Presence Of Sodium Sulfate Research Articles

Recovery of lithium carbonate crystals from a high salinity solution using membrane crystallizer with concentration and temperature gradients

The increasing global demand for lithium, driven by the rapid expansion of electric vehicles and energy storage systems, underlines the need for efficient lithium recovery technologies. This study explored the potential of using the fractional-submerged membrane distillation crystallizer (F-SMDC) process for recovering lithium carbonate (Li2CO3) crystals from high-salinity solutions. The F-SMDC integrates membrane distillation and cooling crystallization processes within a single reactor, utilizing concentration gradient (CG) and temperature gradient (TG) to enhance water recovery and resource crystallization. We investigated the behaviors of Li2CO3 crystallization, CG, and TG in presence of sodium sulfate (Na2SO4). Our results indicated that the low temperature-sensitive solubility of Li2CO3 is the current challenge for CG generation, as Li2CO3 crystallization tends to occur at the top of the reactor (at higher temperatures). Addition of Na2SO4 facilitated CG generation, improving the overall performance of the F-SMDC process for Li2CO3 crystallization at the bottom of the reactor. However, issues such as Li2CO3 crystal deposition on the membrane surface, changes in the CG tendency, and flux stabilization timing were observed. Thus, although F-SMDC shows promise for Li2CO3 recovery from high-salinity solutions, further process optimization is necessary to address the challenges of Li2CO3 crystallization and membrane fouling. Potential integration of additional crystallization techniques could enhance selectivity and recovery efficiency.

Noodle Production for Diabetics from Modified Green Banana Starch by Phosphate Cross‐Linking

AbstractThe development of Green banana (GB) starch in prebiotic foods to address health problems such as diabetes. It is modified by phosphate cross‐linking to increase the resistant starch content, improve functional properties, and reduce digestible starch consumption. The starch is modified using a mixture of sodium trimetaphosphate (STMP) and sodium tripolyphosphate (STPP) with 6 to 12 wt%ratios in the presence of sodium sulfate. The results showed an increase in phosphorus content from 0.18% to 0.45% corresponding to the increase in sodium trimetaphosphate/sodium tripolyphosphate ratios. Resistant starch reached 60 wt% after increasing the concentration of phosphate agent above 10 wt% and rapidly digestible starch decreased significantly. Accordingly, the physicochemical properties of starch changed significantly. Phosphate cross‐linking led to disruption of the crystalline structure of starch granules and fragmentation, reducing enthalpy and increasing gelatinization temperature. The oil and water absorption and freeze‐thaw stability of treated starch increased. While water absorption and solubility index of starch decreased significantly as the result of phosphate cross‐linking. Modified starch is used for the production of rice noodles. From 10 to 30 wt% of 10P modified starch mixed, cooking fracture rate is not more than 10% and resistant starch content is over 41 wt%.

State of conservation of an industrial brick masonry chimney: a case-study in Montijo, Portugal

AbstractIndustrial masonry chimneys became widespread in the mid-19th century and were eventually integrated into urban landscapes, gaining significance as symbolic historical remnants of local industries. This poses new challenges, particularly concerning the safety of populations and goods, as well as the preservation of the now-historical structures. In this article, we assess the conservation status of the 45-meter-high chimney of the former cork processing factory Mundet, located in Montijo, Portugal. The study involved a structural survey conducted using height access equipment, along with an investigation to diagnose moisture and salt decay at the base of the chimney. The later included measuring current and hygroscopic moisture distributions, as well as XRD characterization of brick and mortar samples. At the chimney’s base, salt crystallization causes efflorescence and erosion leading to masonry disintegration. This is associated with rising damp and the presence of sodium sulfate in the brick and sodium chloride in the mortar. In the shaft, mortar erosion becomes more pronounced as we ascend. At the crown, extensive mortar erosion and limited compression have caused the NE-facing half to disappear, while the rest is at risk of imminent collapse. Damage mitigation measures to address this situation are proposed.

Effect of the anode material, applied current and reactor configuration on the atenolol toxicity during an electrooxidation process

Atenolol (ATL) is a beta-blocker pharmaceutical product which is excreted mainly unchanged and may represent a long-term risk for organisms present in the sea and in fresh water. Due to its low biodegradation rate, electrochemical advanced oxidation processes (EAOPs) can be used to remove this compound. In this work, ATL ecotoxicity was analyzed in the presence of sodium sulfate (Na2SO4), which is widely used as supporting electrolyte in EAOPs. Ecotoxicity values were expressed as the pollutant concentration that leads to a 50% inhibition of the root elongation of Lactuca sativa seeds in relation to the control (EC50(5 days)). The obtained values for ATL showed an EC50(5 days) of 1377 mg L−1 towards Lactuca sativa. When Na2SO4 was added, the toxicity of the sample increased but no synergy was detected between both compounds. With 2 g L−1 Na2SO4, ATL showed an EC50(5 days) of 972 mg L−1; and with 4 g L−1 Na2SO4 and higher concentrations, EC50 value for ATL was 0 mg L−1. Statistical tools were used to obtain the zones of the [ATL]-[Na2SO4] plane which are toxic towards Lactuca sativa.Solutions containing ATL and Na2SO4 were treated by electrooxidation. Two anode materials (a boron-doped diamond electrode and a microporous Sb-doped SnO2 ceramic one); three operation currents (0.4, 0.6 and 1 A); and two reactor configurations (one-compartment reactor and two-compartment reactor separated by a cation exchange membrane) were used. Lactuca sativa seeds and Vibrio fischeri bacterium tests were employed to evaluate the toxicity of the solutions before and after applying the electrooxidation process. In all the tests, the ecotoxicity of the treated sample increased. This fact is owing to the persulfate presence in the solution due to the sulfate electrochemical oxidation. Nevertheless, none of the final samples were toxic towards Vibrio fischeri because ecotoxicity values were lower than 10 TU; and, in the case of the one-compartment reactor, practically all of them were also non-toxic towards Lactuca sativa. The toxicity of the treated samples increased when using the two-compartment reactor in the presence of the BDD anode, and when the operation current was increased. This is attributed to the highest formation of persulfates. Amongst all the tests performed in this work, the lowest toxicity value (i.e., 3 TU) together with the complete mineralization and degradation degrees was achieved with the two-compartment reactor using the BDD anode and operating at 0.6 A.

Modified Paving Block- a Solution for Waste Plastic into Value added Applications for Mathura-Vrindavan City

This investigation is focused on the conversion of waste plastic into modified pavement interlock block (Bitumen: quarry dust: coarse aggregate: rice straw ash: waste plastic:: 5% by weight of aggregate mix : 1:2:2% by weight of aggregate mix : 8% by weight of Bitumen) for Mathura Vrindavan city. The aim of this work is to reduce the rapid accumulation of waste plastic at religious places/ tourist spot by throwing the PET bottles in Mathura Vrindavan city. With the application of these experimental results, can make economical and environment friendly paving block. For each 6.7 no. of paving block, 1 PET bottle (38gm) of 1lit volume consumed hence in 10m2 areas 55.37no. bottles can be utilized. From Marshall Stability- Flow value test, 8% of PET plastic is optimum value which can use in manufacturing of modified paving block with 80/100 grade of bitumen. The average compressive strength of these blocks at 3 and 7 days is15.94MPa and 24.2MPa and the water absorption value is approximately 0.27%. In the presence of sodium sulphate (250gm in 1lit water) loss of weight is around 7.7%. It was estimated that the manufacturing cost of designed paving block is 12Rs. whereas concrete paving block of same size is Rs. 17. Hence its cost quite low as compared to conventional block. Keywords- Mathurav vrindavan city, waste plastic, Bitumen

Degradation of carbendazim in aqueous solution by different settings of photochemical and electrochemical oxidation processes

The present study analyzed the performance of photochemical and electrochemical techniques in the degradation and mineralization of the pesticide carbendazim (CBZ). Direct photolysis (DP), heterogeneous photocatalysis (HP), photoelectrocatalysis (PEC), and electrochemical oxidation (EO) were tested, and the influence of UV radiation, current density (j), and supporting electrolyte concentration were evaluated. The results suggest that CBZ is only degraded by DP when UV-C254nm is used. For HP, the CBZ degradation was observed both when UV-A365nm or UV-C254nm were used, which is related to the reactive oxygen species (ROS) formed by the photocatalytic activity (photon-ROS). Neither DP nor HP were able to mineralize CBZ, demonstrating its resistance to photomediated processes. For EO, regardless of the j, there were higher CBZ degradation and mineralization than those observed when using DP and HP. The increase in the supporting electrolyte concentration (Na2SO4) did not affect the levels of degradation and mineralization of CBZ. Concerning the PEC, a CBZ mineralization of 52.2% was accomplished. These findings demonstrate that the EO is the main pathway for CBZ mineralization, suggesting an additional effect of the electro-ROS on the photon-ROS and UV-C254nm. The values of mineralization, kinetics, and half-life show that PEC UV-C254nm with a j of 15 mA cm−2 was the best setting for the degradation and mineralization of CBZ. However, when the values of specific energy consumption were considered for industrial applications, the use of EO with a j of 3 mA cm−2 and 4 g L−1 of Na2SO2 becomes more attractive. The assessment of by-products formed after this best cost-efficient treatment setting revealed the presence of aromatic and aliphatic compounds from CBZ degradation. Acute phytotoxicity results showed that the presence of sodium sulfate can be a representative factor regarding the toxicity of samples treated in electrochemical systems.

An Approach for Linen Fabrics Coloring and Antibacterial Activity by Cumin in Combination with Nano Copper and Iron

ABSTRACT Flax fibers have always a special place among the whole consumed fibers owing to customer demands related with its characteristic features. This is why investigating alternative finishing methods to transfer different features to these fibers along with coloration is an important issue. In this study, it is aimed to color linen fabrics with cumin seeds and to diversify the obtained colors by using sodium sulfate (Na2SO4) in different amounts during the extraction and dyeing periods as well. Additionally, copper and iron in powder form was used during cumin-based finishing processes to achieve coloration and antibacterial features. To see the effect of using sodium sulfate and copper/iron powders in finishing, the solely cumin-based dyeings were also carried out as well. As a result of the study, it was observed that cumin seeds can be used for coloring the fabrics and the presence of sodium sulfate in extraction and so in dyeing period enhance the obtained colors darker which means lower L* values in CIE L*a*b* color space. Meanwhile the color yields (K/S) become higher too. Furthermore, it was also found that the presence of copper nano-powder during dyeing has a significant effect on color yields and provide antibacterial activity against Escherichia coli and Staphylococcus aureus.

Modeling of the Refractive Index for the Systems MX+H2O, M2X+H2O, H3BO3+MX+H2O, and H3BO3+M2X+H2O. M = K+, Na+, or Li+ and X = Cl− or SO42−

The modeling of the refractive index for binary aqueous solutions of boric acid, sodium chloride, potassium chloride, sodium sulfate, lithium sulfate, and potassium sulfate, as well as ternary aqueous solutions of boric acid in the presence of sodium sulfate, lithium sulfate, or potassium chloride, is reported. The refraction index was represented by molar refraction. It was described as the sum of solutes’ partial molar refraction and solvent molar refraction. The solutes’ partial molar refraction was estimated from the molar refraction of the binary solutions. The excess molar refraction for these systems was described with the equation of Wang et al. The polarizability of the solutes present in the studied systems was estimated using the Lorenz–Lorenz relation. The results showed the model is appropriate for describing the systems studied; the interactions of boric acid, sodium, potassium, lithium, chloride, and sulfate ions with water molecules are relevant to explain the molar refraction and refractive index, and those for the binary systems of lithium chloride and sodium chloride are also relevant the ion–ion interactions. The model is robust and presents estimation capabilities within and beyond the concentrations and temperature range studied. Therefore, the outcomes represent valuable information to understand and follow the industrial processing of natural brines.

Improvement of continuous technology of electrochemical synthesis of nickel hydroxide by implementation of solution recycling

Nickel hydroxide is widely used in supercapacitors, alkaline batteries, for the electrocatalytic oxidation of organic contaminants, etc. Due to their electrochemical activity, Ni(OH)2 (α+β) samples with a layer structure synthesized in a slit diaphragm electrolyzer are the most promising. To improve the continuous technology of electrochemical synthesis of nickel hydroxide, the possibility of recycling the spent catholyte containing sodium sulfate was determined. For this, samples of nickel hydroxide were synthesized from a solution of nickel sulfate in the presence of sodium sulfate with concentrations of 40, 60, 80, 100, and 120 g/L. The crystal structure of the samples was studied by X-ray phase analysis; the electrochemical properties were studied by the method of cyclic voltammetry. It was shown that the base sample obtained without the presence of sodium sulfate was a monophase layered (α+β) structure with a high content of α-modification. The crystallinity of the sample was not high. It was revealed that the presence of sodium sulfate led to a decrease in the crystallinity of nickel hydroxide due to an increase in the electrical conductivity of the solution and a decrease in the voltage in the electrolyzer. Cyclic voltramperometry showed that synthesis in a slit diaphragm electrolyzer in the presence of Na2SO4 (40–80 g/L) did not lead to a significant change in the electrochemical activity of nickel hydroxide samples. An increase in the concentration of sodium sulfate in the catholyte to 100–120 g/L led to an increase in electrochemical activity – the specific current of the discharge peak was 3.7–3.9 A/g (compared to 2.1 A/g for the reference sample).A comprehensive analysis of the characteristics of nickel hydroxide samples synthesized in the presence of sodium sulfate revealed the possibility and prospects of recycling the spent catholyte in a continuous technology for producing Ni(OH)2 in a slit diaphragm electrolyzer. It was revealed that when introducing recycling, it was recommended to maintain a high concentration of sodium sulfate (80–100 g/L)

The Research of the Carbothermic Solid–Phase Red Mud Reduction Process in the Presence of Sodium Sulphate


 
 
 Russia has accumulated about 600 million tons of the red mud that is alumina production waste generated by Bayer method, but currently only a small amount of the total accumulated red mud is recycled. Solid–phase carbothermic reduction of red mud in the presence of sodium salts with magnetic separation can be a promising method for iron extraction. In this paper, the effect of the addition of sodium sulphate on the reduction of iron–containing phases and the growth of iron grains during solid–phase carbothermic reduction of red mud was investigated. The results show that 10% sodium sulphate additive significantly accelerate the growth of reduced iron grains, but decrease the degree of its reduction at temperatures above 1100∘C. The explanation of mechanism of sodium sulphate effect on the iron grain growth was proposed. Optimization of sodium sulphate amount, temperature and holding time can lead the development of effective technology of iron extraction from red mud by solid–phase carbothermic reduction.
 Keywords: red mud, solid–phase carbothermic reduction, sodium sulphate
 
 

Effect of Sodium Sulfate on Nucleation Behavior and the Crystal Morphology of Taurine

AbstractTwo theoretical methods, self‐consistent Nývlt‐like approach and Sangwal's classical 3D nucleation theory‐based method, are employed to analyze the effects of additives (sodium sulfate) on the nucleation behavior of taurine. By correlating the measured metastable zone width of taurine containing different sodium sulfate concentrations, with saturation temperature and cooling rate, nucleation kinetic parameters in both two methods are determined. Fitting results demonstrate that higher sodium sulfate concentration results in the increase of solid–liquid interfacial energy γ, contrarily higher saturation temperature has the opposite effect thus changing of nucleation rate. The molecular modeling techniques are then applied to investigate the changes in the morphology of taurine which caused by the presence of sodium sulfate. Through molecular dynamic simulations, the interaction energy of sodium sulfate with taurine crystal faces are obviously larger than those of taurine and these differences on the (011) and (11‐1) are more significant than those on (021) and (111) faces. As a result, the growth of (011) and (11‐1) faces is inhibited and the morphology of taurine crystal is modified from needle to columnar. The influence of sodium sulfate on taurine studied in this work provides theoretical guidance for industrial production.

Mechanism of Complexation of Cucurbiturils with Styryl Dyes in the Presence of Sodium Cations

The complexation of styryl dyes 4-[(E)-2-(3,4-dimethoxyphenyl)]-1-ethylpyridinium perchlorate and trans-4-[4-(dimethylamino)styryl]-1-methylpyridinium iodide with cucurbit[n]urils (CBn) (n = 6, 7) in aqueous solutions in the presence of sodium sulfate with a concentration of 0 to 1 mol/L has been studied by stationary and time-resolved optical spectroscopy, electrochemical, and quantum chemical methods. Adding the electrolyte to the solution decomposes 1 : 1 inclusion complexes with the dyes (D+ · CBn) due to competitive formation of complexes of the cavitand with sodium cations: Na+ · CBn and Na+ · CBn · Na+. Their total formation constants have been determined to be β = 2760 and 168 600 M−2 for CB7 and CB6, respectively, which agrees with the results of quantum chemical calculations. At the same time, no evidence of the presence of Na+ · CBn · D+ type complexes has been found in solutions.

Modeling of the density, viscosity and electrical conductivity of aqueous solutions saturated in boric acid in presence of lithium sulfate or sodium sulfate at 293.15 to 313.15 K

The modeling of the density, viscosity and electrical conductivity of aqueous solutions saturated with boric acid, in the presence of sodium sulfate or lithium sulfate, are presented. The salt concentrations range studied were from (0 to 3.3242) mol·kg−1 for sodium sulfate and from (0 to 2.9336) mol·kg−1 for lithium sulfate at temperatures from (293.15 to 313.15) K and at 1 atm pressure. A model for the density was derived using the Pitzer model. The Eyring's absolute rate theory and the Pitzer model were combined to represent the viscosity. The Casteel-Amis equation was modified to describe the electrical conductivity with temperature and boric acid effects where necessary. The results showed that the models successfully represented the properties studied and are robust for estimation purposes within and beyond the experimental range studied. Also, it was found that short range interactions of boric acid, sulfate, sodium and lithium ions with water molecules are relevant to determine the volumetric and transport properties of these solutions and that the electrical conductivity is determined by charged species (Na+, SO42−, NaSO4−, HSO4− and Li+, SO42−, LiSO4−) and the solution viscosity; that is mainly influenced by these salts concentrations, boric acid solubility behavior with these salts and temperature. This is valuable information to improve the processes of boric acid production.

Resistance to Chemical Attack of Hybrid Fly Ash-Based Alkali-Activated Concretes.

The environmental impacts related to Portland cement production in terms of energy consumption, the massive use of natural resources and CO2 emissions have led to the search for alternative cementitious materials. Among these materials, alkali-activated cements based on fly ash (FA) have been considered for concrete production with greater sustainability. In the present article, the chemical durability properties (resistance to sulphates, chloride permeability, and resistance to carbonation) of a hybrid alkali-activated concrete based on fly ash–ordinary Portland cement (FA/OPC) with proportions of 80%/20% were evaluated. It is noted that the FA was a low-quality pozzolan with a high unburned carbon content (20.67%). The results indicated that FA/OPC concrete had good durability with respect to the OPC concrete, with 95% less expansion in the presence of sodium sulphate and a 2% strength loss at 1100 days, compared with the 56% strength loss of the OPC concrete. In addition, FA/OPC showed lower chloride permeability. On the contrary, the FA/OPC was more susceptible to carbonation. However, the residual compressive strength was 23 MPa at 360 days of CO2 exposure. Based on the results, FA/OPC, using this type of FA, can be used as a replacement for OPC in the presence of these aggressive agents in the service environment.

Advanced Method for Recycling Red Mud by Carbothermal Solid-Phase Reduction Using Sodium Sulfite

The paper presents the results of studying the iron grain growth mechanism during carbothermal solidphase reduction of red mud in the presence of sodium sulfate. It was shown that the main mechanism of iron grain growth involves the formation of low-melting-point surface-active iron-sulfur compounds along the grain boundaries, which significantly accelerates their agglomeration process. The obtained results confirm a positive effect of the sodium sulfate additives on the process of iron grain growth during solid-phase carbothermal reduction of red mud, which makes it possible to improve the efficiency of subsequent magnetic separation.

Correlations between the kinetics and the mechanisms of hot corrosion of pure nickel at 700 °C

This study investigates the kinetics of hot corrosion of pure nickel exposed to different testing conditions at 700 °C. Whereas nickel underwent pure oxidation when exposed to synthetic air only, the addition of 0.5% SO2/SO3 induced oxidation-sulphidation and considerably increased the corrosion kinetics. In the presence of sodium sulphate (Na2SO4), Ni-S liquid solutions systematically formed at the metal/scale interface. This was attributed to the shielding effect of Na2SO4 implying negative pO2 and pSO3 gradients from the gas/salt interface towards the scale/salt interface. The influence of thermal cycling as well as the testing method (i.e. half-embedding and salt-recoating) was also elucidated.

Chemical and isotopic signatures of hot springs from east-central Sonora State, Mexico: a new prospection survey of promissory low-to-medium temperature geothermal systems

A promissory low-to-medium temperature geothermal system located in Sonora (Mexico) has been studied. In the present work, a detailed geochemical survey was carried out to understand the hydrogeochemical signatures of hot spring waters. A field work campaign was conducted for collecting water samples from twelve hot springs placed in four major zones (NW, NE, C, and S). The collected samples were analysed by chemical and isotopic methods for determining their chemical (major and trace elements) and isotopic (18O/16O and D/H) compositions. Using geochemometric analyses of the fluid composition and fractionation, depletion and enrichment processes exhibited by major and trace elements were analysed.
 Hydrogeochemical classification was used to indicate the presence of sodium-sulphate (Na-SO4) waters in the North (NW and NE) and South hydrothermal zones; whereas calcium-magnesium-bicarbonate (Ca-Mg-HCO3) waters were identified for the Central zone. Some hot spring waters located in the NE zone were also typified as sodium-bicarbonate (Na-HCO3). In relation to the isotopic signatures of 18O/16O and D/H, four water samples from NE and C zones lie near to the global meteoric water line; whereas the remaining eight samples showed a shift for both oxygen and deuterium isotopes. A mixing line with a small shift of δ18O was identified and used as a proxy to discriminate waters with different isotopic signatures.
 After applying a geochemometric outliers detection/rejection and an iterative ANOVA statistical test, the mean temperature inferred from the most reliable solute geothermometers was 149±40 °C, which suggests to be considered as the minimum value of the reservoir temperature. As most of the hot spring waters fall outside of the full equilibrium curve, the original reservoir conditions were corrected by using a mixing conductive model, which predicted a deep equilibrium temperature of 210±11 °C. As this temperature is considerably higher than the mean temperature inferred from the geothermometers, it was suggested as an optimistic maximum reservoir temperature of the Sonora geothermal system.
 Using 150 °C and 200 °C as rounded-off reservoir temperatures (or min-max estimates), geochemical equilibria modelling based on fluid-mineral stability diagrams was carried out. An equilibrium process among local hydrothermal waters and albite-potassium feldespar and muscovite-prehnite-laumontite mineral assemblages was found. These minerals were proposed as representative mineral assemblages of low-grade metamorphism, which seems to indicate that the geothermal fluid equilibria were probably reached within the intermediate to acidic volcanic rocks from the Tarahumara Formation.

Phosphate-based treatments for consolidation of salt-bearing Globigerina limestone

Phosphate-based treatments have proven to be effective for consolidation of porous limestone. However, application on salt-laden stone must be evaluated, as salt-weathering is among the main deterioration phenomena for this lithotype and salts present in the stone can interfere with the outcome of consolidation. For this reason, here, the phosphate-based consolidant was tested on a salt-bearing porous limestone (Globigerina limestone). To achieve salt contamination and to induce weathering, stone samples were subjected to crystallization cycles in sodium sulfate, which is among the most common and damaging salts that affect limestone on site. Phase formation and distribution of the consolidant were evaluated in the presence of salts. The treatment efficacy was investigated in comparison with ethyl silicate, which is currently the most used consolidant for porous limestone. Promising results were obtained, indicating that the presence of sodium sulfate does not hamper penetration of the phosphate-based consolidant. By penetrating deeply into the stone and sealing cracks caused by weathering, the consolidant enhances strength and stiffness. Moreover, the presence of salts does not interfere with the formation of calcium phosphates, hydroxyapatite being the only phase to be detected. These results indicate that the phosphate-based treatment is suitable for consolidation of limestone, even when contaminated with salt.

Raising the Efficiency of Electroflotation Extraction of Metals in Multicomponent Systems from Aqueous Media

Specific features of the electroflotation extraction of hydroxides of nonferrous metals (Cu2+, Ni2+, Zn2+, Cr3+, Fe3+) from a five-component system in the presence of sodium sulfate as supporting electrolyte were examined. The fundamental aspects of the extraction process upon introduction into the system of surfactants of varied nature and flocculants were determined. It was shown that addition of a nonionogenic flocculant N-300 makes it possible to raise the efficiency and stabilize the process of the electroflotation extraction of difficultly soluble metal hydroxides contained in multicomponent systems from wastewater formed in various galvanic shops, with the degrees of extraction possibly reaching a value of 97%.

Part 2

PurposeThe purpose of this study is to optimize single-bath dyeing process of wool and silk blend, to achieve uniform colour strength for both the fibre after the dyeing process. Due to different absorption characteristics of wool and silk, two-stage dyeing is preferred in the industry. If the fibres are dyed together, the wool fibre becomes darker and the silk fibre becomes lighter after the dyeing process. Solid dyeing effect can be achieved using a single-bath dyeing process.Design/methodology/approachThe dye-acceptor sites in the wool fibre are first blocked using one commercial syntan Mesitol HWS. Then, the syntan-treated wool and silk fibres (80:20 blend ratios) are dyed with Telon Navy AMF dyes in the presence of sodium sulphate. To explore the influence of Syntan, sodium sulphate and the experimental conditions on the dyeing process and to optimize the process, central composite design (CCD) of four factors and three levels was tested.FindingsThe design process is optimized using four independent variables: Mesitol HWS concentration, sodium sulphate concentration, pH of dyebath and temperature of dyeing. Three levels of Mesitol HWS concentration (5, 10 and 15 per cent), sodium sulphate concentration (10, 20 and 30 per cent), pH (2.5, 4 and 5.5) and temperature of dyeing (70, 80 and 900°C) were selected for this study. These variables are optimized using response surface regression equation of the ratio of K/S wool and K/S silk. The predicted equation matched well with the experimental data.Originality/valueThis paper proposes the use of one-bath dyeing process of wool and silk blend fabric to reduce the dyeing time, process step and to save water.