatment, the surface average roughness (R_a) of PC substrates increased from 3 to 177 nm, and the adhesion strength between the electroless copper and PC substrate also reached 1.10 KN m⁻¹. After the etching treatment, the PC surface became hydrophilic and the surface contact angle decreased from 95.2° to 24.8°. The intensity of C–O groups increased and the new functional groups (–COOH) formed on the PC surface with the etching treatment, which improved the adhesion strength between PC substrate and elctroless copper film.     

Characteristics of the mercury vapor removal from coal combustion flue gas by activated carbon using H2S

Removal of Hg⁰ vapor from the simulated coal combustion flue gases with a commercial activated carbon was investigated using H₂S. This method is based on the reaction of H₂S and Hg over the adsorbents. The Hg⁰ removal experiments were carried out in a conventional flow type packed bed reactor system in the temperature range of 80–150 °C using simulated flue gases having the composition of Hg⁰ (4.9 ppb), H₂S (0–20 ppm), SO₂ (0–487 ppm), CO₂ (10%), H₂O (0–15%), O₂ (0–5%), N₂ (balance gas). The following results were obtained: in the presence of both H₂S and SO₂, Hg removal was favored at lower temperatures (80–100 °C). At 150 °C, presence of O₂ was indispensable for Hg⁰ removal from H₂S–SO₂ flue gas system. It is suggested that the partial oxidation of H₂S with O₂ to elemental sulfur (H₂S+1/2O₂=S_ad+H₂O) and the Clause reaction (SO₂+2H₂S=3S_ad+2H₂O) may contribute to the Hg⁰ removal over activated carbon by the following reaction: S_ad+Hg=HgS. The formation of elemental sulfur on the activated carbon was confirmed by a visual observation.     

Electrodeposited hybrid films of polyaniline and manganese oxide in nanofibrous structures for electrochemical supercapacitor

Hybrid films of polyaniline (PANI) and manganese oxide (MnO_x) were obtained through potentiodynamic deposition from solutions of aniline and MnSO₄ at pH 5.6. The hybrid films demonstrated characteristic redox behaviors of PANI in acidic aqueous solution. Characterization of the hybrid films by XRD indicated the amorphous nature of MnO_x in the films in which manganese existed in oxidation states of +2, +3 and +4, based on XPS measurement. Hybrid film of PANI and MnO_x, PM120 obtained from the solution of 0.1 M aniline and 120 mM Mn²⁺ displayed a well opened nanofibrous structure which showed an 44% increase in specific capacitance from that of PANI (408 F g^?1) to 588 F g^?1, measured at 1.0 mA cm^?2 in 1 M NaNO₃ (pH 1). The hybrid film kept more than 90% of its capacitance after 1000 charging-discharging cycles, with a coulombic efficiency of 98%. The specific capacitance of a symmetric capacitor using PM120 as the electrodes is 112 F g^?1.     

Activation of graphene aerogel with phosphoric acid for enhanced electrocapacitive performance

We present a facile and efficient route to introduce in-plane nanopores on the graphene sheets by activation of graphene aerogel (GA) with phosphoric acid (H₃PO₄). Results from N₂ adsorption and TEM images showed that H₃PO₄ activation created mesopores with pore size of 2–8 nm on the graphene sheets. With such nanopores on graphene sheets, the activated GA exhibits a specific capacitance of 204 F g⁻¹, enhanced rate capability (69% capacitance retention from 0.2 to 30 A g⁻¹), reduced equivalent series resistance (3.8 mΩ) and shortened time constant (0.73 s) when comparing with the hydrothermally-derived pristine GA and thermally annealed GA in the absent of H₃PO₄. The excellent capacitive properties demonstrate that introduction of nanopores on GA by H₃PO₄ activation not only provides large ion-accessible surface area for efficient charge storage, but also promotes the kinetics of electrolyte across the graphene two-dimensional planes.     

Characterization and AC conductivity of polyaniline–montmorillonite nanocomposites synthesized by mechanical/chemical reaction

Polyaniline–clay nanocomposites were prepared by solid state polymerization of aniline chloride in the interlayer of montmorillonite through the use of persulfate of ammonium as oxidant. The proportion of aniline to clay and the molar ratio of oxidant to aniline are being varied. The analyse of UV visible and FTIR spectroscopy demonstrated that aniline has been polymerized to polyaniline (PANI) in its conducting emeraldine form. The conformation adopted by PANI chains in the clay interlayer depended on the molar ratio of aniline to montmorillonite. Thermogravimetric analysis of the nanocomposites suggested that polyaniline chains are more thermally stable than those of free polyaniline prepared by solid–solid reaction. The AC conductivity data of different synthesized nanocomposites were analyzed as a function of frequency. Low frequency conductivities of polyaniline/montmorillonite nanocomposites materials ranges from 0.18 to 5.6 × 10^?3 S/cm. All characterization data were compared to those of free polyaniline that was synthesized using a solid–solid reaction.     

Liquid phase catalytic dehydration of glycerol to acrolein over Brønsted acidic ionic liquid catalysts

Liquid phase dehydration of glycerol to acrolein catalyzed by Brønsted acidic ionic liquids (BAILs) using semi-batch reaction technique was investigated. For the BAILs catalysts, the acrolein yields were in an order of [Bmim]H₂PO₄ > [Bmim]HSO₄ > [BPy]HSO₄ > [PSPy]HSO₄ > [N₂₂₂₄]HSO₄ > [PSPy]H₂PO₄ > [BPy]H₂PO₄ > [N₂₂₂₄]H₂PO₄. When [Bmim]H₂PO₄ and [Bmim]HSO₄ were used as the catalysts at 270 °C with the molar ratio of catalyst to glycerol of 1:100, the acrolein yields were 57.4% and 50.8%, respectively, at complete conversion of glycerol. The BAILs with [Bmim] cation and moderate acidity favored the formation of acrolein in liquid phase glycerol dehydration.     

A new dual luminescent pillared cerium(IV)sulfate–diphosphonate

A new pillared cerium(IV) sulfate–diphosphonate with formula Ce₂(2H₂O)[(O₃PCH₂)–NC₁₀H₁₈N–(CH₂PO₃)(SO₄)₂] · 6H₂O has been hydrothermally synthesized and its structure has been solved ab initio from laboratory X-ray powder diffraction data.The luminescent and thermal properties of this compound have been preliminarily studied and the encouraging results place it in the field of functional hybrid materials.     

SO42−–Mn–Co–Ce supported on TiO2/SiO2 with high sulfur durability for low-temperature SCR of NO with NH3

The catalysts SO₄^2 − Mn–Co–Ce/TiO₂/SiO₂ were investigated for the low-temperature SCR of NO with NH₃ in the presence of SO₂. An excellent SO₂ durability at low temperature was obtained with the catalyst used TiO₂/SiO₂ as support and modified with SO₄^2 −. The catalyst sulfated with 0.1 mol/L H₂SO₄ solution and then calcined at 300 °C exhibited the best NO_x conversion efficiency of 99.5% at 250 °C in the presence of 50 ppm SO₂. The conversion efficiency did not decrease after repeatedly used for 8 times.     

Proton conductive YSZ-phosphate composite electrolyte for H2S SOFC

A new oxide-salt composite electrolyte, YSZ–K₃PO₄–Ca₃(PO₄)₂, shows proton conductivity in the order of 10^?2 S/cm at 700 °C. The proton transport number, determined using a hydrogen concentration cell, rises from more than 93% at 550 °C to 99% at 700 °C. The composite electrolyte is chemically stable in H₂S containing atmosphere, and so is a good candidate electrolyte material for H₂S solid oxide fuel cells applications.     

Biodiesel production from waste cooking oil in a microtube reactor

Waste cooking oil (WCO) was used to produce biodiesel in a microtube reactor. First, the acid value of the WCO was reduced from 3.96 mg KOH/g to less than 1 mg KOH/g via acid catalyzed esterification. The effects of the methanol-to-WCO molar ratio (4.5:1–18:1), the H₂SO₄ concentration (0.5–2 wt.%), reaction temperature (55–70 °C), and reaction time (5–20 s) were studied. The optimal conditions were 9:1 methanol-to-WCO molar ratio, 1 wt.% H₂SO₄, 65 °C and 5 s of reaction time. Triglycerides in the product from the first step were transesterified with methanol and alkaline catalyst. Methyl ester content of the biodiesel was 91.76%.     

Construction of two 2D 3d-4f coordination complexes based on the linkages of left-and right-handed helical chains

Two transition-lanthanide metal-organic coordination polymers, {[CoLn₂(Himdc)₂(SO₄)₂(H₂O)₄]·H₂O}_n [Ln = Yb (1), Ho (2)] (H₃imdc = imidazole-4, 5-dicarboxylic acid), have been synthesized by the hydrothermal reactions of lanthanide oxides, CoSO₄·7H₂O, H₃imdc and H₂O. Single-crystal X-ray diffraction analysis reveals that the isostructural complexes 1 and 2 possess unusual 2D wave-like heterometallic layers with 1D (Ln₂O₂CoO₂)_n and [Ln₂(SO₄)₂]_n inorganic chains constructed by the assembly of 1D left-/right-handed helical L–Ln₂Co–L (L = Himdc) chains and SO₄^2? anions, while a 3D framework is formed via hydrogen-bonding interactions interlayer.     

Two trimeric tri-TiIV-substituted Keggin tungstogermanates based on tetrahedral linkers

Two trimeric nine-Ti^IV contained tungstogermanates K₁₄{K ⊂ [(Ge(OH)O₃)(GeW₉Ti₃O₃₈H₂)₃]} · 42H₂O 1 and K₁₀{K ⊂ [(SO₄)(GeW₉Ti₃O₃₈H₃)₃] · 40H₂O 2 have been conventionally synthesized and characterized by elemental analysis, IR, TG and single-crystal X-ray diffraction. They were constructed from three tri-substituted A-α-[GeW₉Ti₃O₃₈] and GeO₄/SO₄ tetrahedral linker. They display the first example of trimeric titanium-substituted tungstogermanates, which contain both Ti–O–Ti and Ti–O–Ge/Ti–O–S bridges.     

Study effect of different parameters on the sulphate sorption onto nano alumina

The aim of this research work is to investigate sorption characteristic of modified nano alumina (n-Al) for the removal of SO₄^2? from aqueous solutions and wastewater. The sorption of SO₄^2? by batch method is carried out. The optimum conditions of sorption were found to be: a sorbent dose of 0.3 g in 100 ml of SO₄^2?, contact time of 35 min, pH = 5. In optimum condition, removal efficiency was 85.6% for the SO₄^2?. Three equations, i.e. Morris–Weber, Lagergren and pseudo second order have been tested to track the kinetics of removal process. The Langmuir, Freundlich and D–R are subjected to sorption data to estimate sorption capacity. It can be concluded that n-Al has potential to remove SO₄^2? ions from aqueous solutions at different concentrations. It was found that the temperature has positive effect on the process and negative ΔG values indicated thermodynamically feasible and spontaneous nature of the sorption. Positive value of ΔS reveals the increased randomness at the solid–solution interface during the fixation of the ion on the active sites of the sorbent. The effect of other anions was studied and it was found the existence of them in the solution has considerable effect on the sulphate removal.     

A novel approach to mesoporous anatase TiO2: Oxidation of TiC by nitric acid

TiO₂ has been prepared by a novel, mild one-step reaction between TiC and aqueous HNO₃ at 70 °C. This material possesses an anatase crystal form and a narrow pore-size distribution of mesoporous channels. The BET surface area, average pore diameter, and total pore volume are 332.7 m²/g, 3.28 nm, and 0.23 cm³/g, respectively. Our method is a template-free synthesis process, distinct from sol–gel methods for mesoporous TiO₂ fabrication using structure-directing surfactants or polymers. TiO₂ is not generated from TiC reacting with other acids and oxidants, such as HCl, H₂SO₄, H₃PO₄, KMnO₄, K₂Cr₂O₇, Na₂S₂O₇, H₂O₂, and Na₂CrO₄, at a similar reaction condition. Since the average particle size of the mesoporous TiO₂ produced is much larger than that of the TiC starting material, the mechanism for the formation of the mesoporous TiO₂ is not via mesopore-etching of TiC particles and transformation of TiC pore walls into TiO₂ by HNO₃. It is likely that TiC is first transformed into Ti_mX_n species, followed by hydrolysis to form mesoporous TiO₂.     

Mullite whiskers derived from kaolin

Short mullite whiskers prepared by firing compacts of kaolin and NH₄Al(SO₄)₂·12H₂O powders, with a small addition (0.8, 1.5 wt%) of NaH₂PO₄·2H₂O, in air 1300 and 1400 °C for 15 h have been characterized in terms of whisker morphology, composition and structure. Relatively uniform whisker shaped crystals grew within the silicate glass matrix. After chemically leaching the glass matrix with HF solution using a microwave heating source, the resulting whiskers were exposed as isolated crystals and exhibited an aspect ratio of >17 (～0.5 μm in diameter). The mullite whiskers had a composition of 51.06 mol% Al₂O₃ and 48.94 mol% SiO₂, with an orthorhombic crystallographic structure.     

Solvent-free synthesis of new metal phosphate-oxalates with helical-chain and slablike structures

Two metal phosphate-oxalate, namely, H₃pmdeta ⋅ Ga₂(HPO₄)(H₂PO₄)(C₂O₄)₃ (1) and H₂mpip ⋅ Mn₂(H₂PO₄)₂(C₂O₄)₂ ⋅ H₂O (2), were prepared under solvent-free conditions, where pmdeta = N′,N″,N″-pentamethyldiethylenetriamine and mpip = 1-methylpiperzaine. Compound 1 features a helical-chain structure containing cyclic inorganic building block. Compound 2 has a slablike structure with a kgd net. The magnetic and proton-conducting properties of compound 2 were also investigated.     

High voltage supercapacitor built with seaweed carbons in neutral aqueous electrolyte

High oxygen content (10–15 at.%) nanotextured carbons were obtained by pyrolysis of seaweeds at 600–750 °C and applied as electrodes for supercapacitors in H₂SO₄, KOH and Na₂SO₄ aqueous media. Interestingly, the potential stability window measured in a three-electrode cell configuration depends both on the nature of the oxygenated surface functionality and on the electrolyte pH. A high value of 2.4 V was observed in Na₂SO₄ for the seaweeds pyrolysed at 600 °C, showing that the surface functionality strongly influences the over-potentials of di-hydrogen evolution and carbon oxidation. Symmetric capacitors built from the seaweed carbons exhibited an excellent cycle life for voltage values up to 1.6 V, showing the promise of Na₂SO₄ for developing high energy density and environment friendly systems.