Dilute Acid Solution Research Articles

Elemental Analysis of Dietary Supplements by Microwave-Induced Plasma–Optical Emission Spectrometry (MIP-OES) With Ultrasound-Assisted Extraction (UAE)

The purpose of this study was to demonstrate the feasibility of determining metals (Cr, Mn, Zn, Fe, and Cu) in commercial dietary supplements using microwave-induced plasma optical emission spectrometry (MIP OES) after fast ultrasound-assisted extraction. Various parameters affecting the extraction process, such as the nature and concentration of the extractant solution, sonication time, and sample mass, were evaluated. Under the optimal conditions, it was possible to quantitatively extract metals from the samples by sonicating 1.0 g of the supplement dispersed throughout 25 mL of a 1.0 mol L−1 HNO3 for only 5 min. The developed method was applied to determine the analytes in four dietary supplements available in the Brazilian market. The results obtained with the extraction method were compared with the values obtained when the samples were completely mineralized with concentrated HNO3 in a microwave oven. There were no statistical differences between the developed and reference methods when the paired Student’s t-test was applied with a 95% confidence level. The application of ultrasound-assisted extraction was demonstrated to be advantageous compared to total sample digestion. This approach allowed the use of a higher mass of the sample, thereby enhancing the analytical capability of the method. Furthermore, employing less severe conditions, such as lower energy and a diluted acid solution, simplified and reduced the cost of the procedure compared to mineralization.

Inhibiting general and pitting corrosion of Ni in dilute sulfuric acid solutions with some tetrazole derivatives

5-(Benzylthio)− 1H-tetrazole (BST), ethyl-1H-tetrazole-5-acetate (ETA), and 5-(ethylthio)− 1H-tetrazole (EST) were utilized to inhibit the pitting and general corrosion of nickel in dilute sulfuric acid solutions. The galvanostatic anodic polarization under a constant current and mass loss measurement complemented by a scanning electron microscope is utilized. The tetrazole inhibitors retard the pitting corrosion by shifting the pitting potential, Ep into the more noble direction while lowering the amount of electricity, Qinh, needed to attain Ep. The protection efficiency, η, increased with increasing the amount of tetrazole in the solution to follow the order EST < ETA < BST. The protection influence of such inhibitors is accompanied by the blocking of the investigated metal surface by their molecules through an adsorption process that follows Langmuir's model. The computed -∆G⸰ads values are 37.17, 36.82, and 36.57 kJ/mol for BST, ETA, and ETA, successively, at 298 K. Such values are harmonious with a mixed chemo-, physisorption mechanism. A coordinate link is supposed to originate between the tetrazole compound and the investigated nickel surface.

Aspirin Spectrophotometric Determination using Cloud Point Extraction and HPLC in Several Pharmaceuticals Sold in Iraqi Markets

In this work, a sensitive tandem cloud-point extraction (CPE) method with a solvation system was employed to detect aspirin in various pharmaceuticals. Aspirin, in a dilute acidic solution, formed a complex with Zn(II) ions ([Zn(II)-aspirin] complex), which was then extracted using two different surfactant systems - nonionic surfactant Triton X-100 and a mixture of surfactants (SDS-Tween 80). The extracted complex was subsequently determined using spectrophotometry at a wavelength of 293 nm for Triton X-100 and 231 nm for SDS-Tween 80. The parameters for extraction, including HCl and Zn(II) concentration, temperature, heating time, and solvent used to dissolve the cloud point layer, were thoroughly investigated. Highperformance liquid chromatography (HPLC) was used as the standard method to compare the quantitative analysis of the cloud-point extraction-onium system.

Tracking the surface structure and the influence of cations and anions on the double-layer region of a Au(111) electrode.

We examined the electric double-layer (EDL) of a Au(111) electrode in a dilute perchloric acid solution using a combination of capacitance measurements and in situ scanning tunnelling microscopy under electrochemical conditions (ECSTM). The "camel-shaped" capacitance curve of the EDL is studied with different cations and anions, including their impact on the potential of zero charge (PZC). We show that the ECSTM images of thermally reconstructed and of the potential-induced surface reconstruction of Au(111) in perchloric acid electrolyte resemble previous work in sulphuric acid, displaying a herringbone pattern for a thermally reconstructed surface. Once the reconstruction is lifted, the Au(111) forms islands with an average of 1 atomic step height. When the potential is lowered below that of the PZC, the potential-induced surface reconstruction results in a more disoriented pattern than the thermally reconstructed surface. ECSTM images at different potentials are correlated with the voltammogram to understand the time and potential dependence of the surface. This correlation has led to the development of a potential window technique that can be used to reveal the surface structure of Au(111) based on observing the changes in PZC in the voltammogram. This method provides an indirect approach to understanding the surface structure without always relying on ECSTM. From the voltammogram, we also observed that anions (SO42-, CH3SO3-, ClO4-, F-) interact more strongly with the Au(111) surface than the alkali cations. The cation capacitance peak shape does not depend strongly on the identity of the alkali metal cation (Li+, Na+, K+). However, the anion capacitance peak depends strongly on the anion identity. It suggests that some level of specific adsorption cannot be excluded, even for anions that are traditionally not considered to adsorb specifically (perchlorate, fluoride).

Behavior of boron contained in foil brazing filler metal and corrosion resistance in dilute sulfuric acid and sodium chloride aqueous solutions

Behavior of boron contained in foil brazing filler metal and corrosion resistance in dilute sulfuric acid and sodium chloride aqueous solutions

Diglycolamic acid for the mutual separation of lanthanides and actinides from dilute nitric acid solution: solvent extraction, dynamic light scattering, and spectroscopic investigations

N,N-Dialkyl diglycolamic acid (HDRDGA) ligand was explored for mutual separation of Eu(iii) and Am(iii) from dilute nitric acid solution and the coordination chemistry of the metal with ligand was reported.

Effects of preparation method on thermoelectric properties of poly(aniline‐co‐3,4‐ethylenedioxythiophene)/SWCNT composites

AbstractComposites of conducting polymer and single‐walled carbon nanotubes (SWCNTs) are attracting great attentions in harvesting low‐grade waste heat. Prefabricated SWCNTs film used as the working electrode was placed at the liquid interface between the inorganic phase (dilute sulfuric acid solution) and the organic phase consisting of dichloromethane (DCM), aniline (ANI), and 3,4‐ethylenedioxythiophene (EDOT), together with a platinum wire (the counter electrode) and a silver chloride (AgCl/Ag) electrode (the reference electrode), to perform electrochemical polymerization of ANI and EDOT at the liquid interface. Thermoelectric (TE) composites of poly(ANI‐co‐EDOT) and SWCNTs were produced. Compared with composites from ultrasonic mixing and coating methods, the 10 wt% SWCNTs‐composites in situ formed in electrochemical polymerization have the highest power factor (PF) of 41.56 ± 3.58 μW m−1 K−2, higher than the PF values of the composites formed by other two methods. The work indicates that the TE properties of ANI‐EDOT copolymer/SWCNT (poly[ANI‐co‐EDOT]/SWCNT) composites prepared by electrochemical polymerization were better than those of the composites obtained by physical mixing the electrochemically synthesized poly(ANI‐co‐EDOT) with SWCNTs. Moreover, SWCNTs treated with sodium dodecylbenzene sulfonate (SDBS) could further improve the TE properties of the composites.

Insight into a novel circulation system combined with coordination leaching and biosorption for Cu(II) efficient recycling from electroplating sludge

A novel circulation system combined with coordination leaching and biosorption process was successfully used for the direct recycling of Cu2+ from the electroplating sludge. Cu2+ was firstly efficiently leached out from the sludge by the choosing organic acid, and then it was selectively adsorbed onto a modified sorbent from the lixivium containing other co-ions including Zn2+, Ca2+, Fe3+, Cr3+, and Mg2+ under dynamic adsorption condition. The results of static leaching experiments and DFT calculations showed that citric acid showed the best leaching performance for Cu2+ among the studied organic acids and the traditional inorganic acid (HCl). To selective recovery of Cu2+ from the lixivium, ethylenediamine tetraacetic acid dianhydride (EDTAD) modified bagasse was prepared, and it had high adsorption capacity, selectivity, and good reusability toward Cu-citric acid complex. The adsorption isotherm for Cu matched with the Langmuir model with a maximum adsorption capacity of 52.2 mg/g. XPS and EXAFS analysis illustrated that the Cu-citric acid complex was broken by EDTA on the modified bagasse, and Cu2+ enriched on the sorbent while citric acid was released into the lixivium again. In the combined leaching and sorption circulation system, Cu2+ was simultaneously absorbed on the modified bagasse fixed bed column once it was leached out. Benefitting the recycling of citric acid and the continuous adsorbing of Cu of the circulation system, the leaching efficiency could be increased from 75.0 % to 92.4 %, even in the very dilute citric acid solutions (concentration of 0.01 mol/L). The combined methods could increase Cu recovery efficiency from the sludge at a low concentration of the leaching agent, which had great potential in the practical application.

Enhancing ozone catalytic decomposition through acid treatment of α-MnO2 for improved activity and humidity resistance

Post-etching method using dilute acid solutions is an effective technology to modulate the surface compositions of metal-oxide catalysts. Here the α-MnO2 catalyst treated with 0.1 mol/L nitric acid exhibits higher ozone decomposition activity at high relative humidity than the counterpart treated with acetic acid. Besides the increases in surface area and lattice dislocation, the improved activity can be due to relatively higher Mn valence on the surface and newly-formed Brønsted acid sites adjacent to oxygen vacancies. The remnant nitro species deposited on the catalyst by nitric acid treatment is ideal hydrophobic groups at ambient conditions. The decomposition route is also proposed based on the DRIFTS and DFT calculations: ozone is facile to adsorb on the oxygen vacancy, and the protonic H of Brønsted acid sites bonds to the terminal oxygen of ozone to accelerate its cleavage to O2, reducing the reaction energy barrier of O2 desorption.

Microwave-assisted synthesis of catechol-based functionalized adsorbents for selective adsorption of critical element germanium

The critical element germanium lacks efficient and economical recovery process to recover it from dilute sources such as coal fly ash. In the current study, a novel microwave-based synthesis method was used to functionalize polystyrenic bead with catechol (A-Cat), nitro-catechol (A-Cat-N), and pyrogallol (A-Py). The adsorbents were used to selectively adsorb Ge from dilute acidic solutions and were investigated for pH dependency, adsorption isotherm, adsorption kinetics, Ge selectivity, and regeneration of adsorbent. The functionalization was confirmed with FTIR, and the grafting yields of 50 %, 41.7 %, and 62 % were achieved for catechol, nitro-catechol, and pyrogallol functionalization, respectively. The Ge adsorption followed Langmuir isotherm with Langmuir adsorption capacities of 29.76 mg/g, 39.14 mg/g, and 37.13 mg/g, for A-Cat, A-Cat-N, and A-Py, respectively, at pH 3. The adsorbents were highly selective for Ge against other elements at pH 1–3, showing no adsorption for many competitive ions at pH 1–2. The A-Cat was more selective than A-Cat-N and A-Py. The adsorbents followed pseudo-second-order kinetics. The adsorbents were reusable for multiple cycles; however, A-Cat-N and A-Py lost capacity due to incomplete desorption in the first cycle. The adsorption mechanism was surface complexation of germnaium with catechol ligand resulting in high selectivity. Linear free energy relationship was used to correlate the apparent adsorption equilibrium with metal hydrolysis constants, and these LFERs can be used to predict the relative selectivity of different cations on A-Cat, A-Cat-N, and A-Py.

Study on the mechanism of ultrasonic enhanced removal of zinc and germanium from lead residue

Lead residue is the residue from the leaching process of zinc oxide dust containing germanium, which comprises a certain amount of valuable elements such as zinc and germanium. Conventional water washing treatment cannot effectively remove zinc and germanium from lead residue, resulting in a backlog of zinc and germanium in the system and raising production costs for enterprises. By using a dilute sulfuric acid solution and introducing ultrasonic waves for enhanced washing, the easily separated zinc and germanium are basically removed, while the residual zinc occurred as ZnS and germanium wrapped in lead sulfate are difficult to elute. The removal efficiency of zinc and germanium can reach 53.82% and 50.24%, respectively, which are 12.67% and 6.10% higher than conventional acid washing efficiency, and 31.10% and 22.51% higher than conventional water washing efficiency. During water washing, the hydrolysis of Zn2+ and Fe3+ results in low elution efficiency. While in pickling process, hydrolysis can be effectively inhibited. When use ultrasonic to enhance sulfuric acid washing, some ZnS dissolves, while the silica gel colloid that adsorbs germanium is destroyed, and germanium is released into the solution again, thus improving the removal efficiency of zinc and germanium. This article has reused more than half of the residual zinc and germanium in lead residue, and points out the direction for further reducing zinc and germanium residues in lead residue. It is of great significance for the comprehensive utilization of zinc and germanium resources.

Mercury selective hydrogelation of a pyridinyl substituted terpyridine ligand

We report the addition of aqueous solution of different divalent transition metal ions M2+ (M = Mn, Fe, Co, Ni, Cu, Zn, Cd, Hg) to a dilute acidic solution of 4′-(pyridin-2-yl)-2,2′:6′,2″-terpyridine (L). An irreversible, translucent, and thixotropic hydrogel was selectively produced in the case of Hg(II). FESEM and HR-TEM images of Hg(II)-hydrogel showed non-uniform, fibrous, and cross-linked gel morphology. Further, the hydrogel was treated with sodium salts of different anions (F−, I−, Br−, Cl−, SO42−, NO3−, HCO3−, SO32−) in water. The iodide ion showed unusual behavior by forming a yellow precipitate of the hydrogel with a plate-like structure, as observed from FESEM images. DFT study has also been conducted to understand the aggregation behavior in Hg(II) based hydrogel. We also synthesized the mercury complex HgCl2L and characterized it by 1H NMR, elemental analysis, and mass spectrometry.

Effect of acid/alkali treatment on the structure and catalytic performance of 3DOM CeCo0.7Mn0.3O3 catalyst.

In this work, Ce was used as the A-site element and three-dimensional ordered macroporous (3DOM) materials as the template to obtain 3DOM CeCo0.7Mn0.3O3 catalyst via excessive impregnation method. The catalyst was subjected to acid/alkali treatment with dilute nitric acid and sodium hydroxide solutions. The results revealed that the catalysts subjected to acid/alkali treatment exhibited better structural and catalytic activity characteristics than the bulk catalyst. Specifically, the specific surface area of the catalyst treated with acid increased from 34.86 to 60.67 m2·g-1, and the relative contents of Oads and Mn4+ species increased. Moreover, the T90% further decreased to 174 °C. As for the catalyst treated with alkali, it exhibited a rougher surface and a wider pore size distribution, producing more lattice defects which were favorable for reaction progress. The T90% was 183 °C, indicating that acid/alkali treatment both had a positive effect on the catalytic oxidation of toluene.

Effect of wet chemical etching on femtosecond laser fabricated surface microstructure of polycrystalline ZnS

In this paper, wet chemical etching is employed to treat femtosecond (fs) laser fabricated surface microstructure on zinc sulfide (ZnS) to improve its surface quality (surface roughness) and regulate its size (depth/width ratio). Dilute nitric acid (HNO3) solution is selected as the etchant. First, the surface morphology of microgrooves before and after etching is observed as a function of etching time. Surface microcracks are also observed. Then, under different etchant concentrations, the size evolution of the microgrooves is measured for different etching time. Finally, an explanation for the changes in surface quality and size caused by etching is provided.

Membrane phenomena in dilute electrolytes

The self-consistent description of membrane effects at the “pure water–dilute weak electrolyte” boundary is proposed. The approach is based on a modification of the well-known statistics of electrolytes, governed by ionic equilibrium taking in terms of dissociation constants: Kaq (ionic product of water) and Kd (dissociation constant in Oswald’s law for diluting weak electrolytes). The formalism makes it possible to treat membrane effects in electrolytes based on the description of contact phenomena near the interface between two conducting media. In particular, it is possible to relate the membrane characteristics of the “pure water–dilute acetic acid solution” contact with the dissociation constants Kaq and Kd.

Tailoring of Hydrogen Generation by Hydrolysis of Magnesium Hydride in Organic Acids Solutions and Development of Generator of the Pressurised H2 Based on this Process

Hydrolysis of light metals and hydrides can potentially be used for the generation of hydrogen on-board fuel cell vehicles, or, alternatively, for refilling their fuel tanks with H2 generated and pressurised without compressor on site, at near-ambient conditions. Implementation of this approach requires solution of several problems, including the possibility of controlling H2 release and avoiding thermal runaway. We have solved this problem by developing the apparatus for the controlled generation of pressurised H2 using hydrolysis of Mg or MgH2 in organic acid solutions. The development is based on the results of experimental studies of MgH2 hydrolysis in dilute aqueous solutions of acetic, citric, and oxalic acids. It was shown that the hydrogen yield approaches 100% with a fast hydrolysis rate when the molar ratio acid/MgH2 exceeds 0.9, 2.0, and 2.7 for the citric, oxalic, and acetic acids, respectively. In doing so, the pH of the reaction solutions after hydrolysis corresponds to 4.53, 2.11, and 4.28, accordingly, testifying to the buffer nature of the solutions “citric acid/magnesium citrate” and “acetic acid/magnesium acetate”. We also overview testing results of the developed apparatus where the process rate is effectively controlled by the control of the acid concentration in the hydrolysis reactor.

Ultrasound-Driven Defect Engineering in TiO2-x Nanotubes─Toward Highly Efficient Platinum Single Atom-Enhanced Photocatalytic Water Splitting.

Single-atom catalysts (SACs) have demonstrated superior catalytic activity and selectivity compared to nanoparticle catalysts due to their high reactivity and atom efficiency. However, stabilizing SACs within hosting substrates and their controllable loading preventing single atom clustering remain the key challenges in this field. Moreover, the direct comparison of (co-) catalytic effect of single atoms vs nanoparticles is still highly challenging. Here, we present a novel ultrasound-driven strategy for stabilizing Pt single-atomic sites over highly ordered TiO2 nanotubes. This controllable low-temperature defect engineering enables entrapment of platinum single atoms and controlling their content through the reaction time of consequent chemical impregnation. The novel methodology enables achieving nearly 50 times higher normalized hydrogen evolution compared to pristine titania nanotubes. Moreover, the developed procedure allows the decoration of titania also with ultrasmall nanoparticles through a longer impregnation time of the substrate in a very dilute hexachloroplatinic acid solution. The comparison shows a 10 times higher normalized hydrogen production of platinum single atoms compared to nanoparticles. The mechanistic study shows that the novel approach creates homogeneously distributed defects, such as oxygen vacancies and Ti3+ species, which effectively trap and stabilize Pt2+ and Pt4+ single atoms. The optimized platinum single-atom photocatalyst shows excellent performance of photocatalytic water splitting and hydrogen evolution under one sun solar-simulated light, with TOF values being one order of magnitude higher compared to those of traditional thermal reduction-based methods. The single-atom engineering based on the creation of ultrasound-triggered chemical traps provides a pathway for controllable assembling stable and highly active single-atomic site catalysts on metal oxide support layers.

Analytical Method Development and Validation of Ubrogepant and their Degradation Studies in Bulk and Pharmaceutical Dosage form by RP-HPLC

An accurate, rapid economical and straight forward, reliable new analytical method was developed and validated for the quantification of Ubrogepant and their degradation studies by using RP-HPLC.In the proposed method efficient chromatographic separation was achieved by using Ammonium aecetate buffer with pH adjusted to 5.0 with dilute Orthophosphoric acid solution and methanol (30:70 v/v) as a mobile phase with a flow of 1 ml/min and Water and Acetonitrile(30:70) is used as a diluent, the wave length was observed at 280 nm with isocratic mode at ambient temperature and run time was approximately 10 min and the retention time (Rt) of Ubrogepant was observed as 4.570 min. The method validated as per ICH guidelines. System suitability parameters were studied by injecting six standard solutions of Ubrogepant and results were well under acceptance criteria. Linearity study was administered between 25% to 150% levels, Regression coefficient value was observed as 0.999. LOD and LOQ were observed as 0.02 ug/ml and 0.2 ug/ml, respectively. Precision was found to be 0.54 for repeatability and 0.33 for intermediate precision. Recovery of the drug was found to be 100.86% indicates that the recovery is in the acceptable limit. Stress conditions of degradation in Acidic, Alkaline, Peroxide and Thermal were studied for Ubrogepant and validation results were found to be satisfactory and the proposed method was suitable for regular analysis and quality control of pharmaceutical preparations.

The physico-chemical properties and sorption potentials of snail shell particulates, chitin, chitosan, and oxalic acid modified chitosan from &lt;i&gt;achatina fulica&lt;/i&gt; shell

The purpose of the research was to compare the properties of snail shell particulate (SSP) and its derivatives to those of commercial chitosan (CC) as potential adsorbents. Chitin (CT) was synthesized by deproteinizing and demineralizing SSP with dilute sodium hydroxide (NaOH) and hydrochloric acid (HCl) solutions, respectively. Chitosan (CH) was prepared by partially deacetylating CT with concentrated NaOH. The extracted CH was modified with 10.00% (w/v) oxalic acid (CH&lt;sub&gt;ox&lt;/sub&gt;). Energy dispersive X-Ray (EDAX), Fourier transform infrared (FTIR), Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), and chromium adsorption were used to characterize the materials. FTIR spectra of CT and CH materials showed the presence alkyne, nitrile, primary and secondary amines/amides groups with 83.98% as the degree of deacetylation. The spectra of EDAX of CT and CH samples showcased predominant peaks, which correspond to calcium, oxygen, yttrium, and silver. SEM images showed tight, porous, and fractured surface for CT and CH materials unlike the snail shell and CC. BET surface area of the adsorbents were in the increasing order of CT&amp;lt;CC&amp;lt;CH&lt;sub&gt;ox&lt;/sub&gt;&amp;lt;SSP&amp;lt;CH. CH has a greater surface area of 362.32 m&lt;sup&gt;2&lt;/sup&gt;/g and a mesoporosity of 71.41%. However CH&lt;sub&gt;ox&lt;/sub&gt; with moisture content 1.52%, bulk density of 0.58 g/cm&lt;sup&gt;3&lt;/sup&gt;, ash content (AC) 0.47% and pH 10.24, has better advantage to be used as biosorbent compared to CC with moisture content 1.08%, bulk density of 0.49 g/cm&lt;sup&gt;3&lt;/sup&gt;, AC 0.87% and pH 8.58. CH&lt;sub&gt;ox&lt;/sub&gt; had a higher chromium adsorption of 80.4 mg/g at a concentration of 150 mg/L, while having a relatively smaller surface area of 325.38 m&lt;sup&gt;2&lt;/sup&gt;/g (68.36% mesoporosity). The potential removal techniques include ionic interaction between chromium ion and functional groups and surface adsorption due to the textural characteristics of adsorbent samples. When compared to CC, snail shell particle and its derivatives are potential good adsorbents.

Changes in solubility and chemical speciation of potassium, calcium, and silicon in wood ash by acid treatment

ABSTRACT This study investigated the relationship between the solubility and the chemical speciation of plant nutritional elements (K, Ca, and Si) in wood ash treated with a dilute solution of sulfuric acid or phosphoric acid. The diluted acid solutions were added to fly ash (FA) collected from a power plant, and the untreated and acid-treated FAs were analyzed for their contents of K, Ca, and Si. The crystalline phases of the untreated and acid-treated FAs were identified using X-ray diffraction (XRD), and the Si species were determined using X-ray absorption near-edge structure (XANES) spectroscopy. Sulfuric acid and phosphoric acid treatments did not affect the solubility of K in FA. Water soluble and citrate soluble K in FA were decreased by the addition of these acids. The water soluble Ca content in FA treated with phosphoric acid did not show a significant change compared to that in the untreated FA, but it increased up to 65 times in FA treated with sulfuric acid. It is suggested that CaCO3, which was the main Ca species in the untreated FA, was transformed into syngenite and gypsum by the sulfuric acid treatment. Hydrochloric acid soluble Si in the acid-treated FA decreased compared to that in the untreated FA. In contrast, the NaOH-soluble Si fraction, a method for selectively extracting silica gel, increased especially in the phosphoric acid-treated FA. The results of XANES analysis showed that the FA samples treated with 10–30% sulfuric acid or 10–30% phosphoric acid had a lower degree of Si polymerization than the untreated FA, which corresponded generally to the increased Si solubility in FAs. However, FA treated with 30% sulfuric acid had lower soluble Si despite a lower degree of polymerization than FA, which was attributed to a lower pH. These results suggest that the change in solubility of Si in the acid-treated FA was influenced by the degree of polymerization and the decrease in pH. From the viewpoint of a fertilizer use of FA, sulfuric acid-treated ash, which consists of both water soluble Ca and citrate soluble Ca, is suitable for Ca fertilizer, and phosphoric acid-treated ash, which has high NaOH-soluble Si, is suitable for Si fertilizer