Waste activated sludge pretreatment by Fe(II)-activated peroxymonosulfate oxidation under mild temperature

The potential of Fe(II)-activated peroxymonosulfate (Fe(II)-PMS) oxidation under mild temperature applied to pretreat waste activated sludge (WAS) was investigated in this work. The reciprocal ratio of capillary suction time to its initial value (CST₀/CST) was used to characterize sludge dewaterability. The optimal conditions were Fe(II) 0.6 mmol g^?1 VSS, PMS 1.0 mmol g^?1 VSS, and temperature 60 °C, under which a high value of CST₀/CST was obtained to be 14.0 with a CST reduction rate of 92.9%. The enhancement of sludge dewaterability was mainly contributed from the remarkable increase of the negative zeta potential and the significant decrease of extracellular polymeric substances (EPS) (especially for protein). It was further observed that Fe(II)-PMS oxidation under mild temperature was beneficial to sludge disintegration in terms of VSS reduction and the concentrations of total organic carbon (TOC) and total nitrogen (TN) in the supernatant after treatment. Therefore, Fe(II)-PMS oxidation under mild temperature is a feasible and efficient alternative technology for sludge pretreatment.     

A synthesis of porous activated carbon materials derived from vitamin B9 base for CO2 capture and conversion

CO₂ capture and conversion are still a favorable way to reduce CO₂ in the atmosphere. Herein, we have developed an environmentally friendly, low energy consumption porous activated carbon from vitamin B9 carbonaceous material for CO₂ capture and conversion materials. It is demonstrated that the KOH/vitamin B9 carbonaceous material impregnation ratio of 2 is the optimum condition for obtaining porous activated carbons with high specific surface area of 1903 m²g^-1, micropore surface area of 710 m²g^-1, total pore volume of 1.05 cm³g^-1 and micropore volume of 0.38 cm³g^-1. Among all the porous activated carbons prepared, the porous activated carbon synthesized with the KOH/vitamin B9 carbonaceous material impregnation ratio of 2 registers the most excellent CO₂ capture for 5.41 mmolg^?1 at 0 °C/1 bar and 3.66 mmolg^?1 at 25 °C/1 bar. They can also effectively catalyze the cycloaddition of CO₂ and epoxides under mild conditions (1 bar, 100 °C and 8 h) with a yield of 89–94%. The synthesized porous carbon materials from vitamin B9 is a promising candidate material for CO₂ capture and fixation.     

Preparation of activated carbon from cotton stalk and its application in supercapacitor

High specific capacitance and low cost are the critical requirements for a practical supercapacitor. In this paper, a new activated carbon with high specific capacitance and low cost was prepared, employing cotton stalk as the raw material, by using the phosphoric acid (H₃PO₄) chemical activation method. The optimized conditions were as follows: the cotton stalk and activating agent with a mass ratio of 1:4 at an activation temperature of 800 °C for 2 h. The samples were characterized by nitrogen adsorption isotherms at 77 K. The specific surface area and pore volume of activated carbon were calculated by Brunauer–Emmett–Teller (BET) and t-plot methods. With these experimental conditions, an activated carbon with a BET surface area of 1,481 cm²?g^?1 and micropore volume of 0.0377 cm³?g^?1 was obtained. The capacitance of the prepared activated carbon was as high as 114 F?g^?1.The results indicate that cotton stalk can produce activated carbon electrode materials with low cost and high performance for electric double-layer capacitor.     

Equilibrium isotherms and isosteric heat for CO<Subscript>2</Subscript> adsorption on nanoporous carbons from polymers

Four nanoporous carbons obtained from different polymers: polypyrrole, polyvinylidene fluoride, sulfonated styrene–divinylbenzene resin, and phenol–formaldehyde resin, were investigated as potential adsorbents for carbon dioxide. CO₂ adsorption isotherms measured at eight temperatures between 0 and 60 °C were used to study adsorption properties of these polymer-derived carbons, especially CO₂ uptakes at ambient pressure and different temperatures, working capacity, and isosteric heat of adsorption. The specific surface areas and the volumes of micropores and ultramicropores estimated for these materials by using the density functional theory-based software for pore size analysis ranged from 840 to 1990 m² g^?1, from 0.22 to 1.47 cm³ g^?1, and from 0.18 to 0.64 cm³ g^?1, respectively. The observed differences in the nanoporosity of these carbons had a pronounced effect on the CO₂ adsorption properties. The highest CO₂ uptakes, 6.92 mmol g^?1 (0 °C, 1 atm) and 1.89 mmol g^?1 (60 °C, 1 atm), were obtained for the polypyrrole-derived activated carbon prepared through a single carbonization-KOH activation step. The working capacity for this adsorbent was estimated to be 3.70 mmol g^?1. Depending on the adsorbent, the CO₂ isosteric heats of adsorption varied from 32.9 to 16.3 kJ mol^?1 in 0–2.5 mmol g^?1 range. Overall, the carbons studied showed well-developed microporosity and exceptional CO₂ adsorption, which make them viable candidates for CO₂ capture, and for other adsorption and environmental-related applications.     

Preparation and methane adsorption of two-dimensional carbide Ti<Subscript>2</Subscript>C

Here a novel material for methane adsorption was synthesized and studied, which is a graphene-like two-dimensional (2D) carbide (Ti₂C, a member of MXenes), formed by exfoliating Ti₂AlC powders in a solution of lithium fluoride (LiF) and hydrochloric acid (HCl) at 40 °C for 48 h. Based on first-principles calculation, theoretically perfect Ti₂C with O termination has a specific surface area (SSA) of 671 m² g^?1 and methane storage capacity is 22.9 wt%. Experimentally, 2.85 % exfoliated Ti₂C with mesopores shown methane capacity of 11.58 cm³ (STP: 0 °C, 1 bar) g^?1 (0.82 wt%) under 5 MPa and the SSA was 19.1 m² g^?1. For Ti₂C sample intercalated with NH₃·H₂O, the adsorbed amount was increased to 16.81 cm³ (STP) g^?1 at same temperature. At the temperature of 323 K, the adsorbed amount of as-prepared Ti₂C was increased to 52.76 cm³ (STP) g^?1. For fully exfoliated Ti₂C, the methane capacity was supposed to be 28.8 wt% or 1148 V (STP)v^?1. Ti₂C theoretically has much larger volume methane capacity than current methane storage materials, though its SSA is not very high.     

Preparation of activated carbon from waste Camellia oleifera shell for supercapacitor application

The cost-effective activated carbons derived from waste Camellia oleifera shell (COS) by ZnCl₂ activation method are investigated as the active electrode material in electric double-layer capacitors (EDLCs) for the first time. The activation temperature and ZnCl₂/COS impregnation ratio are two key factors affecting the surface area and pore structure of the prepared activated carbons, which accordingly affect their capacitive performances. Electrochemical investigations indicate that the activated carbon (AC-3-600) obtained at the activation temperature of 600 °C and impregnation ratio of 3 shows the maximum specific capacitance of 374 and 266 F?g^?1 in 1 mol L^?1 H₂SO₄ and 6 mol L^?1 KOH electrolytes at 0.2 A g^?1, respectively. The high capacitance of the AC-3-600 is attributed to its high surface area (1,935 m² g^?1), high total pore volume (1.02 cm³ g^?1), and especially the large percentage of micropores (735 m² g^?1). Meanwhile, the activated carbon presents good cycle stability in both acid and alkaline electrolytes during 5,000 cycles at a fair current density of 4 A g^?1. So, we had reasons to believe that the activated carbons from waste COS by ZnCl₂ activation might be one of the innovative carbon electrode materials for EDLCs application.     

Enhanced Hydrolysis and Acidification of Waste Activated Sludge by Biosurfactant Rhamnolipid

The effect of biosurfactant rhamnolipid (RL) on hydrolysis and acidification of waste activated sludge (WAS) was investigated. The results indicated that RL could greatly reduce the surface tension of sludge, resulting in stimulating the hydrolysis rate of WAS and enhancing the production of short-chain fatty acids (SCFAs). With the increase of RL dosage from 0.2 to 0.5 g/g DS, the maximum soluble chemical oxygen demand (SCOD), protein and carbohydrate concentration increased correspondingly. After 6 h of hydrolysis, SCOD, protein and carbohydrate concentration increased from 371.9, 93.3 and 9.0 mg/l to 3,994.5, 800.0 and 401.4 mg/l at RL 0.3 g/g DS, respectively. Furthermore, the release of NH₄ ⁺-N, PO₄ ^3?-P and the accumulation of SCFAs also improved in the presence of RL. The maximum SCFAs was 1,829.9 mg COD/l at RL 0.3 g/g DS, while it was only 377.7 mg COD/l for the blank test. The propionic acid and acetic acid were the mainly SCFAs produced, accounting for 50–60% of total SCFAs.     

Adsorption of methyl orange using activated carbon prepared from lignin by ZnCl2 treatment

Lignocellulosic materials are good and cheap precursors for the production of activated carbon. In this study, activated carbons were prepared from the lignin at different temperatures (200 to 500°C) by ZnCl₂. The effects influencing the surface area of the resulting activated carbon are activation temperature, activation time and impregnation ratio. The optimum condition, are found an impregnation ratio of 2, an activation temperature of 450°C, and an activation time of 2 h. The results showed that the surface area and micropores volume of activated carbon at the experimental conditions are achieved to 587 and 0.23 cm³ g^?1, respectively. The adsorption behavior of methyl orange dye from aqueous solution onto activated lignin was investigated as a function of equilibrium time, pH and concentration. The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms. A maximum adsorption capacity of 300 mg g^?1 of methyl orange by activated carbon was achieved.     

Simultaneous thermal analysis of zirconium(IV) acetylacetonate in a helium atmosphere

TG, DTG, DTA, DDTA and ΔH analyses of zirconium(IV) acetylacetonate, Zr(C₆H₇O₂)₄ (= I), were performed in a helium atmosphere with a Netzsch Thermal Analyser STA 429. The enthalpies of the main steps of transformation were computed to be +42.182 J·g^?1 and ?21.113 J·g^?1. Pure I is thermally stable up to about 199°C in He gas, and melting too occurs at about 199°C. Four well-defined decomposition steps were observed over the range between ambient and 600 °C, accompanied by a weight loss of 61.59%. The final product contained pure ZrO. The unique shapes of the TG and DTA curves could be used for the identification of I.     

Fabrication and characterization of electrochemical double layer capacitors using ionic liquid-based gel polymer electrolyte with chemically treated activated charcoal electrodes

The present investigation deals with electrochemical double layer capacitors (EDLCs) made up of ionic liquid (IL)-based gel polymer electrolytes with chemically treated activated charcoal electrodes. The gel polymer electrolyte comprising of poly(vinylidine fluoride-co-hexafluropropylene) (PVdF-HFP)–1-ethyl-2,3-dimethyl-imidazolium-tetrafluroborate [EDiMIM][BF₄]–propylene carbonate (PC)–magnesium perchlorate (Mg(ClO₄)₂) exhibits the highest ionic conductivity of ~8.4?×?10^?3?S?cm^?1 at room temperature (~20 °C), showing good mechanical and dimensional stability, suitable for their application in EDLCs. Activation of charcoal was done by impregnation method using potassium hydroxide (KOH) as activating agent. Brunauer–Emmett–Teller (BET) studies reveal that the effective surface area of treated activated charcoal powder (1,515 m²?g^?1) increases by more than double-fold compared to the untreated one (721 m²?g^?1). Performance of EDLCs has been tested using cyclic voltammetry, impedance spectroscopy, and charge–discharge techniques. Analysis shows that chemically treated activated charcoal electrodes have almost triple times more capacitance values as compared to the untreated one.     

Dispersion of polymeric-coated–silica aerogel particles in unsaturated polyester composites: Effects on thermal-mechanical properties

The thermal-mechanical properties of unsaturated polyester (UP) composite were enhanced by the dispersion of silica aerogel (SA) with preserved pores. Low-cost SA was prepared from rice husk via the sol-gel process and ambient pressure drying. A new method was proposed to encapsulate the hydrophobic aerogel surface pores with hydrophilic polyvinyl alcohol (PVA) film using the fluidized-bed coating process. The dispersion of PVA-coated aerogel with preserved pores in the polyester matrix resulted in an increase of specific compressive strength (44.1?MPa?·?cm³?g^?1), thermal insulation (0.23?W?m^?1?K^?1), and thermal stability (T_onset?=?310°C), but decreased the glass transition temperature (T_g?=?260°C).     

No More HF: Teflon‐Assisted Ultrafast Removal of Silica to Generate High‐Surface‐Area Mesostructured Carbon for Enhanced CO2 Capture and Supercapacitor Performance

An innovative technique to obtain high‐surface‐area mesostructured carbon (2545 m² g^?1) with significant microporosity uses Teflon as the silica template removal agent. This method not only shortens synthesis time by combining silica removal and carbonization in a single step, but also assists in ultrafast removal of the template (in 10 min) with complete elimination of toxic HF usage. The obtained carbon material (JNC‐1) displays excellent CO₂ capture ability (ca. 26.2 wt % at 0 °C under 0.88 bar CO₂ pressure), which is twice that of CMK‐3 obtained by the HF etching method (13.0 wt %). JNC‐1 demonstrated higher H₂ adsorption capacity (2.8 wt %) compared to CMK‐3 (1.2 wt %) at ?196 °C under 1.0 bar H₂ pressure. The bimodal pore architecture of JNC‐1 led to superior supercapacitor performance, with a specific capacitance of 292 F g^?1 and 182 F g^?1 at a drain rate of 1 A g^?1 and 50 A g^?1, respectively, in 1 m H₂SO₄ compared to CMK‐3 and activated carbon.     

Preparation and properties of polymers with biphenyl units in the chain: Syntheses of solvent-soluble substituted polyphenylenes

Benzidinetetrazonium chloride (BTC)–CuCl and BTC–FeCl₂ complexes were thermally converted to benzene-soluble poly-4,4′-biphenylene plus small amounts of insoluble material. The soluble fraction was more stable than the insoluble fraction when heated at 300–500°C, although the solubility decreased. BTC in water was converted to an insoluble material by addition of alkali or cuprous ammonia solution. The C/(H + Cl) ratio indicated the existence of three to five side groups for each twenty phenyl groups of the insoluble fraction, while that of the soluble fraction showed few such groups. The number increased to one or more side groups for each phenyl nucleus as both soluble and insoluble fractions were heated to 500°C. A thin film of soluble fraction deposited on a copper plate showed an electrical conductivity in the range 10^?2–10^?3 ohm^?1 cm^?1 at 25°C and an energy gap (ΔE_g) of 0.2–0.3 eV. However, a compressed specimen of the same soluble fraction showed little conductivity. Solventsoluble samples of substituted poly-4,4,-biphenylene were prepared by the same procedure. These materials cracked on processing, and accurate conductivity measurements could not be made.     

Electrical conductivity of small ions in polyacrylonitrile in the glass–transition region

The electrical conductivity process in a new class of ion-containing polymers—highly concentrated solid solutions of hydrated perchlorate salts in polyacrylonitrile (PAN)—is described (σ_dc = 10^?7?10^?2Ω^?1cm^?1). A low-ac instrument (70 cps) is used to measure electrical conductivity. We present a cryogenic system in which the temperature dependence of the conductivity is studied (78–340°K). The ionic character of the conductivity process is established. The conductivity both above and below the glass-transition (T_g) point is thermally activated with an activation energy of 0.7–0.9 e V for the glassy state (?_g) and 0.12–0.6 eV for the rubber-like state (?_r). The systems described exhibit a compensation effect between the pre-exponential factor for the conductivity in the glassy state σ_0g and the difference in activation energy ?_g – ?_r      

Boron-incorporated Sulfonated polysulfone/polyphosphoric acid electrolytes for supercapacitor application

In the present work, boron-doped multicomponent gel polymer electrolytes composed of host polymer, sulfonated polysulfone (SPSU) and the additives; ionic liquid, 1-ethyl-3-methyl-imidazolium tetrafluoroborate (IL), H₃BO₃, polyphosphoric acid (PPA) were prepared. Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) techniques were used to characterize the sulfonated polysulfone-based electrolytes. Ion conductivity of these gel electrolytes were studied by dielectric impedance analyzer within the temperature from ?20 to 100°C. The ionic conductivity of the SPSU-5IL-1PPA and SPSU-5IL-1H₃BO₃-1PPA were measured as 4.8 × 10^?3 and 9 × 10^?4 S cm^?1, respectively. Supercapacitor having activated carbon-based composite electrode and electrolyte was constructed with the configuration: Al/C/electrolyte/C/Al. The electrochemical properties and ion transfer characteristics of the supercapacitor were investigated by the cyclic voltammetry (CV). Galvanostatic charge—discharge experiments exhibited good electrochemical reversibility and produced a specific capacitance value of 120 F g^?1 at 1 A g^?1. The symmetric supercapacitor system was retained almost 85% of its initial activity after 1000 cycle.     

Microstructure and protonic conductivity of H3PO4‐doped polyethylenimine–siloxane chemically covalently organic–inorganic hybrids

The chemically covalent polyethylenimine–siloxane hybrids doped with various amounts of ortho‐phosphoric acid (H₃PO₄) were prepared and characterized by FTIR, DSC, TGA, and solid‐state NMR spectra. The protonic conduction behavior of these materials was also investigated by means of impedance measurements. These observations indicate that the hydrogen bonding and protonic interactions exist between the dopant H₃PO₄ and the hybrid host, resulting in an increase in T _g of polyethylenimine segments. These hybrids are thermally stable up to 200 °C from TGA analysis. Conductivity studies show an Arrhenius behavior characteristic and the Grotthus‐like proton conduction, and a high conductivity of 10^?2–10^?3 S cm^?1 at 110 °C in dry atmosphere for the hybrid membrane with H₃PO₄/EI of 0.5. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 44: 2135–2144, 2006     

The production of activated carbon from cation exchange resin for high-performance supercapacitor

High-performance activated carbon for electrochemical double-layer capacitors (EDLC) has been prepared from cation exchange resin by carbonization and subsequent activation with KOH. The activation temperature has a key role in the determination of porous carbon possessing high surface areas, and large pore structures. The porous carbon activated at 700 °C (carbon-700-1:4) has high surface area (2236 m²?g^?1) and large total pore volume (1.15 cm³?g^?1), which also displays best capacitive performances due to its well-balanced micro- or mesoporosity distribution. In details, specific capacitances of the carbon-700-1:4 sample are 336.5 F?g^?1 at a current density of 1 A?g^?1 and 331.8 F?g^?1 at 2 A?g^?1. At high current density as 20 A?g^?1, the retention of its specific capacitance is 68.4 %. The carbon-700-1:4 sample also exhibits high performance of energy density (46.7 Wh?kg^?1) and long cycle stability (～8.9 % loss after 3,000 cycles). More importantly, due to the amount of waste ion-exchange resins increasing all over the world, the present synthetic method might be adopted to dispose them, producing high-performance porous carbons for EDLC electrode materials.     

On the mechanism of conductivity of ammonium salts

The conductivities of HSO₄^?-doped (NH₄)₂SO₄ (AS) and NH₄H₂PO₄ (ADP) crystals are investigated in the temperature range 25°?180°C. The mobility of the charge carriers (protons) is thermally activated and is expressed in accordance with the relation μ = 0.16 exp(?0.49) eV/kT and μ = 0.80 exp(?0.54 eV/kT)cm² V^?1 sec^?1 for AS and ADP crystals, respectively. Three-stage mechanism of proton transport in the lattice of ammonium salt is suggested: (1) formation of the charge carrier NH₄⁺ + X^? → NH₃ + HX, (2) reorientation of the protonated anion HX → XH, and (3) proton jump to the neighbor anion XH + X^? → X^? + HX. The activation energy for mobility is close to that for dielectric relaxation process, i.e., the only thermally activated stage in the mobility process is reorientation of the protonated anion. This very stage is also the rate-determining in the mobility as it is seen from the comparison of the correlation time for proton diffusion and the dielectric relaxation time. These experimental results are in good agreement with the known proton dynamic data in KDP-type ferroelectric crystals.     

Thermal analysis of a white calcium bentonite

A white calcium bentonite (CaB) taken from Çaml?dere (Ankara, Turkey) region was heated at various temperatures between 100 and 1100 °C for 2 h. The mineralogy of the CaB was determined as calcium smectite (CaS), metahalloysite (MH), opal-A (OA), opal-CT (OCT), quartz (Q), feldspar (F), and calcite (C) using the X-ray diffraction patterns of the natural CaB and its heated samples. Besides the XRD patterns, the thermogravimetry, differential thermal analysis, and low-temperature nitrogen adsorption (N₂-AD) data show that the CaS lose adsorbed and hydration water up to 300 °C, dehydroxylation takes place between 300 and 750 °C, and then the 2:1 layer structure completely collapses above 900 °C. The activation energies for the dehydration and dehydroxylation were calculated as 7636 and 48838 J mol^?1, respectively, from the TG data using Coats and Redfern method. The specific surface area (S) and specific micro–mesopore volume (V) obtained from N₂-AD data were 44 m² g^?1 and 0.100 cm³ g^?1 for the natural CaB. S and V reach their maxima of 105 m² g^?1 and 0.155 cm³ g^?1, respectively, at 300 °C, remain approximately constant as the temperature increases up to 700 °C and then decrease almost in parallel with each other, reaching their minima at 900 °C. This indicates that the S and V values increase gradually during dehydration and dehydroxylation of the CaS.     

METAL ADHESIVE PROPERTIES OF POLYAMIDES HAVING 4,5-DI(1,4-PHENYLENE)-IMIDAZOLEDIYL STRUCTURE

Polyamides were synthesized by the direct polycondensation of aromatic diamines containing 4,5-imidazolediyl structure with aliphatic dicarboxylic acids, and the metal adhesive properties of these polymaides were studied. The inherent viscosity of the obtained polyamides was in the range of 0.28 to 0.71 dl g^?1. The decomposition temperatures (T _ds) of the obtained polyamides were above 400°C and their glass transition temperatures (T _gs) were from 168 to 198°C. These polyamides also showed good solubilities in polar solvents, such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc) and formic acid. A standard tensile test was performed in order to examine the adhesive property of these polyamides for stainless steel, and the obtained polyamides showed excellent tensile strengths, e.g. polyamide P1s derived from 4,5-di(4-aminophenyl)imidazole (DAPI) and sebasic acid had values of 212 kgf cm^?2 at 20°C, 183 kgf cm^?2 at 120°C, and 133 kgf cm^?2 at 180°C. A commercially available epoxy resin was also examined, and showed great tensile strength at 20°C. However, the strength of the epoxy resin was found to decrease with increasing temperature, whereas polyamide having 4,5-imidazolediyl structure retains its strength at temperatures of up to 180°C. In addition, the polyamide was also derived from 4,4″-diamino-o-terphenyl(DAOT) (rather than DAPI) and sebasic acid, and the properties of the polyamides derived, respectively from DAPI and DAOT were compared.