Effect Of Alkaline Additives Research Articles

Migration of nitrogen and phosphorus during supercritical water gasification of sewage sludge: Effect of alkaline additives

The effect of alkaline additives (KOH, NaOH, Ca(OH)2, NaCO3 and K2CO3) on syngas yield, phosphorus (P) and nitrogen (N) migration during supercritical water gasification (SCWG) of sewage sludge were investigated. The alkaline additives elevated the syngas yield by affecting the steam reforming reaction, water-gas shift reaction and methanation reaction. In addition, alkaline additives enriched P and N into the aqueous phase by promoting the dissolution of phosphide (AlP, CaP, and FeP) and the decomposition of nitrogenous organic matter and hydrolysis of nitrile in sludge. The results showed that K2CO3 exhibited the best catalytic effect in these five alkaline additives. In the presence of 0.5 g K2CO3 (5%), the syngas yield was up to 18.2 mol/kg, as well as, 78.2% of P and 80.2% of N were dissolved in the aqueous phase. Moreover, the effects of different K2CO3 additions (5%–11%) on the syngas yield and the migration of N and P were discussed.

Effect of Alkaline Additives over V-Based Catalysts Supported on y- Al2O3 for Propane Oxidative Dehydrogenation

The olefins product are more reactive than the corresponding alkanes, and may easily be super-oxidised into CO and CO2 in selective oxidation of alkanes. The proper balance of acid and base sites on the V-based catalyst surface plays a decisive role in limiting the complete oxidation of alkanes. Therefore, our goal was to evaluate the promoting effect of alkali metals and the support effect using boehmite as precursor for the propane oxidative dehydrogenation (ODH) reaction. Catalysts were prepared via co-impregnation of V and Na or K on a synthesized alumina support. The following characterization techniques were used: N2 adsorption-desorption, X-ray diffraction (XRD), temperature programmed reduction (TPR) and isopropanol decomposition testes to evaluate the acid-base character. The catalyst performance in the propane ODH reaction was evaluated at the O2:C3H8:He molar ratios of 5:2:4, 6:1:4, and 4:3:4. The K-doped catalysts exhibited higher propene selectivity owing to the modification of acid-base character that rendered the weaker interaction between olefinic intermediate and more basic catalyst surface. A high molar fraction of O2 of the reaction mixture minimized coke formation and a high reoxidation rate possibly increased catalytic activity and propene selectivity.

Influence of alkaline additives on main minerals in Baotou rare earth tailings in the process of coal-based magnetizing roasting

The influence of NaOH-Ca(OH)2 on magnetizing roasting of iron minerals and on the decomposition reactions of rare earth minerals during coal-based magnetizing roasting is explored in the present work. The effect of alkaline additives was determined by means of SEM-EDS and X-ray diffraction methods in NaOH-Ca(OH)2-coal-tailings mixtures under optimal magnetizing roasting conditions (mass ratio of NaOH, Ca(OH)2, coal and tailings equal to 2.5: 4.5: 2.5: 100, roasting at 650 °C for 2.5 h). Although NaOH results in an adverse impact on magnetizing roasting of hematite, iron in silicate minerals could be released by NaOH-Ca(OH)2 additive as a form of hematite, which is further reduced to ferromagnetic magnetite. Moreover, the reduction ability of gas is improved in presence of coal and water from decomposition reaction of Ca(OH)2. Regarding the decomposition of bastanasite, no evident effect of NaOH-Ca(OH)2 is observed. The roasted products of pristine bastnasite particles are mainly composed of rare earth oxides (REO) with little fluorine, independent on the use of alkaline additives. No high purity REO were determined in the monazite particle by SEM-EDS, which is mainly decomposed into REO and REFeO3.

Influence of Alkaline Additives and Buffers on Mineral Trapping of CO2 under Mild Conditions

AbstractCarbon dioxide (CO2) gas is the main contributor to climate change. CO2 storage in underground brines and oil‐field brines by mineral trapping has been considered as a promising alternative in order to reduce CO2 emissions. However, permanent storage of CO2 in stable carbonate minerals is greatly dependent on brine pH, being favored over an alkaline pH. The effect of alkaline additives (NaOH, KOH, CaO) and buffer solutions (NaHCO3/NaOH, Na2HPO4/NaOH, NH4Cl/NH4OH) on the mineral trapping of CO2 under mild conditions using a synthetic brine is investigated. The results indicate that both NaOH+NH4Cl/NH4OH and KOH+NH4Cl/NH4OH mixtures promote precipitation mainly of calcium carbonate (CaCO3).

Remediation of electric arc furnace dust leachate by the use of cementitious materials: A column-leaching test

Disposal of industrial solid wastes in a hydrologic environment can cause environmental risks due to the mobility of toxic trace elements. It is increasingly important to find simple and inexpensive treatments to remove undesirable elements from industrial solid wastes. One of the most important problems in the secondary steel mill industry is the disposition of dusts produced from electric arc furnace. A large quantity (10--20 kg) of electric arc furnace dust (EAFD) is generated per ton of steel produced. The Toxicity Characteristic Leaching Procedure (TCLP) shows that the total Cr and Cr (VI) concentrations (9.7 and 6.1 mg/L respectively) from the EAFD studied exceeded the Toxicity Characteristic Regulatory Level. Some heavy metals of EAFD like chromium are toxics and have high solubility. Chromium (VI) is particularly problematic because it must initially be reduced before fixed in an insoluble phase. To counter this problem, the use of ordinary Portland cement (OPC) and ground granulated blast furnace slag (GGBFS) was investigated. Column leaching test was performed to evaluate the leaching of EAFD amended with GGBFS and OPC under dynamic conditions simulating heap leaching. The goal of this study is to fred a simple and economic way to decrease contaminants in the leachate. Test columns have been set up to evaluate the effect of alkaline additives (OPC and GGBFS) on the geochemistry of drainage water. The control column consists of EADF only. A set of columns presents the effect of the addition of 5% by mass of OPC or GGBFS mixed homogeneously with the EAFD. Another set of columns was set up with the same quantities of OPC and GGBFS but concentrated at the base of the EAFD simulating a liner. Columns were fed three times weakly during 1 month. The parameters monitored after each flush of water include leachate volume, pH, electrical conductance and water quality (Cr-Ni-Pb-Zn concentrations). The leaching of the control (EAFD only) presents high Cr concentration. The addition of GGBFS and OPC increases the pH conditions and decreases metal concentrations. The concentration of OPC and GGBFS at the base of the EADF as a liner was the more efficient disposition. The use of a mixture of EAFD with 5% of OPC or GGBFS applied at the base of EADF heap is a simple and economic way to remove contaminant. In spite of a significant decrease in Cr concentration, values remain slightly above regulatory level.

A geochemical study of redox behavior of As in a contaminated aquifer from Sonargaon, Central Bangladesh

Disposal of industrial solid wastes in a hydrologic environment can cause environmental risks due to the mobility of toxic trace elements. It is increasingly important to find simple and inexpensive treatments to remove undesirable elements from industrial solid wastes. One of the most important problems in the secondary steel mill industry is the disposition of dusts produced from electric arc furnace. A large quantity (10--20 kg) of electric arc furnace dust (EAFD) is generated per ton of steel produced. The Toxicity Characteristic Leaching Procedure (TCLP) shows that the total Cr and Cr (VI) concentrations (9.7 and 6.1 mg/L respectively) from the EAFD studied exceeded the Toxicity Characteristic Regulatory Level. Some heavy metals of EAFD like chromium are toxics and have high solubility. Chromium (VI) is particularly problematic because it must initially be reduced before fixed in an insoluble phase. To counter this problem, the use of ordinary Portland cement (OPC) and ground granulated blast furnace slag (GGBFS) was investigated. Column leaching test was performed to evaluate the leaching of EAFD amended with GGBFS and OPC under dynamic conditions simulating heap leaching. The goal of this study is to fred a simple and economic way to decrease contaminants in the leachate. Test columns have been set up to evaluate the effect of alkaline additives (OPC and GGBFS) on the geochemistry of drainage water. The control column consists of EADF only. A set of columns presents the effect of the addition of 5% by mass of OPC or GGBFS mixed homogeneously with the EAFD. Another set of columns was set up with the same quantities of OPC and GGBFS but concentrated at the base of the EAFD simulating a liner. Columns were fed three times weakly during 1 month. The parameters monitored after each flush of water include leachate volume, pH, electrical conductance and water quality (Cr-Ni-Pb-Zn concentrations). The leaching of the control (EAFD only) presents high Cr concentration. The addition of GGBFS and OPC increases the pH conditions and decreases metal concentrations. The concentration of OPC and GGBFS at the base of the EADF as a liner was the more efficient disposition. The use of a mixture of EAFD with 5% of OPC or GGBFS applied at the base of EADF heap is a simple and economic way to remove contaminant. In spite of a significant decrease in Cr concentration, values remain slightly above regulatory level.

Effect of alkaline additives on the thermal properties of bauxite

The dehydration and decomposition bauxite mixed with alkaline compounds were investigated under dynamic and isothermal conditions. Alkaline compounds (CaO or/and Na2CO3) were added to bauxite samples in various mole fractions (0.0, 0.2, 0.4, 0.6, 0.8 and 1.0 of CaO). To determine the effect of alkaline additives on the thermal properties of bauxite, TG, DTG and DTA techniques were used simultaneously under atmospheric conditions.

Effect of Alkaline Additives on the Electrode Reduction of Iodine in Hydrogen Fluoride Gas Sensor

Effect of Alkaline Additives on the Electrode Reduction of Iodine in Hydrogen Fluoride Gas Sensor

Carbonization of coals in the presence of alkaline hydroxides and carbonates: Formation of activated carbons

Pyrolysis of coals in the presence of alkaline compounds may lead to a significant increase of the micropore volume of the resultant carbon. The effect of alkaline additives on the carbonization mechanism of coals is investigated and the physico-chemical reactions which cause the development of the microporosity are determined and discussed.

Effect of alkaline additives on the C−O bond dissociation of adsorbed CO in methanation over Ru/Al2O3 catalyst

By using PSRA (Pulse Surface Reaction Rate Analysis) coupled with EDR (Emissionless Diffuse Reflectance Infrared Spectrometer), it was found that the lower shift of C−O stretching vibration of absorbed CO — caused by the addition of alkali carbonate to Ru/Al2O3 — leads to a decrease in the rate constant for the C−O dond dissociation process of adsorbed CO in methanation.

Surfactant Flooding 2: The Effect of Alkaline Additives on Permeability and Sweep Efficiency

Abstract This paper is the second of a series of papers reporting our examinations of the effects alkaline additives have on dilute surfactant systems for low-tension waterflooding (LTWF). The first paper outlined the effects on interfacial tension (IFT), hardness removal, and surfactant retention by the core material, and how these parameters then affect overall recovery of oil from watered-out cores containing high-hardness brines. This study examines the effects of those chemicals on permeability, sweep efficiency, and sweep symmetry through multipermeable noncommunicating zones. Correlations and possible mechanisms are offered that relate these findings to the earlier work on surfactant retention and hardness removal. The results of these studies indicate that each alkali behaves differently, but all are capable of enhancing the action of the dilute surfactant treatment. Sweep efficiency in three-dimensional (3D) patterns and sweep symmetry through multipermeable noncommunicating zones is increased by the alkaline chemicals. Selective permeability reduction, caused by the reaction with the residual hardness ions, is suspected as a mechanism. Overall, sodium silicate addition to the surfactant flood as a builder was found to produce the best performance because of its ability to inhibit surfactant retention, thereby increasing the recovery of crude before selective permeability reduction occurs. Overall permeability loss is only about 20 to 25% in a core initially containing 4,800 ppm of hardness as CaCOз under our experimental conditions.