Acid Treatment Process Research Articles

Acid Treatment of Aluminium Dross: Properties and Application

This research work aimed to apply the aluminium dross, waste of ADC12 and 6063 aluminium smelter grade as the raw materials produced plant fertilizer by acid treatment process with phosphoric and hydrochloric acid. Chemical properties have been tested as a chemical composition, pH, amount of macronutriants and heavy metals. The germination index testing was confirmed by using water extraction of the dross before and after pretreatment which effected on cantonese green lettuce seed. The results showed that more than 50% by weight of dross composition was alumina mainly. Others components were included oxides of silicon, magnesium, sodium, potassium, calcium, iron, and zinc. Interestingly, there are not appeared of harmful heavy metal elements. For fertilization properties, mainly nutrients as nitrogen (N), phosphorus (P), and potassium (K) were investigated. Also, the germination test was investigated in an organic fertilizer standard test method as germination index (GI). Normally, the result was found that GI of un-treated dross was lower than that of a control sample. The treated dross with HCl and phosphoric acid presented higher GI than that of a reference sample. It was concluded that both grades of dross can be used as a fertilizer with acid treatment.

Synthesis and characterization of silica nanoparticles from clay

We report a method to synthesize silica nanoparticles from bentonite clay. A series of thermal and acid treatment processes was performed on bentonite clay to lower the alumina and increase the silica content. The obtained silica rich clay was treated in two different concentrations (10 wt% and 40 wt%) with sodium hydroxide solution to form sodium silicate solutions (SSS). One type of SSS was hydrolyzed with three different concentrations (5 M, 10 M and 15 M) of nitric acid in the presence of ethanol as cosolvent while the other SSS was hydrolyzed with nitric acid in the presence of three different quantities (10 ml, 20 ml and 30 ml) of ethanol as cosolvent. A range of silica particle sizes from nanometer to micrometer was obtained by varying the contents of silica rich clay, HNO3, and ethanol. It was observed that the concentration of silica rich clay and HNO3 had a direct effect on the particle size. The increase in the quantity of ethanol from 10 ml to 20 ml produced bimodal particles of nanometer and micrometer size, which maintained at 30 ml. Inductively coupled plasma optical emission spectroscopy, atomic absorption spectroscopy, X-ray fluorescence, scanning electron microscopy and X-ray diffraction were utilized to characterize the clay, SSS and nanoparticles.

Optical, morphology and electrical properties of In2O3 incorporating acid-treated single-walled carbon nanotubes based DSSC

This study focuses on the influence of an acid treatment process of single-walled carbon nanotubes (SWCNTs) in In2O3-based dye-sensitized solar cells (DSSCs). Pure In2O3, In2O3-SWCNTs with acid treatment and In2O3-SWCNTs without acid treatment were prepared using the sol–gel method via a spin coating technique annealed at 450 °C. The optical, morphology and electrical properties of the photoanodes were characterized by means of UV–Vis analysis, atomic force microscopy and field-emission scanning electron microscopy, and J–V curve measurements, respectively. The optical band gap obtained through UV–Vis analysis showed that the acid treatment process modified the band gap of the photoanode, which enhances the Voc of the DSSCs. In addition, In2O3-SWCNTs with acid treatment possess a porous structure that improves the power conversion efficiency (PCE) of the DSSCs. In addition, the diameter of acid-treated SWCNTs was reduced compared to pristine SWCNTs. In2O3-SWCNTs with acid treatment exhibited the highest PCE of 1.40% with Jsc of 7.6 mA cm−2, Voc of 0.51 V, and fill factor of 0.36. The increment in Voc is due to the higher band gap obtained through the UV–Vis absorption spectrum. Moreover, In2O3-SWCNTs with acid treatment has a higher electron lifetime with a higher effective diffusion coefficient that slows down the recombination rate and speeds up the electron transport process.

Advances towards a Clean Hydrometallurgical Process for Chromite

Because of the acute toxicity of Cr(VI)-bearing substances, the pollution problem caused by chromite process residue has become a worldwide concern. In the view of relevant studies, the technologies based on the alkali treatment cannot fundamentally resolve the pollution problem, because the oxidation of Cr(III) to Cr(VI) is unavoidable during chromite decomposition. In contrast, the oxidation of Cr(III) to Cr(VI) can be controlled by the sulfuric acid treatment of chromite, and the Cr(VI) pollution can be eliminated from the original source of production. Many research studies focusing on the resolutions of the key obstacles hindering the development of the sulfuric acid treatment process have been carried out, and significant progress has been achieved. In this study, a clean hydrometallurgical process without the generation of hexavalent chromium is demonstrated. First, the chromite was decomposed and leached by sulfuric acid solution in the presence of an oxidant. Then, iron was hydrothermally removed from the acid solution as the precipitate of jarosite. Finally, chromium salts were obtained by adjusting the basicity of the solution, separation and drying. With the aim of realizing industrialization, future research emphasis on the development of the sulfuric acid treatment process is proposed in this study.

The Effect of the Firing Conditions on the Properties of Barium Strontium Titanate Powders Prepared by Sol-Gel Combustion Method Using Citric Acid as Fuel

Barium strontium titanate (Ba0.7Sr0.3TiO3; BST) powders were prepared via sol-gel combustion method using citric acid as fuel. The molar ratio of sol powder: fuel = 1:1. All of the samples were calcined at 450–950°C for 2, 3 and 4 hours. The crystallinity of the powders was improved by increasing the calcination temperature indicated by the increasing of the perovskite peak intensity from the X-rays diffraction analysis. The pure perovskite phases were crystalline at temperature 750°C with calcination time 2, 3 and 4 hours, after that BST powders were applied with acid treatment process. The XRD result showed that the pure perovskite phase without the phase of pyrochlore in all of the samples.BST is in cubic structure, corresponding to JCPDS 34–0411. The morphology and microstructure of synthesized BST powders were analyzed by a scanning electron microscope (SEM). The particles were agglomerated, spherical shape and were larger corresponding with the increasing of calcination temperature and dwelling time. The average of particle size was about 50–115 nm.

Tailored Degree of Functionalization and Length Preservation of Multiwalled Carbon Nanotubes by an Optimized Acid Treatment Process

The introduction of oxygen groups in carbon nanotubes is considered crucial for many applications. However, there is a lack of controlled functionalization methods which ensure nanotubes with specific property values according to each interest. In this work, acid treatments of multiwalled carbon nanotubes (MWCNTs) employing an optimized ultrasound process with moderate heating and stirring were studied by means of a factorial design. The functionalized nanotubes were characterized by thermogravimetry, elemental analysis, Raman spectroscopy, electron microscopy and water stability tests. Statistic models were fitted for the degree of functionalization and length reduction of MWCNTs. Temperature was identified as a key parameter to produce more functionalized MWCNTs with less structural damage. The properties of the functionalized MWCNTs can be tailored by the choice of parameters exploited in the statistical models developed to enable different end-use requests, such as for polymeric composites or bio-related applications, which is the original contribution of this work.

Integrated utilization of algal biomass and corn stover for biofuel production

This paper describes a novel route for the utilization of algal and lignocellulosic biomass for biofuel production. Dilute sulfuric acid treatment was employed to destroy the rigid algal cells and generate algal hydrolysate. Algal hydrolysate was used as the reaction medium for the enzymatic hydrolysis of lignocellulose from corn stover. The acid treatment parameters were optimized based on the enzymatic efficiency of corn stover digestion and the promotion mechanism is discussed. The algal residues from the acid treatment process were co-digested with corn stover to generate methane. This study showed that algal hydrolysate can be used as a supplemental feedstock and reaction medium to enhance ethanol production. Furthermore, the residues could be utilized as the nitrogen source during the anaerobic digestion of corn stover.

Hydrometallurgical Recovery of Precious Metals and Removal of Hazardous Metals Using Persimmon Tannin and Persimmon Wastes

Novel and environmentally benign adsorbents were prepared via a simple sulfuric acid treatment process using the wastes of astringent persimmon, a type of biomass waste, along with persimmon tannin extract which is currently employed for the tanning of leather and as natural dyes and paints. The effectiveness of these new biosorbents was exemplified with regards to hydrometallurgical and environmental engineering applications for the adsorptive removal of uranium and thorium from rare earths, cesium from other alkaline metals such as sodium, hexa-valent chromium from zinc as well as adsorptive recovery of gold from chloride media. Furthermore, reductive coagulation of gold from chloride media for the direct recovery of metallic gold and adsorptive recovery of palladium and platinum using chemically modified persimmon tannin extract were studied. OPEN

Influence of the surface oxygenated groups of activated carbon on preparation of a nano Cu/AC catalyst and heterogeneous catalysis in the oxidative carbonylation of methanol

Coconut shell activated carbon (AC) is treated by nitric acid and used as a support to prepare nano-copper heterogeneous catalysts for oxidative carbonylation of methanol to dimethyl carbonate. AC supports and their corresponding catalysts are characterized intensively by BET, XPS, XRD, TEM, N2O chemisorption, CO adsorption, and TPR. The results show that the concentrations of nitric acid do not significantly changes the specific surface area and textural property of AC. But the oxygenated groups which result in acidic properties, such as lactone, carboxyl and phenol groups, are formed on AC surface during the acid treatment process and increase with the increasing concentration of nitric acid. The increased surface oxygenated groups not only influence the dispersion but also the valence distributions of copper species. When copper supported on the AC treated by 4M HNO3, the Cu/AC catalyst shows the optimal catalytic performance for oxidative carbonylation of methanol to dimethyl carbonate, which might be ascribed to the highest dispersion of Cu+ and Cu0 species. The average conversion of methanol and space-time yield of DMC (STYDMC) within 10h for the catalyst have reached 9.2% and 229mgg−1h−1, respectively. The deactivation of Cu/AC catalysts is attributed to the agglomeration of copper species. Besides, the STYDMC of per S(Cu++Cu0) for the acid treated Cu/AC catalysts is very similar and less than that of the original Cu/AC catalyst which may be induced by the AC surface oxygenated groups itself but not the ratio of Cu+/Cu0.

Direct use of as-synthesized multi-walled carbon nanotubes for carbon dioxide reforming of methane for producing synthesis gas

Abstract In this study, laboratory prepared multi-walled carbon nanotubes (MWCNTs) over Co–Mo/MgO catalysts were used as novel nanocomposite catalysts for carbon dioxide reforming of methane (CRM). The influence of acid treatment process on the catalyst performance was thoroughly investigated. It was determined that Co–Mo/MgO present in the as-synthesized MWCNTs was responsible for high catalytic activity of the reforming reaction. The performance of the nanocomposite catalysts was compared with the conventional Co–Mo/MgO catalysts prepared by sol–gel method, revealing that MWCNTs played a supporting role in preventing catalyst deactivation. The nanocomposite catalysts gave CH 4 and CO 2 conversions of 97% and 98% , respectively, for the CRM reactions performed at 850 °C with a GHSV of 120 L/h g cat and a CH 4 /CO 2 ratio of 1 under atmospheric pressure. Stability tests, carbon deposition and characteristics of the nanocomposite catalysts were investigated up to 100 h of reaction. The proposed reaction mechanism for this catalyst shows that CH 4 decomposition and carbon gasification by CO 2 were the two important side-reactions.

INTERACTION OF WATER-DISPERSIBLE, LIGAND-FREE NaYF4:Yb/Er UPCONVERSION NANOPARTICLES WITH BOVINE SERUM ALBUMIN

The oleate capped NaYF 4: Yb / Er upconversion nanoparticles (OA-UCNPs) were firstly synthesized by the thermal decomposition method and subsequently converted to water-dispersible, ligand-free UCNPs (LF-UCNPs) via an easy acid treatment process. The interaction of LF-UCNPs with bovine serum albumin (BSA) was then investigated. The binding of LF-UCNPs with BSA was confirmed by the static quenching of intrinsic fluorescence of BSA upon addition of LF-UCNPs. The spectra of synchronous fluorescence and circular dichroism (CD) of BSA in the absence and presence of LF-UCNPs revealed that the presence of LF-UCNPs led to a slight conformational change of BSA, suggesting a minor nanotoxicity of LF-UCNPs toward BSA.

Characterisation and surface chemical modification of starch nanoparticles with lactid through ring opening polymerisation

Waxy corn starch nanoparticles were prepared by an acid treatment process. The obtained starch nanoparticles were modified by ring opening polymerisation of lactide and the structure of the resulted polymers characterised with Fourier transform infrared (FTIR) spectroscopy. Weight fraction of starch nanoparticles and modified starch calculated by elemental analysis experiment. Thermal characteristic of the modified starch nanoparticles was investigated using thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques. By surface chemical modification of starch nanoparticles, the thermal properties of modified starch nanoparticles have improved and starch nanoparticles showed greater thermal stability. Also wettability tests showed that the surface characters of starch nanoparticles have been changed during modification and modified starch nanoparticles have higher affinity toward organic solvents rather than aqueous media. X-ray diffraction studies showed that the starch crystalline structure has not changed during the reaction.

Synthesis and Properties of Lithium Ion-sieve Precursor Li4Mn5O12

Adsorption method is the most promising method for extraction of lithium from salt lakes. A new kind of MnO2 ion-sieves with high Li + selective adsorption property were synthesized. Spinel-type Li4Mn5O12 precursors were synthesized by EDTA-citrate complexing method using LiNO3 and Mn(NO3)2·4H2O as starting materials. MnO2 ion-sieves with Li + selective adsorption property were prepared by the acid treatment process to extract Li + from the spinel Li4Mn5O12 precursors. As-prepared samples were characterized by thermo gravimetric, XRD, SEM, FT-IR and Li + selective adsorption measurements, respectively. The results show that calcination time has a consid- erable effect on the structure and composition of precursors. The precursor calcined at 400℃ for 24 h has a pure phase of Li4Mn5O12. Final MnO2 ion-sieve and Li4Mn5O12 precursor are about 200 nm spherical pellets and have the same structure of spinel. The maximum adsorption capacity of ion-sieve is about 43.1 mg/g and has the good selec- tion for Li

Properties of Coal Tar Pitch Modified with Acid and Oxidation Treatment

To achieve lower price and high performance of pitch carbon fiber, coal tar pitch has to restructure through high-purity process, thermal and acid treatment process, and separation process. Thermal treatment and different oxidation treatments were used to increase the softening point and yield of the precursor pitch for carbon fiber. These treatments have the effect on the properties of carbon fiber because they cause considerable change in the chemical composition of pitches. Low molecular weight materials could be removed by the thermal treatment. The oxygen containing structure formed by the acid treatments would promote the poly-condensation and polymerization reactions. The oxidation treatment with sulfuric acid, nitric acid, and air blowing would lead to the remarkable change in the chemical composition of pitches, and resulted in considerable increase in the softening point and yield of the pitches.

Effect of the Fuel Type on the Synthesis of Barium Strontium Titanate by Sol-Gel Combustion Method

The ferroelectric ceramic, Barium Strontium Tinanate (Ba0.7Sr0.3TiO3), was prepared by the sol-gel combustion method using citric acid, urea, and glycine as the fuel for reduce the calcination temperature. The molar ratio of sol powderto fuel was 1:1. All of the samples were calcined at 450, 550, 650, 750, 850 and 950°C for 2 h. Then,Ba0.7Sr0.3TiO3powders were applied with acid treatment process. X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscope (TEM) analysis were used to characterize the crystal structure and microstructure. The perovskite phases of BST and the pyrochlore (BaCO3,SrCO3) were obtained after the calcinations temperature of 550°C. BST powders were applied with acid treatment process.The XRD result showed the pure perovskite phase without the phase of pyrochlore in all of the samples. Ba0.7Sr0.3TiO3was in cubic structure, corresponding to JCPDS 34-0411. SEM analysis of BST powders calcined at 750°C.The particles were spherical morphology and had agglomerates while the particles sizes were larger corresponding with the increase of calcinations temperature.The results for TEM analysis of the BST powders prepared by using urea as the fuel had a smaller particles,and the average of particle size was about 47 nm.

Melanin Bleaching With Dilute Hydrogen Peroxide

Melanins are naturally occurring pigments in both normal and pathologic tissues. Two common bleaching processes are potassium permanganate followed by oxalic acid treatment and dilute hydrogen peroxide (H2O2) process. The potassium permanganate/oxalic acid method is faster and more easily incorporated in conventional daily immunostaining protocols, whereas the dilute H2O2 method requires 24 hours. This study aimed to reduce melanin bleaching time by using a 10% H2O2 dilution. First, reaction time was reduced to 30 minutes by raising the temperature to 65°C. Second, containers with high thermal conductivity were used to improve bleaching effectiveness. Experimental comparisons of melanin treatments with H2O2 contained in an iron jar, a glass coplin jar, and a plastic steel jar obtained bleaching time of 20, 30, and 40 minutes, respectively. These modifications of the conventional bleaching method significantly improve the speed and efficiency of the procedure and are recommended when performing immunohistochemical studies.

The effects of acid leaching on porosity and surface functional groups of cocoa (Theobroma cacao)-shell based activated carbon

Cocoa shell pellets were converted into activated carbon (CSAC) by carbonization at 800°C followed by activation at 850°C in CO2 flow until reaching burn off at approximately 48%. The CSAC was treated with hydrochloric acid (HCl) using response surface methodology (RSM), where the effect of soaking times (1, 2 and 4h), temperatures (30, 50, 70°C) and concentration of HCl (0.1, 1 and 2M) were studied. CSAC treated with 1M HCl at higher temperatures (>60°C) yielded CSAC with low ash content (<10%). Acid-treatment process parameters, particularly the reaction temperature, determined the composition and types of functional groups existing in the CSAC. High concentrations of oxygen functional groups were detected in both untreated CSAC and CSAC treated at low acid concentration (1M). High concentrations of nitrogen functional groups were detected only in CSAC treated at acid concentration (2M).

Post-synthesis, characterization and catalytic properties of fluorine-planted MWW-type titanosilicate

F-Ti-MWW was post-synthesized by implanting fluorine species into a Ti-MWW framework through an acid treatment process in the presence of ammonium fluoride. The effects of NH4F addition amount, acid treatment temperature and precursor Ti content were investigated on the incorporation of F species, the zeolite structure and the coordination sites of Ti. Fluorine-implanting improved the surface hydrophobicity of the zeolite and altered the electropositivity nearby the tetrahedral Ti sites through forming the SiO3/2F and SiO4/2F(-) units. The negative effect of SiO4/2F(-) units in F-Ti-MWW was eliminated selectively by convenient anion-exchange with various alkali chlorides. F-Ti-MWW containing the SiO3/2F units possessed better catalytic activity and reusability, and a longer catalyst lifetime than conventional Ti-MWW.

Study of Changes to the Organic Functional Groups of a High Volatile Bituminous Coal during Organic Acid Treatment Process by FTIR Spectroscopy

A high volatile bituminous coal was subjected to a series of organic acid treatment in steps using citric acid (1 hr and 2 hr) and buffered EDTA with acetic acid (1 to 3 hr) at room temperature. Leaching was performed with acetic acid (2N) also for 1 hr. Citric acid procedure reduced the mineral matter below 1.94%. Calcites and aluminates are completely removed along with substantial quantity of silicates by citric acid leaching. The change in absorption of organic functional groups and mineral matter in coal samples were studied using Fourier transform infrared spectroscopy (FTIR). Analysis indicated that oxygen containing species were decreased in the coal structure during acetic acid and citric acid (40%) procedure and buffered EDTA 3 hours leaching. As the period of leaching with buffered EDTA increased from 1 hr to 3 hr, organic functional groups and mineral functional groups decreased its intensity. The results indicated that the described acid treatment procedures with citric acid have measurable effects on the coal structure.

Preparation of char from lotus seed biomass and the exploration of its dye removal capacity through batch and column adsorption studies

Char was obtained from lotus seed biomass by a simple single-step acid treatment process. It was used as an adsorbent for the removal of malachite green dye (MG) from simulated dye bath effluent. The adsorbent was characterized for its surface morphology, surface functionalities, and zero point charge. Batch studies were carried out by varying the parameters such as initial aqueous pH, adsorbent dosage, adsorbent particle size, and initial adsorbate concentration. Langmuir and Freundlich isotherms were used to test the isotherm data and the Freundlich isotherm best fitted the data. Thermodynamic studies were carried out and the thermodynamic parameters such as ∆G, ∆H, and ∆S were evaluated. Adsorption kinetics was carried out and the data were tested with pseudofirst-order model, pseudosecond-order model, and intraparticle diffusion model. Adsorption of MG was not solely by intraparticle diffusion but film diffusion also played a major role. Continuous column experiments were also conducted using microcolumn and the spent adsorbent was regenerated using ethanol and was repeatedly used for three cycles in the column to determine the reusability of the regenerated adsorbent. The column data were modeled with the modeling equations such as Adam-Bohart model, Bed Depth Service Time (BDST) model, and Yoon-Nelson model for all the three cycles.