Effect Of Sulfuric Acid Concentration Research Articles

Optimization of Ultrasonic Assisted Saccharification of Sweet Lime Peel for Bioethanol Production Using Box–Behnken Method

In this study, ultrasonication was investigated for hydrolysis of sweet lime peel instead of utilizing it as a pretreatment process. Ultrasonication is one of the upcoming hydrolysis techniques that can offer high reducing sugar yield in shorter times and temperature with reduced acid consumption. Optimization studies of the hydrolysis process parameters were carried out to maximize the reducing sugar yield using the Box–Behnken method. From Box–Behnken design, 46 experiments were conducted and the effect of sulfuric acid concentration, peel concentration, sonication time, temperature and amplitude of ultrasound on reducing sugar yield were investigated. Fermentation of the hydrolysate was performed using baker’s yeast and the effect of time and pH on ethanol production was studied. Maximum ethanol yield by fermentation was observed as 64%. Scanning electron micrographs revealed that the regular and compact surface of raw biomass was altered into an irregular and scattered surface as a result of pretreatment and hydrolysis, which showed the prospective feasibility of sulfuric acid assisted steam explosion pretreatment and ultrasound assisted acid hydrolysis. From the experimental study, it was observed that ultrasonication can be explored for hydrolysis of pretreated lignocellulosic biomass to obtain high reducing sugar yield for bioethanol production.

Leaching of nickel from a secondary source by sulfuric acid

In the present study, leaching of tailing containing 29.6wt.% Ni in sulfuric acid was investigated. Tailing was characterized by X-ray powder diffraction (XRD), X-ray fluorescence (XRF) and inductively coupled plasma (ICP-OES) methods. Rinsing process for the separation of tungsten from tailing was conducted in distilled water at 80°C for 240min. After the filtration of solid residue from tungsten solution by vacuum filtration, batch leaching tests were carried out on solid residue at atmospheric pressure in stirred acid solution. The effects of sulfuric acid concentration (1–4mol), pulp density (1/10–1/20gmL−1), particle size (−600+420 to −180+125mm) and temperature (25–80°C) on the nickel dissolution were studied. The results showed that leaching of about 99% of nickel content of the washed tailing could be achieved using 4.0mol sulfuric acid, pulp density of 1/20gmL−1 and particle size of −180+250mm at 80°C after 240min. Kinetic analysis of the leaching data properly followed the shrinking core model, and the dissolution rate of nickel was found to be controlled by diffusion through the product layer for 25 and 40°C and chemical reaction for 80°C. Leaching rate of nickel at 60°C at the first stage (0–60min) was controlled by diffusion through the product; then, at the second stage, it was controlled by the chemical reaction (60–240min).

Combined acid/alkaline-peroxide pretreatment of olive tree biomass for bioethanol production

Olive tree biomass (OTB) can be used for producing second generation bioethanol. In this work, extracted OTB was subjected to fractionation using a sequential acid/alkaline oxidative pretreatment. In the first acid stage, the effects of sulfuric acid concentration and reaction times at 130°C were investigated. Up to 71% solubilization of hemicellulosic sugars was achieved under optimized conditions (2.4% H2SO4, 84min). In the second stage, the influence of hydrogen peroxide concentration and process time were evaluated at 80°C. Approximately 80% delignification was achieved under the best operational conditions (7% H2O2, 90min) within the experimental range studied. This pretreatment produced a substrate with 72% cellulose that was highly accessible to enzymatic attack, yielding 82g glucose/100g glucose in delignified OTB.Ethanol production from both hemicellulosic sugars solubilized in the acid pretreatment and glucose from enzymatic hydrolysis of delignified OTB yielded 15g ethanol/100g OTB.

Recovery of Cobalt and Lithium from Spent Lithium Ion Batteries

In this research a combination of mechanical separation, reductive leaching and chemical precipitation are used to regain Li as Li2CO3 and Co as Co(OH)2 from waste lithium ion batteries. First batteries are dismantled and different component are separated. Anode and cathode foils are grinded and sieved to extract Al and Cu from spent battery powder. The separation efficiency for copper and aluminum are 97.68% and 84.41% respectively. The separated powder is leached with sulfuric acid and hydrogen peroxide solution to dissolve cobalt and lithium. The effects of sulfuric acid concentration, time, temperature, concentration of hydrogen peroxide and S/L on the leaching efficiency for cobalt and lithium are studied. Design of experiments by Taguchi method is used to determine experiments conditions, analysis the results, and identify the optimum leaching conditions. The optimum leaching conditions are 1.5 M acid concentration, 60 minute, 60 °C, 15% H2O2, and 40 g/l solid to liquid ratio. Leaching efficiencies of 94.07% Co and 98.15% Li are achieved with these optimum conditions. Leaching solution of the optimum experiment is used to recover cobalt as cobalt hydroxide and lithium as lithium carbonate by chemical precipitation. An equivalent volume of 4M NaOH is used to precipitate cobalt as cobalt hydroxide. After 1 hour 99.98%, Co is precipitated and collected by filtration and dried. After collection of the Co(OH)2 product, the remaining solution is treated with equivalent volume of "saturated solution" of Na2CO3 at 100 °C to recover lithium as Li2CO3. After 1 hour, 80 – 85 % Li is precipitated, filtrated and dried. Precipitation products are investigated with XRD, which confirmed that cobalt hydroxide and lithium carbonate are recovered from leaching solution.

Influence of microwaves on the leaching kinetics of uraninite from a low grade ore in dilute sulfuric acid

This paper describes a study on microwave assisted leaching of uranium from a low-grade ore of Indian origin. The host rock for uranium mineralization is chlorite-biotite-muscovite-quartzo-feldspathic schist. The dominant presence of siliceous minerals determined leaching of uranium values in sulfuric acid medium under oxidizing conditions. Process parametric studies like the effect of sulfuric acid concentration (0.12–0.50M), redox potential (400–500mV), particle size (600–300μm) and temperature (35°–95°C) indicated that microwave assisted leaching is more efficient in terms of overall uranium dissolution, kinetics and provide relatively less impurities (Si, Al, Mg and Fe) in the leach liquor compared to conventional conductive leaching. The kinetics of leaching followed shrinking core model with product layer diffusion as controlling mechanism.

Effect of Sulfuric Acid Concentration on Electrochemical Characteristics of Nano Porous Structure Formed by Anodizing Process.

Aluminum alloy is a very strong reactivity material, but it has excellent corrosion resistance due to protective oxide film created in air. However, it is not practical because the film thickness is uneven and varies depending on the generation condition. Therefore, aluminum anodizing was performed to form film with commercially applicable hardness, corrosion resistance, and wear resistance. This offers such advantages as commercial applicability to large areas and low prices. In this study, the electrochemical characteristics with concentration of sulfuric acid electrolyte were compared with the two-step anodizing method which is widely used. A surface observation revealed regular structures and pores with the size of several tens of nm, and the anodized film presented excellent corrosion resistance with considerably low corrosion current density in sea water.

Preparation and Characterization of Microcrystalline Cellulose (MCC) by Acid Hydrolysis Using Microwave Assisted Method from Cotton Wool

SummaryThe microcrystalline cellulose (MCC) was extracted by microwave assisted from cotton wool. The effects of sulfuric acid concentration, time and temperature on the yield were investigated by a single factor experiments and the preparation condition were optimized using 23 factorial design and analyzed by statistical test. The obtained MCC were characterized using particle size analyzer, FT‐IR and XRD. The results showed that the main parameter in order of increasing effects on the MCC yield were time, temperature and acid concentration. The optimum condition was found at acid concentration 55% (w/w), time 1 minute and temperature 30°C. The range of particle size at that condition was from 0.052 μm to 353.078 μm, the yield was 78.67% (w/w) and the crystallinity index was 53.16%. Moreover the crystal structure transformed from cellulose I to cellulose II. The crystal structure of cellulose II was obtained without mercerization and ionic liquid treatments.

Microwave Assisted Energy Efficient Biodiesel Production from Crude Pongamia pinnata (L.) Oil Using Homogeneous Catalyst

Abstract Microwave assisted biodiesel production from crude Pongamia pinnata oil using homogeneous base catalyst (KOH) was unsuccessful because of considerable soap formation. Therefore, a two step process of biodiesel production from high free fatty acid (FFA) oil was investigated. In first step, crude P. pinnata oil was acid catalyzed using H 2 SO 4 and acid value of oil was reduced to less than 4 mg KOH/g. Effect of sulfuric acid concentration, alcohol-oil molar ratio and microwave irradiation time on acid value of oil was studied. Result suggested that 1.5% H 2 SO 4 (w/w), 6：1 methanol oil molar ratio and 3 min microwave irradiation time was sufficient to reduce the acid value of oil from 12 and 22 mg KOH/g to 2.9 and 3.9 mg/KOH/g, respectively. Oil obtained after pretreatment was subsequently used for microwave assisted alkali catalyzed transesterification. A higher biodiesel yield (99.0%) was achieved by adopting two step processes. Microwave energy efficiency during alkali catalyzed transesterification was also investigated. The results suggested a significant energy saving because of reduced reaction time under microwave heating.Key Words: microwave, pongamia pinnata, biodiesel, acid value, energy efficiency

Optimization of Preparation of Cellulose Nanocrystals from Peanut Shells Using Response Surface Methodology

The value of peanut shells as agricultural wastes can be increased by recycling and utilizing these waste shells for the production of nanomaterials. To achieve this purpose, this study prepared cellulose nanocrystals from peanut shells by sulfuric acid hydrolysis. The central composite design based on the response surface methodology was applied to study the effects of sulfuric acid concentration, reaction temperature and reaction time on the yield of cellulose nanocrystals and the regression model was established between the yield and three factors. The results showed that the yield of the cellulose nanocrystals was 44.94%, under the optimum conditions of 64.6% of sulfuric acid concentration, 49.5°C of reaction temperature and 28.5 min of reaction time. The morphology and crystallinity index of cellulose nanocrystals were examined by transmission electron microscopy and X-ray diffraction. Transmission electron microscopy showed that cellulose nanocrystals presented a rod-shaped nature with the diameter ranging from 5 to 25 nm. X-ray diffraction indicated that cellulose nanocrystals were the type of cellulose I pattern, with a crystallinity of 74.71%.

Separation of Heavy Bivalent Metals Extracted by Electrodeposition Using a STEEL Substrate from Wastewater

ABSTRACTHeavy metals contaminated waste water sludge is classified as hazardous solid waste(1). For this reason it needs to be properly treated to prevent releasing heavy metals to the environment.The sludge was treated in a batch reactor (2) by sulfuric acid to extract the contained heavy metals ( Cu; Cd; Ni and Zn).The effects of sulfuric acid concentration and solid to liquid ratio on the heavy metal removal efficiencies were investigated. The experimental results showed that the total and individual heavy metal removal efficiencies increased with increasing sulfuric acid concentration, but decreased with increasing solid to liquid ratio.For 5g/L solid to liquid ratio, more than 99,9% of heavy metals can be removed from the sludge by treating with 0,5 M sulfuric acid in 2h.The separation, of metals extracted by sulfuric acid from the sludge, is carried out by plating on steel substrate (3).The electrode position is performed in two different media: acid and basic media. A comparative study of the two plating media was studied.References;(1) B.Johnke, B.Wiebusch, Fuel Energy .38(1997)350(2) M.A.Styllanou,D.Kollia,K.J.Haralambous,V.J.Inglezakis,K.G.Moustakas,M.D.Loizidou, Desalination215(2007)73-81(3) Mortaga M.Abou-Krisha, Applied surface science 252(2005)1035-1048

Study on Sugar Production Conditions of Dilute Sulfuric Acid Hydrolysis of Corn Straw

In this paper, through the study of reducing sugar conditions of corn straw hydrolysis under acidic condition, looking for the production of experimental conditions relatively reasonable. Mainly by dilute sulfuric acid hydrolysis of corn straw by single factor test, effects of sulfuric acid concentration, temperature, reaction time, particle size, ratio of solid to liquid five factors, effects on sugar yield of corn straw. The dilute sulfuric acid concentration 5%, ratio of solid to liquid was 1:14, when the reaction time is 140 min, particle fineness of 120 mesh, the reaction temperature is 100 °C, corn stalk sugar yield reached a maximum 20.11%.

Kinetic Study and Mathematical Model of Hemimorphite Dissolution in Low Sulfuric Acid Solution at High Temperature

The dissolution kinetics of hemimorphite with low sulfuric acid solution was investigated at high temperature. The dissolution rate of zinc was obtained as a function of dissolution time under the experimental conditions where the effects of sulfuric acid concentration, temperature, and particle size were studied. The results showed that zinc extraction increased with an increase in temperature and sulfuric acid concentration and with a decrease in particle size. A mathematical model able to describe the process kinetics was developed from the shrinking core model, considering the change of the sulfuric acid concentration during dissolution. It was found that the dissolution process followed a shrinking core model with “ash” layer diffusion as the main rate-controlling step. This finding was supported with a linear relationship between the apparent rate constant and the reciprocal of squared particle radius. The reaction order with respect to sulfuric acid concentration was determined to be 0.7993. The apparent activation energy for the dissolution process was determined to be 44.9 kJ/mol in the temperature range of 373 K to 413 K (100 °C to 140 °C). Based on the shrinking core model, the following equation was established: $$ 1.21\ln \left( {1 - 0.83x} \right) - \left[ {1.02\ln \frac{{0.35 + \left( {1 - x} \right)^{{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-0pt} 3}}} - 0.59\left( {1 - x} \right)^{{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0pt} 3}}} }}{{0.35 + \left( {1 - x} \right)^{{{2 \mathord{\left/ {\vphantom {2 3}} \right. \kern-0pt} 3}}} + 1.18\left( {1 - x} \right)^{{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0pt} 3}}} }} + 3.52\arctan \left( {1.96\left( {1 - x} \right)^{{{1 \mathord{\left/ {\vphantom {1 3}} \right. \kern-0pt} 3}}} - 0.58} \right)} \right] + 2.06 = 42,192.59{\text{e}}^{{ - \frac{44,900}{{{\text{R}}T}}}} t. $$

Peculiarities of cellulose nanoparticles

The effects of sulfuric acid concentration and temperature have been studied to optimize the preparation of crystalline nanoparticles (CNP) and amorphous nanoparticles (ANP) of cellulose. To isolate CNP with increased yield (67%-70%) requires hydrolysis with warm 58-60 wt% sulfuric acid. CNP having average sizes of 150 × 15 nm and heightened yield can be obtained by using optimal hydrolysis conditions together with vigorous disintegration. Because of its highly crystalline structure, CNP have increased specific gravity and low hydrophility and accessibility. CNP potentially can be used as a nano-filler to improve properties of pastes, glues, paints, and coating compositions. To isolate ANP having an average diameter of 100 nm with the optimal yield (65-67%), cold 65-66 wt% sulfuric acid should be used in combination with vigorous disintegration. Because of their amorphous structure, ANP acquire such specific features as increased content of functional groups, high accessibility, enhanced sorption ability and hydrophility, and high viscosity and thickening ability. Given the specific features of ANP, their main application area might be for immobilization of biological active substances and drugs, filling and thickening of cosmetic and medicine remedies (e.g., pastes, creams, sprays, etc.).

DISSOLUTION AND PRECIPITATION OF ZINC AND MANGANESE OBTAINED FROM SPENT ZINC-CARBON AND ALKALINE BATTERY POWDER

The aim of this study was to investigate manganese and zinc recoveries from spent zinc-carbon and alkaline battery powder. The effect of sulfuric acid concentration, ascorbic acid dosage, reaction temperature and leaching time on zinc and manganese dissolutions was investigated. The optimum reductive acid leaching conditions were determined as: 3 hours, 70 °C, 0.5 M of sulfuric acid concentration, 13 g/dm 3 of ascorbic acid dosage, 1/20 g/cm 3 of solid/liquid ratio and 200 rpm of stirring speed. Under these conditions, dissolution efficiencies were 99.99% for Zn and 99.25% for Mn. In addition, dissolution kinetics of manganese was undertaken, and the activation energy was found to be 7.04 kJ/mol. Using 3 M NaOH as precipitating agent at room temperature, 95.35% of Zn (at pH 8) and 93.66% of Mn (at pH 10) were precipitated from the leaching solution. Under the same conditions, using 3 M KOH, precipitations of Zn and Mn were 91.63% and 96.39%, respectively. Based on the experimental results, a flowsheet of zinc and manganese recovery was proposed.

Environmentally friendly preparation of exfoliated graphite

Graphite intercalation compounds (GIC) have received global attention in the last decade because of the growing number of applications of these materials. Conventionally, bisulfate intercalated graphite is synthesized by chemical intercalation; which requires concentrated sulfuric acid (98%) and an oxidizing agent such as H2O2 and HNO3. In this study, bisulfate intercalated graphite was prepared by electrochemical intercalation using dilute sulfuric acid with the aim to reduce the sulfur content in the final product. The electrochemical intercalation method required sulfuric acid with half of the concentration of that required for chemical intercalation, and without the need for an oxidizing agent. Chinese natural large flake graphite was used as the raw material for the electrochemical process. The GIC was characterized by the exfoliation volume obtained by thermal shock at a temperature of 850°C. The effect of sulfuric acid concentration, electrochemical treatment time, particle size and temperature on the exfoliation volume was investigated. It was found that the exfoliation volume of the GIC-bisulfate, which is a function of degree of intercalation, can be controlled using the sulfuric acid concentration and treatment time. A sulfuric acid concentration of 50% and an electrochemical treatment time of 60min were found to produce a GIC with the maximum exfoliation volume for the range of conditions studied.

Acid leaching kinetics of zinc plant purification residue

The leaching processes of zinc plant purification residue in sulfuric acid solution were investigated with respect to the effects of sulfuric acid concentration, reaction temperature, and particle size. A particle size of 75–80 μm was required to leach 99.8% cobalt and 91.97% zinc at 70 °C for 20 min when the sulfuric acid concentration was 100 g/L and the ratio of liquid to solid was 50?1 (mL/g). The leaching kinetics of zinc plant purification residue in sulfuric acid solution system conformed well to the shrinking core model, and the dissolution rates of cobalt and zinc were found to be controlled by diffusion through a porous product layer. The apparent activation energy values of cobalt and zinc reaction were calculated to be 11.6931 kJ/mol and 6.6894 kJ/mol, respectively, according to the Arrhenius formula equation. The results show that diffusion through the inert particle pores is the leaching kinetics rate-controlling step.

Study on enzymatic saccharification of Suaeda salsa as a new potential feedstock for bio-ethanol production

Suaeda salsa, a herbaceous species widely distributed in Chinese seaside and desert, not only regulates soil environment, but also provides considerable amounts of biomass. In this research, the optimization of dilute acid pretreatment was performed for enzymatic saccharification of S. salsa. Effect of sulfuric acid concentration, liquid–solid ratio and pretreatment time on xylose and glucose yield in the pretreatment and enzymatic hydrolysis stage was studied with single-factor experiment method. Xylose yield and glucose yield reached a maximum of 18.48g and 25.49g per 100g raw material respectively at the pretreatment condition with 2.6% (w/w) sulfuric acid concentration, 50min, 8:1 liquid–solid ratio (v/w) and 125°C. The changes in compositions of the pretreated S. salsa were also investigated. And the changes in structures of the pretreated S. salsa were characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The results revealed that S. salsa was a potential feedstock for bio-ethanol production and high value-added products.

Study on the influence of various factors in the hydrometallurgical processing of waste printed circuit boards for copper and gold recovery

The present lab-scale experimental study presents the process of leaching waste printed circuit boards (WPCBs) in order to recover gold by thioureation. Preliminary tests have shown that copper adversely affects gold extraction; therefore an oxidative leaching pre-treatment was performed in order to remove base metals. The effects of sulfuric acid concentration, hydrogen peroxide volume and temperature on the metal extraction yield were studied by analysis of variance (ANOVA). The highest copper extraction yields were 76.12% for sample A and 18.29% for sample D, after leaching with 2M H2SO4, 20ml of 30% H2O2 at 30°C for 3h. In order to improve Cu removal, a second leaching was performed only on sample A, resulting in a Cu extraction yield of 90%. Other experiments have shown the negative effect of the stirring rate on copper dissolution. The conditions used for the process of gold extraction by thiourea were: 20g/L thiourea, 6g/L ferric ion, 10g/L sulfuric acid, 600rpm stirring rate. To study the influence of temperature and particle size, this process was tested on pins manually removed from computer central processing units (CPUs) and on waste CPU for 3½h. A gold extraction yield of 69% was obtained after 75% of Cu was removed by a double oxidative leaching treatment of WPCBs with particle sizes smaller than 2mm.

Effect of sulfuric acid concentration on the yield and properties of the bio-oils obtained from the auger and fast pyrolysis of Douglas Fir

The effect of sulfuric acid concentration on the yield and composition of bio-oils obtained from the auger and fluidized bed pyrolysis of Douglas Fir at 500°C have been investigated as a mean to enhance the production of fermentable sugars. The concentration of sulfuric acid in the feedstock was varied between 0 and 0.6mass%. The overall yield of pyrolysis products (gas, bio-oil and char) was comparable for both reactors. The presence of sulfuric acid decreases bio-oil yield and increases water and char yields. The yield of pyrolytic water produced in the auger reactor was higher due to the lower heating rates achieved which favor dehydration reactions. Maximum yields of levoglucosan and fermentable sugars were obtained at concentrations of sulfuric acid of 0.3mass% in the auger reactor and 0.05mass% in the fluidized bed reactor. Dehydration reactions responsible for water and cross linked sugars formation, as observed by the increase in the band at 1654cm−1 fitted in the FTIR, were enhanced as sulfuric acid concentration increases. The dehydration of cellulose in the presence of sulfuric acid also causes a reduction in the yield of acetic acid and acetol. The yields of some lignin derived compounds (lignin oligomers and guaiacols) also decreased substantially when sulfuric acid was added. Potential mechanisms responsible for the phenomena observed are discussed.

Treatment and Recovery Of Sludge Containing Heavy Metals

This work presents the results of wastewater sludge treatment coming from a dismissed industrial site. Sludge sample was collected from an industrial site and treated with sulfuric acid to extract heavy metals (Cu, Ni, Cd and Zn) that are separated by electrodeposition. To determine the best extractive parameters we carried out a study on the effects of sulfuric acid concentration and solid to liquid ratio. To minimize power consumption during the electrodeposition, the cathode used was made in the same material as the extracted metal. In order to have deposition time as similar as possible, the cathode area used was adapted to the concentration of the respective metal. The recovery of each metal was made potentiostatically at different potentials. The results show that for 5g/L solid to liquid ratio more than 99,9% of heavy metals can be removed from the sludge by treating with 0,5M sulfuric acid in less than 2hours. The recovery of heavy metals by reduction was achieved at 99%. The solution, obtained after electrodeposition, contains metals concentrations in agreement with Algerian legislations.