Alkali Washing Research Articles

Surfactant-free synthesis of hollow mesoporous carbon spheres and their encapsulated Au derivatives using biopolymeric chitosan

To realize surfactant-free synthesis of biomass-derived hollow mesoporous carbon spheres and their derivatives, choice of synthetic methodology and carbon precursor is crucial. Herein, a brand-new hollow mesoporous carbon sphere (HMCS) is first synthesized from 8-quinolinol modified chitosan via an in situ stöber templating approach without surfactant followed by pyrolysis and alkali washing. The resultant HMCS is uniform, and shows a cavity size of 417 nm, a shell thickness of 5 nm, and a narrow mesopore size distribution centered at 3.9 nm. The HMCS is then upgraded by encapsulation of a single Au nanocrystal (NC) into the void of HMCS to form a yolk-shell architecture, YS-Au@HMCS. Its cavity size and shell thickness are decreased to 187 and 3 nm, while the mesopore size is increased to 4.3 nm, the surface area (215 m2 g−1) and mesoporosity (74.7%) are triple and twice that of HMCS, respectively, just by halving the delay time of carbon source addition. Owing to the unique hollow interiors and mesopores, as well as their synergism with the encapsulated Au NCs, the elaborately fabricated YS-Au@HMCS exhibits appealing catalytic performances towards the deposal of sewage. It delivers a large activity factor of 34.32, 13.29 and 0.05 s−1 g−1 in the reduction of 4-nitrophenol and methylene blue using sodium borohydride, and in the photodegradation of methylene blue under visible light irradiation, respectively. These advances shed new light on the synthesis of hollow mesoporous carbon spheres and the designed synthesis of functional carbon materials with versatile applications.

Identification of diluent degradation products in radiolyzed PUREX solvent

ABSTRACTDiluent degradation products in gamma radiolyzed Plutonium URanium Extraction (PUREX) solvent were characterized, under the conditions similar to those prevailing in the hot cell for reprocessing. Alkali wash of the degraded solvent followed by vacuum distillation resulted in primary separation. Column separation of the distillation residue followed by spectroscopic analysis using GC-MS and NMR revealed the residue predominantly to be a mixture of dodecan-3-ol, dodecan-4-ol, and dodecan-5-ol in the ratio of 2:1:6, respectively and a mixture of 2-nitrododecane, 3-nitrododecane, 4-nitrododecane, and 5-nitrododecane in the ratio of 2:2:1:1, respectively. The identified compounds were confirmed by synthesizing them individually and comparing their spectral data.

Novel Methodology for the Isolation of Pure Piperine from Plant Source through Sonication

Piperine was discovered in 1819 by Hans Christian, who isolated it from the fruits of Piper nigrum, the source plant of both the black and white pepper grains [1]. Fluckiger and Hanbury found piperine in Piper longum and Piper officinarum Piperine, along with its isomer chavicine, is the alkaloid[1b] responsible for the pungency of black pepper and long pepper [2]. Piperine is extracted from black pepper using dichloromethane [3]. Aqueous hydrotropes can be used in the extraction to result in high yield and selectivity [4]. The amount of piperine varies from 1-2% in long pepper, to 5-10% in commercial white and black peppers [5]. Further, it may be prepared by treating the solvent-free residue from an alcoholic extract of black pepper, with a solution of potassium hydroxide to remove resin (said to contain chavicine, an isomer of piperine) and solution of the washed, insoluble residue in warm alcohol, from which the alkaloid crystallises on cooling [6]. It has been used in some forms of traditional medicine. Piperine, a major alkaloid in black pepper is one of the most gifted bioenhancers till date. Additional methods used for its isolation suffer disadvantages such as poor extraction efficiency, tedious and pricey isolation methodology, piperine photode gradation, etc. Hence a simple, rapid and well-organized method has been developed for the extraction of piperine from the fruits of Piper nigrum. The methods under study involve extraction of piperine with various solvents such as ethanol, propionic acid and dichloromethane. Then isolation and purification were followed by separate classical methods for respective extracts. Compared to other two methods, the novel method using propionic acid proved to be valuable in isolating piperine with higher yield and in higher purity. Hence extract derived using propionic acid was further subjected to alkali wash and passing out through small silicagel bed. Then identification of the compound was confirmed by various analytical methods TLC, melting point, UV-visible spectrophotometer, FT-IR, HPLC and compared it with authentic piperine which resulted into better pure piperine crystals as that of authentic piperine.

A prototype of novel agro-waste based column bed device for removal of textile dye Optilan Red.

The aim of the study was to assess the potentiality of an agro-waste (sugarcane bagasse) for removal of the textile dye (Optilan Red) using novel column based filtration unit with a packed column of chemically treated sugarcane bagasse. The treated and untreated sugarcane bagasse (biosorbent) were characterized by Fourier transform infrared (FT-IR) spectroscopy. Effect of initial dye concentration on percentage removal of dye, equilibrium adsorption of sugarcane bagasse, kinetic studies, breakthrough point equilibrium and desorption of dye from the column material were studied. An inverse dependence of initial dye concentration on percent removal of dye was observed, whereas the equilibrium adsorption (qe) showed a direct relationship with dye concentration. The time required for reaching breakthrough point was 120 min. Desorption of dye through alkali wash resulted in complete desorption after 1 h washing of the column for its reuse for next cycle. FT-IR analysis shows vibration in valence bands of the hydrogen bond of OH group, and the bands of intra-molecular and intermolecular hydrogen bonds, which results in interaction of treated bagasse with Optilan Red textile dye. The present study showed that more than 93% removal of the dye can be achieved in the concentration range 10-50 ppm (aqueous solution). The removal efficiency of the column remained almost unchanged for the treatment of dye-house wastewater spiked with the dye. The agro-waste based treatment process shows a considerable potential for a low-cost treatment of dye contaminated water.

Removal of fluorine ions from industrial zinc sulfate solution by a layered aluminum-based composite

The layered aluminum-based composite which was synthesized by co-precipitation followed by calcining the precursor at 450°C under N2 atmosphere has been used to remove fluorine ion from industrial zinc sulfate solution. The composite was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and BET specific surface area analysis. The effect of adsorption temperature, dosage of absorbent, contact time and the adsorption kinetics were investigated. The kinetics data suggests that the process of adsorption could be described by the pseudo-second-order kinetic model. The adsorption isotherm fits the Langmuir isotherm model well and the theoretical maximum adsorption capacity was 5.62mg/g. Furthermore, the adsorption mechanism was studied by Energy dispersive analysis of X-ray (EDX) and Fourier transform infrared spectroscopy (FTIR). The result shows that the distribution of F element is associated with Al element after adsorption and the hydroxyl could exchange with fluorine ion, revealing an ion exchange mechanism. The regeneration study shows that the adsorbent could be reused by a simple method of Alkali washing followed by pickling.

Improvement of Gold Leaching from a Refractory Gold Concentrate Calcine by Separate Pretreatment of Coarse and Fine Size Fractions

A total gold extraction of 70.2% could only be reached via direct cyanidation from a refractory As-, S- and C-bearing gold concentrate calcine, and the gold extraction varied noticeably with different size fractions. The reasons for unsatisfactory gold extraction from the calcine were studied through analyses of chemical composition, chemical phase and SEM-EDS of different sizes of particles. It was found that a significant segregation of compositions occurred during the grinding of gold ore before flotation. As a result, for the calcine obtained after oxidative roasting, the encapsulation of gold by iron oxides was easily engendered in finer particles, whilst in coarser particles the gold encapsulation by silicates was inclined to occur likely due to melted silicates blocking the porosity of particles. The improvement of gold leaching from different size fractions was further investigated through pretreatments with alkali washing, acid pickling or sulfuric acid curing-water leaching. Finally, a novel process was recommended and the total gold extraction from the calcine could be increased substantially to 93.6% by the purposeful pretreatment with alkali washing for the relatively coarse size fraction (+37 μm) and sulfuric acid curing–water leaching for the fine size fraction (−37 μm).

Valorization of stainless steel slag by selective chromium recovery and subsequent carbonation of the matrix material

This study focuses on the recycling of stainless steel (SS) slags containing about 1.2 wt% of chromium (Cr). The selective recovery of Cr from SS slag by a hydrometallurgical method (alkaline pressure leaching) was investigated. Leaching experiments were carried out based on 24−1 factorial design of experiment (DOE) with the following parameters: NaOH concentration, temperature, leaching time, and mechanical activation (MA). Results show that temperature and MA are the most influencing factors for an enhanced Cr leaching. The maximum Cr leaching was 46% at 1 M NaOH, 240 °C, 6 h, MA 30 min, while the matrix material was dissolved only to a limited extent (Al 2.88%, Si 0.12%, Ca 0.05%). After Cr leaching followed by alkali washing, a carbonation treatment is proposed to stabilize the remaining Cr in the matrix material and make the subsequent recycling of the matrix material as a construction material possible.

Hydrogen storage properties and mechanisms of magnesium based alloys with mesoporous surface

A new kind of magnesium based hydrogen storage alloy with highly developed surface (HDS) was prepared using the technique of mechanical alloying followed by alkali washing in this paper. The phase composition, morphology, hydrogen storage properties and mechanisms of the alloy thus prepared, named HDS Mg-Ni, were further investigated by multiple methods including X-ray diffraction, scanning electron microscope, Sieverts volumetric method and differential scanning calorimeter. The specific surface area, average pore size and pore volume of the alloy are 50.95 m2 g−1, 36.2 nm and 0.34 cc g−1, respectively. Also, it was discovered that the HDS Mg-Ni powder takes in about 0.65 wt.% of hydrogen even at a low temperature of 323 K, at which the conventional Mg and Mg2Ni materials could not react with H2. It suggests that the highly developed surface remarkably improves the hydrogen storage properties at low temperatures. Besides, the synergistic effects between the HDS Mg-Ni powder and activated carbon(AC) on the improvement of low-temperature behaviors were discussed. The results showed that the addition of AC further improves the hydrogen capacity and absorption kinetics due to the increased specific surface area, providing easier and more paths for the diffusion of hydrogen into the alloy powder.

Low temperature selective catalytic reduction of NO<sub>x</sub> with NH<sub>3</sub> over Mn-based catalyst: A review

The removals of NOx by catalytic technology at low temperatures (100–300 °C) for industrial flue gas treatment have received increasing attention. However, the development of low temperature catalysts for selective catalytic reduction (SCR) of NOx with ammonia is still a challenge especially in the presence of SO2. The current status of using Mn-based catalysts for low temperature SCR of NOx with ammonia (NH3-SCR) is reviewed. Reaction mechanisms and effects of operating factors on low temperature NH3-SCR are addressed, and the SCR efficiencies of Mn-based metal oxides with and without SO2 poisoning have also been discussed with different supports and co-metals. The key factors for enhancing low temperature NH3-SCR efficiency and SO2 resistance with Mn-based catalysts are identified to be (1) high specific surface area; (2) high surface acidity; (3) oxidation states of manganese; (4) well dispersion of manganese oxide metals; (5) more surface adsorbed oxygen; (6) more absorbed NO3− on the catalyst surface; (7) easier decomposition of ammonium sulfates. Moreover, the regenerative methods such as water washing, acid and/or alkali washing and heat treatment to the poisoned catalysts could help to recover the low temperature SCR efficiency to its initial level.

Advanced treatment of municipal wastewater by nanofiltration: Operational optimization and membrane fouling analysis

Municipal sewage from an oxidation ditch was treated for reuse by nanofiltration (NF) in this study. The NF performance was optimized, and its fouling characteristics after different operational durations (i.e., 48 and 169hr) were analyzed to investigate the applicability of nanofiltration for water reuse. The optimum performance was achieved when transmembrane pressure=12bar, pH=4 and flow rate=8L/min using a GE membrane. The permeate water quality could satisfy the requirements of water reclamation for different uses and local standards for water reuse in Beijing. Flux decline in the fouling experiments could be divided into a rapid flux decline and a quasi-steady state. The boundary flux theory was used to predict the evolution of permeate flux. The expected operational duration based on the 169-hr experiment was 392.6hr which is 175% longer than that of the 48-hr one. High molecular weight (MW) protein-like substances were suggested to be the dominant foulants after an extended period based on the MW distribution and the fluorescence characteristics. The analyses of infrared spectra and extracellular polymeric substances revealed that the roles of both humic- and polysaccharide-like substances were diminished, while that of protein-like substances were strengthened in the contribution of membrane fouling with time prolonged. Inorganic salts were found to have marginally influence on membrane fouling. Additionally, alkali washing was more efficient at removing organic foulants in the long term, and a combination of water flushing and alkali washing was appropriate for NF fouling control in municipal sewage treatment.

ChemInform Abstract: Advancement in Heterogeneous Base Catalyzed Technology: An Efficient Production of Biodiesel Fuels

AbstractReview: 199 refs.

Covariance-based locally weighted partial least squares for high-performance adaptive modeling

Locally weighted partial least squares (LW-PLS) is one of Just-in-Time (JIT) modeling methods; PLS is used to build a local linear regression model every time when output variables need to be estimated. The prediction accuracy of local models strongly depends on the definition of similarity between a newly obtained sample and past samples stored in a database. To calculate the similarity, the Euclidean distance and the Mahalanobis distance have been widely used, but they do not take account of the relationship between input and output variables. This fact limits the achievable performance of LW-PLS and other locally weight regression methods. Thus, in the present work, covariance-based locally weighted PLS (CbLW-PLS) is proposed by integrating LW-PLS and a new similarity index based on the covariance between input and output variables. CbLW-PLS was applied to two industrial problems: soft-sensor design for estimating unreacted NaOH concentration in an alkali washing tower in a petrochemical process, and process analytical technology (PAT) for estimating concentration of a residual drug substance in a pharmaceutical process. The proposed similarity index was compared with six conventional indexes based on distances, correlations, or regression coefficients. The results have demonstrated that CbLW-PLS achieved the best prediction performance of all in both case studies.

Advancement in heterogeneous base catalyzed technology: An efficient production of biodiesel fuels

Price fluctuation of petroleum-based diesel, climate change, emerging mandate obligations, availability of new feedstock and the upgrading of conversion technologies are expected to drive biodiesel market to grow robustly in the next coming 10 years. However, the current bottleneck in biodiesel production is the lack of economical sustainable conversion technologies. Generally, industrial production of biodiesel is greatly relied on alkaline homogeneous transesterification reaction. Limitation of the technology, such as multistep process which incur extra pre-step for high acid oil treatment and post-step for biodiesel purification and alkali washing as diminished the economic feasibility and low environmental impact of the entire biodiesel process. Heterogeneous catalysis offers immense potential to develop simple transesterification process, including one step reaction, easy separation, reusability of catalyst, and green reaction. Thus, the aim of this paper is to review the biodiesel production technologies such as blending, micro-emulsion, pyrolysis, and transesterification. Furthermore, recent studies on heterogeneous catalyzed transesterification were presented by discussing the issues such as catalytic performance on different types of biodiesel feedstock, transesterification reaction conditions, limitations encountered by heterogeneous catalysts, and reusability of solid catalysts. The heterogeneous catalysts presented in this review is mainly focused on solid base catalysts, which include single metal oxides, supported metal oxide, binary metal oxide, hydrotalcite, and natural waste shell-based catalyst. Furthermore, current perspectives on application of heterogeneous catalyzed technology in biodiesel industry were discussed herein.

Removal of reactive dyes using a high throughput-hybrid separation process

Toxic and carcinogenic reactive dyes are abundantly used in textile industries due to their wide variety of colour and texture. In this study, a hybrid separation process was used to remove four common reactive dyes (reactive yellow, red, black and brown) from aqueous solution. Synthetic solution of these dyes was subjected to adsorption by activated carbon followed by microfiltration (MF), using a ceramic membrane module. Dyes were completely removed by adsorption at pH 4.5 and the dye-loaded adsorbents were removed by cross-flow MF. Maximum Langmuir adsorption capacity of activated carbon for these four dyes was in the range of 88–106 mg/g. Effects of trans-membrane pressure drop and cross-flow rate on the throughput of the combined process was investigated. Membrane fouling was due to the cake type of layer formed by the activated carbon particles. Five different washing protocols were tested for their efficiency and the acid–alkali wash was found to be the most effective.

Parameter optimization based on capacitive deionization for highly efficient desalination of domestic wastewater biotreated effluent and the fouled electrode regeneration

Capacitive deionization (CDI) has gradually become an alternative desalination technique due to its many merits in comparison to conventional approaches. A novel optimized CDI device based on common carbon electrode has been developed successfully considering economics and efficiencies of CDI for the practical application. The optimized parameters of CDI have been obtained by adjusting the experimental conditions. The proposed results are 1.8V of applied potential, 2mm of plate distance and 15mL/min of flow rate. Besides, the adsorption process was in accordance with Lagergren equation and Langmuir isothermal equation. Moreover, the carbon electrode exhibited the excellent regeneration performance by desalting the domestic wastewater biotreated effluent, which would permit the recycling of CDI device. It is notable that some dissolved organic matters (DOMs) existing in waste water, such as humic acid, would decrease its desalination and regeneration performances. Fortunately, the generation and mechanism of electrode pollution were analyzed by advanced detecting instruments, such as three-dimensional fluorescence and Gel Permeation Chromatograph. During the treating process of regeneration, we found that the fouled carbon electrodes could be cleaned up by alkali washing instead of water or acid. The results provided in this paper would guide the practical application of CDI effectively.

Solvent extraction studies with some fission product elements from nitric acid media employing tri-iso-amyl phosphate and tri-n-butyl phosphate as extractants

Tri-iso-amyl phosphate (TiAP) has been identified as an alternate extractant to tri-n-butyl phosphate (TBP) for the reprocessing of fast reactor fuels. In the present work, extraction behaviour of some fission product elements such as Zr(IV), RuNO(III), \( {\text{TcO}}_{ 4}^{ - } \), La(III), Ce(III) and Nd(III) along with Am(III) has been investigated with 1.1 M solutions of TiAP and TBP in n-alkane diluents from nitric acid medium. The extraction of Zr(IV) has been evaluated with unirradiated and gamma irradiated solvents as a function of organic phase uranium(VI) loading. The influence of degradation products of TiAP and TBP on the extraction behaviour of fission products has also been examined. The effect of diluent degradation products and effect of alkali wash on the extraction of Zr(IV) is discussed. The formation of interfacial deposits during the washing of gamma irradiated solvents with alkali solution is also discussed.

Classification and extraction methods of the clog components of constructed wetland

In order to quantitatively analyze the clog problem of constructed wetland (CW), it is necessary to establish appropriate classification and extraction methods of clog components. This study was intended to use five kinds of substances, which were proteins, polysaccharides, humic acids, nucleic acids and inorganic substances, to describe CW clog quantitatively. These substances accounted for about 71% of the total mass of the clog. The method is proved to be feasible and could provide quantitative analysis for study on the mechanism of clog. In CW clog, the proportion of proteins, polysaccharides, humic acids, nucleic acids and inorganic substances was 9.86%, 1.90%, 5.68%, 3.95%, 49.87%, respectively. The best way to extract components from the CW clog is to use the method of “alkali wash+hot alkali+low-speed centrifugal” (AKAKL). Due to its simplicity and feasibility, the method could be performed in each common laboratory and more importantly, it is controllable with low cost and strong anti-interference.

Enhanced Coagulation for Slightly Polluted Seawater Using Ferric Sulfate and Modified Diatomite

The modified diatomite was prepared by calcination and alkali washing, and the feasibility of using modified diatomite for enhanced coagulation treatment of slightly polluted seawater was investigated in this study. SEM and BET analysis showed that the raw diatomite contained impurities, which were removed after refined and purified treatment. The use of diatomite as a coagulant aid improved interparticle bridging thus incorporating the cells into flocs more efficiently, producing settleable flocs of greater density, size and strength. The enhanced coagulation with ferric sulfate and modified diatomite improved the removal efficiency of turbidity, ammonia nitrogen, total phosphorus and CODMn in seawater samples. At the optimal diatomite dosage of 60 mg/L and ferric sulfate dosage of 6 mg/L, the removal efficiency of turbidity, NH3-N, TP and CODMn reached 93.8%, 26.3%, 94.8% and 44.4% respectively. It has been proved that the enhanced coagulation through the ferric sulfate and modified diatomite, as coagulant aid and adsorbent, is more efficient and environmentally than using traditional metal coagulant only for treatment of slightly polluted seawater.

Purification of Byproduct Sodium Chloride from Dibenzoyl Methane Process by Alkali Washing

Purification of Byproduct Sodium Chloride from Dibenzoyl Methane Process by Alkali Washing

Kinetics of enzyme-catalyzed hydrolysis of steam-exploded sugarcane bagasse

This work presents the experimental kinetic data and the fractal modeling of sugarcane bagasse steam treatment and enzymatic hydrolysis. Sugarcane bagasse (50 wt% moisture) was pretreated by autohydrolysis at 210 °C for 4 min. Acid catalysis involved the use of 9.5mg g(-1) of H2SO4 or H3PO4 in relation to the substrate dry mass at these same pretreatment conditions. Unwashed, water-washed and alkali-washed substrates were hydrolyzed at 2.0 wt% using 8 and 15 FPU g(-1) (108.22 and 199.54 mg/g) total solids of a Celluclast 1.5 L and Novozym 188 mixture (Novozymes). The fractal kinetic modeling was used to describe the effect of pretreatment and both washing processes on substrate accessibility. Water and/or alkali washing was not strictly necessary to achieve high hydrolysis efficiencies. Also, the fractal model coefficients revealed that H3PO4 was a better pretreatment catalyst under the experimental conditions used in this study, resulting in the most susceptible substrates for enzymatic hydrolysis.