Initial pH Value Research Articles

Three-Dimensional Electrochemical Oxidation System with RuO2-IrO2/Ti as the Anode for Ammonia Wastewater Treatment

In this study, a three-dimensional electrochemical oxidation system was constructed to treat ammonia nitrogen wastewater generated from the tail gas absorption of a methionine producer by using a homemade MAC mixed with a GAC at a mass ratio of 1:2 as the particle electrode, with a RuO2-IrO2/Ti polar plate as the anode and a stainless steel plate as the cathode. The effects of current density, initial pH value of wastewater, plate spacing, NaCl concentration and particle filling amount on CODCr and NH4+-N removal were investigated through single-factor experiments, and the removal pathways of CODCr and NH4+-N under the system were initially explored via cyclic voltammetry curves, scanning electron microscopy and tertiary butanol quenching experiments. The experimental results showed that the average removal rate of CODCr was 91.03% and that of NH4+-N was 98.89% after electrolysis for 5 h under the conditions of a current density of 40 mA/cm2, no pH adjustment, the spacing of the electrode plates of 8 cm, the NaCl dosing concentration of 1 g/L, and the particle filling amount of 400 g/L. Under this experimental condition, the removal of CODCr occurred mainly through the indirect oxidation of active chlorine and ·OH, and the removal of NH4+-N mainly through the indirect oxidation of active chlorine.

Intensive Treatment of Organic Wastewater by Three-Dimensional Electrode System within Mn-Loaded Steel Slag as Catalytic Particle Electrodes.

Developing a green, low-carbon, and circular economic system is the key to achieving carbon neutrality. This study investigated the organics removal efficiency in a three-dimensional electrode reactor (3DER) constructed from repurposed industrial solid waste, i.e., Mn-loaded steel slag, as the catalytic particle electrodes (CPE). The CPE, a micron-grade material consisting primarily of transition metals, including Fe and Mn, exhibited excellent electric conductivity, catalytic ability, and recyclability. High rhodamine B (RhB) removal efficiency in the 3DER was observed through a physical modelling experiment. The optimal operating condition was determined through a single-factor experiment in which 5.0 g·L-1 CPE and 3 mM peroxymonosulfate (PMS) were added to a 200 mL solution of 10 mM RhB under a current intensity of 0.5 A and a 1.5 to 2.0 cm distance between the 2D electrodes. When the initial pH value of the simulated solution was 3 to 9, the RhB removal rate exceeded 96% after 20 min reaction. In addition, the main reactive oxidation species in the 3DER were determined. The results illustrated that HO• and SO4•- both existed, but that the contribution of SO4•- to RhB removal was much lower than that of HO• in the 3DER. In summary, this research provides information on the potential of the 3DER for removing refractory organics from water.

Sustainable cotton dyeing with reactive dyes in the recycled dyeing wastewater

Purpose This paper aims to find a suitable solution to degrade the C.I. Reactive Red 24 (RR24) dyeing wastewater by using sodium persulphate to recycle water and inorganic salts. Design/methodology/approach The effects of temperature, the concentration of inorganic salts and Na2CO3 and the initial pH value on the degradation of RR24 were studied. Furthermore, the relationship between free radicals and RR24 degradation effect was investigated. Microscopic routes and mechanisms of dye degradation were further confirmed by testing the degradation karyoplasmic ratio of the product. The feasibility of the one-bath cyclic dyeing in the recycled dyeing wastewater was confirmed through the properties of dye utilization and color parameters. Findings The appropriate conditions were 0.3 g/L of sodium persulphate and treatment at 95°C for 30 min, which resulted in a decolorization rate of 98.4% for the dyeing wastewater. Acidic conditions are conducive to rapid degradation of dyes, while ·OH or SO4−· have a destructive effect on dyes under alkaline conditions. In the early stage of degradation, ·OH played a major role in the degradation of dyes. For sustainable cyclic dyeing of RR24, inorganic salts were reused in this dyeing process and dye uptake increased with the times of cycles. After the fixation, some Na2CO3 may be converted to other salts, thereby increasing the dye uptake in subsequent cyclic staining. However, it has little impact on the dye exhaustion rate and color parameters of dyed fabrics. Originality/value The recommended technology not only reduces the quantity of dyeing wastewater but also enables the recycling of inorganic salts and water, which meets the requirements of sustainable development and clean production.

The physical quality of elephant grass silage with tannin extract from coffee husk

Forage is a major feed that determines the success of livestock farming, especially ruminants. The silage is one technique to preserve forage to maintain the availability of forage all year. Microbes have an important role in the silage process, microbes can break down nutrient components of silage, including protein. Protein is one of the primary nutrients for animals, tannin compound of coffee husk can be used to maintain protein compounds in the silage. Tannin is a bioactive compound from the extract of coffee husk that is non-toxic, organic, and classified as polyphenols. This research purpose was to know the effect of adding an additive of tannin coffee husk on the physical quality of elephant grass silage. The research was analyzed using a T-Test design with 2 treatments and 5 replications (T0: elephant grass + 2% molasses; T1: elephant grass + 2% molasses + coffee husk tannin). The results indicated that no significant difference in the added tannin extract on the final and initial pH value and organoleptic characteristics of elephant grass silage. The conclusion of the research was the tannin extract of coffee husk can maintain the protein content of elephant grass silage in the ensilage process.

The relationship between the initial pH and neurological outcome in patients with out-of-hospital cardiac arrest is affected by the status of recovery of spontaneous circulation on hospital arrival.

The early prediction of neurological outcomes is useful for out-of-hospital cardiac arrest (OHCA). The initial pH was associated with neurological outcomes, but the values varied among the studies. Patients admitted to our division with OHCA of cardiac origin between January 2015 and December 2022 were retrospectively examined (N = 199). A good neurological outcome was defined as a Glasgow-Pittsburgh cerebral performance category (CPC) of 1-2 at discharge. Patients were divided according to the achievement of recovery of spontaneous circulation (ROSC) on hospital arrival, and the efficacy of pH in predicting good neurological outcomes was compared. In patients with ROSC on hospital arrival (N = 100), the initial pH values for good and poor neurological outcomes were 7.26 ± 0.14 and 7.09 ± 0.18, respectively (p < 0.001). In patients without ROSC on hospital arrival (N = 99), the initial pH values for good and poor neurological outcomes were 7.06 ± 0.23 and 6.92 ± 0.15, respectively (p = 0.007). The pH associated with good neurological outcome was much lower in patients without ROSC than in those with ROSC on hospital arrival (P = 0.003). A higher initial pH is associated with good neurological outcomes in patients with OHCA. However, the pH for a good or poor neurological outcome depends on the ROSC status on hospital arrival.

Synthesis of Nano-silica Oxide for Heavy Metal Decontamination from Aqueous Solutions

In the current study, nano-silica oxide (nano-SiO2) was fabricated via the sol-gel technique. Then, the prepared nano-SiO2 was characterized using X-ray diffractometer (XRD), transmission electron microscopy (TEM) coupled with energy-dispersive X-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and Brunauer-Emmett-Teller (BET) specific surface area analysis. Furthermore, the fabricated nano-SiO2 was applied for the adsorption of lead Pb (II) and chromium Cr (VI) from aqueous solutions. Additionally, the influence of different operating factors such as contact time (0–180 min), initial pH (1–11), nano-SiO2 dose (0.1–8 g L−1), initial metal ion concentration (5–100 mg L−1), and the temperature (30–85 °C) was investigated. The nano-SiO2 doses of 0.5 and 1 g L−1 were selected as the optimal adsorbent dose for the removal of Pb (II) and Cr (VI), respectively. These doses achieved a removal efficiency of 82.3% and 78.5% for Pb (II) and Cr (VI), after 60 and 90 min, at initial pH values of 5 and 2, respectively, using 10 mg L−1 initial metal concentration, and at room temperature. Lastly, kinetic and equilibrium studies were competently fitted using the pseudo-second-order and Freundlich models, respectively. Adsorption thermodynamic studies designate the spontaneous and thermodynamic nature of the adsorption process. These results reveal the efficiency of the fabricated nano-SiO2 as an adsorbent for heavy metal removal from aqueous solutions.Graphical

Effect of the initial pH of the culture medium on the nutrient consumption pattern of Bifidobacterium animalis subsp. lactis Bb12 and the improvement of acid resistance by purine and pyrimidine compounds.

During fermentation, the accumulation of acidic products can induce media acidification, which restrains the growth of Bifidobacterium animalis subsp. lactis Bb12 (Bb12). This study investigated the nutrient consumption patterns of Bb12 under acid stress and effects of specific nutrients on the acid resistance of Bb12. Bb12 was cultured in chemically defined medium (CDM) at different initial pH values. Nutrient consumption patterns were analyzed in CDM at pH 5.3, 5.7, and 6.7. The patterns varied with pH: Asp+Asn had the highest consumption rate at pH 5.3 and 5.7, while Ala was predominant at pH 6.7. Regardless of the pH levels (5.3, 5.7, or 6.7), ascorbic acid, adenine, and Fe2+ were vitamins, nucleobases, and metal ions with the highest consumption rates, respectively. Nutrients whose consumption rates exceeded 50% were added individually in CDM at pH 5.3, 5.7, and 6.7. It was demonstrated that only some of them could promote the growth of Bb12. Mixed nutrients that could promote the growth of Bb12 were added to three different CDM. In CDM at pH 5.3, 5.7, and 6.7, it was found that the viable cell count of Bb12 was the highest after adding mixed nutrients, which were 8.87, 9.02, and 9.10 log CFU ml-1, respectively. The findings suggest that the initial pH of the culture medium affects the nutrient consumption patterns of Bb12. Specific nutrients can enhance the growth of Bb12 under acidic conditions and increase its acid resistance.

ZIF-8 metal-organic network/poly(vinyl alcohol) composite for adsorptive removal of various organic dyes

The removal of organic dyes from wastewater is crucial for environmental protection and water treatment. In this study, a ZIF-8/poly(vinyl alcohol) (PVA) composite was prepared for highly efficient dye adsorption using the contra-diffusion method. We investigated the conditions for ZIF-8-PVA to adsorb congo red (CR), including the influences of contact times, initial CR concentrations, pH values, and cyclic use. The results demonstrated that ZIF-8-PVA had a high Brunauer-Emmett-Teller (BET) surface area of 1704.03 m2/g. It exhibited a high removal efficiency of 98.43 % for CR, and its maximum adsorption capacity was 829.39 mg/g. After six cycles of adsorption, the removal efficiency of CR remained over 94.36 %. The removal efficiency of CR under a range of pH from 3 to 10 was consistently over 96.30 %. Moreover, ZIF-8-PVA also displayed adsorption capacity for various cationic and anionic dyes. The adsorption process aligned well with both the Langmuir model and the pseudo-second-order kinetic model. Based on FTIR, XPS, and swelling degree analyses, the adsorption mechanism was elucidated. Due to its universality and reusability, ZIF-8-PVA is suitable for practical application.

Growth kinetics and patulin production by Penicillium setosum in pineapple juice under different temperatures and initial pH values

Penicillium setosum, a member of the Penicillium section Lanata-divaricata, is known for its ability to produce high levels of patulin. However, there is a notable lack of information regarding the influence of environmental factors on the growth and patulin production in fruit juice of this species. In this study, we investigated the impacts of temperature (25, 30, 35, or 40 °C), initial pH value (3, 5, or 7), and incubation time (2, 4, or 6 days) on the growth and patulin production in pineapple juice of the selected P. setosum strain HR9-5. The modified Gompertz model was applied to estimate the maximum growth rate and lag time prior to growth. This strain had the highest growth rate with the shortest lag time within the temperature range 30–35 °C, with an initial pH range of 3–5. Furthermore, it had the greatest biomass dry weight and patulin production at 35 °C with an initial pH of 3, and at 25 °C with an initial pH of 7, respectively. The growth rate and lag time prior to growth of P. setosum HR9-5 were significantly influenced by the initial pH, whereas the biomass dry weight was strongly affected by temperature and incubation time. Additionally, all factors and their interactions had a significant impact on patulin production. This study provided the first report on the effect of environmental factors on growth and patulin production by P. setosum in pineapple juice. These findings can contribute to formulating effective prevention strategies to control the growth of P. setosum and subsequent patulin production in pineapple and other fruit juices.

Modeling the Role in pH on Contaminant Sequestration by Zerovalent Metals: Chromate Reduction by Zerovalent Magnesium.

The role of pH in sequestration of Cr(VI) by zerovalent magnesium (ZVMg) was characterized by global fitting of a kinetic model to time-series data from unbuffered batch experiments with varying initial pH values. At initial pH values ranging from 2.0 to 6.8, ZVMg (0.5 g/L) completely reduced Cr(VI) (18.1 μM) within 24 h, during which time pH rapidly increased to a plateau value of ∼10. Time-series correlation analysis of the pH and aqueous Cr(VI), Cr(III), and Mg(II) concentration data suggested that these conditions are controlled by combinations of reactions (involving Mg0 oxidative dissolution and Cr(VI) sequestration) that evolve over the time course of each experiment. Since this is also likely to occur during any engineering applications of ZVMg for remediation, we developed a kinetic model for dynamic pH changes coupled with ZVMg corrosion processes. Using this model, the synchronous changes in Cr(VI) and Mg(II) concentrations were fully predicted based on the Langmuir-Hinshelwood kinetics and transition-state theory, respectively. The reactivity of ZVMg was different in two pH regimes that were pH-dependent at pH < 4 and pH-independent at the higher pH. This contrasting pH effect could be ascribed to the shift of the primary oxidant of ZVMg from H+ to H2O at the lower and higher pH regimes, respectively.

Efficacy and mechanism of copper removal from electroplating wastewater by schwertmannite-like mineral

To explore the key influencing factors of copper removal by schwertmannite-like mineral and its mechanism of action, a shake flask method was used to synthesize schwertmannite-like mineral by adding Na2SiO3 and CaCl2 in the synthesis process of schwertmannite. The results showed that increasing the initial pH value from 2.0 to 5.0 increased the copper removal rate by 30.18%, indicating that high pH value effectively promoted copper removal. However, increasing the complexing agent concentration from 0.7 to 1.5 mmol/L decreased the copper removal rate by 27.51%, implying that high complexing agent concentration significantly inhibited copper removal. At a temperature of 40 °C, pH of 5.0, coexisting ion concentration (Mg2+, K+, Na+) of 1.5 mmol/L, complexing agent concentration (EDTA-Na2) of 0.5 mmol/L, and copper content of 50 mg/L, the removal of copper was achieved with the addition of 0.5 g/L FeSO4·7 H2O, 1.01 mL/L H2O2, 0.58 g/L Na2SiO3, and 3.25 g/L CaCl2. Under these conditions, the removal of copper reached the highest level of 97.99%, which was 85.01% higher than that of schwertmannite. When the schwertmannite-like mineral was dissolved in 1 L of ultrapure water, the highest copper dissolving rate was 1.98%, which was 19.06% less than that of schwertmannite. Due to the synergy of several mechanisms, including adsorption and CaSiO3 co-precipitation, the schwertmannite-like mineral has better removal efficiency and stability than schwertmannite.

Process Optimization and Equilibrium, Thermodynamic, and Kinetic Modeling of Toxic Congo Red Dye Adsorption from Aqueous Solutions Using a Copper Ferrite Nanocomposite Adsorbent.

In the present investigation of copper ferrite, a CuFe2O4 nanocomposite adsorbent was synthesized using the sol-gel method, and its relevance in the adsorptive elimination of the toxic Congo red (CR) aqueous phase was examined. A variety of structural methods were used to analyze the CuFe2O4 nanocomposite; the as-synthesized nanocomposite had agglomerated clusters with a porous, irregular, rough surface that could be seen using FE-SEM, and it also contained carbon (23.47%), oxygen (44.31%), copper (10.21%), and iron (22.01%) in its elemental composition by weight. Experiments were designed to achieve the most optimized system through the utilization of a central composite design (CCD). The highest uptake of CR dye at equilibrium occurred when the initial pH value was 5.5, the adsorbate concentration was 125 mg/L, and the adsorbent dosage was 3.5 g/L. Kinetic studies were conducted, and they showed that the adsorption process followed a pseudo-second-order (PSO) model (regression coefficient, R2 = 0.9998), suggesting a chemisorption mechanism, and the overall reaction rate was governed by both the film and pore diffusion of adsorbate molecules. The process through which dye molecules were taken up onto the particle surface revealed interactions involving electrostatic forces, hydrogen bonding, and pore filling. According to isotherm studies, the equilibrium data exhibited strong agreement with the Langmuir model (R2 = 0.9989), demonstrating a maximum monolayer adsorption capacity (qmax) of 64.72 mg/g at pH 6 and 302 K. Considering the obtained negative ΔG and positive ΔHads and ΔSads values across all tested temperatures in the thermodynamic investigations, it was confirmed that the adsorption process was characterized as endothermic, spontaneous, and feasible, with an increased level of randomness. The CuFe2O4 adsorbent developed in this study is anticipated to find extensive application in effluent treatment, owing to its excellent reusability and remarkable capability to effectively remove CR in comparison to other adsorbents.

Heterologous expression of the novel dimeric antimicrobial peptide LIG in Pichia pastoris

The antimicrobial peptide (AMP) LI is a fusion product of antimicrobial peptide LL37 produced by human neutrophils and Indolicidin secreted by bovine neutrophils. LI retained the antimicrobial activity of the parental peptides and showed high cell selectivity. In this study, the flexible linker Gly-Ser-Gly (G-S-G) was used to ligate LI into dimeric LIG, and constructed the Pichia pastoris (P. pastoris) expression vector pPIC9K-6×His-3×FLAG-LIG. The total protein expression of P. pastoris GS115 reached the highest level (189.6 mg/L) after 96 h induction with 3 % methanol at the initial pH value of 7.0. Finally, 5.9 mg/L of recombinant LIG (rLIG) was obtained after enterokinase digestion and purification. The rLIG had high antimicrobial activity and low hemolytic activity. Compared with monomer LI, GSG linked dimeric LIG, which had no significant change in antimicrobial activity and had good salt ions stability. In this study, the dimeric antimicrobial peptide LIG was successfully expressed, which provided a new idea for the expression of AMPs in the P. pastoris expression system, and had important significance for the application of AMPs.

Initial solution pH value for the construction of a 3D hydroxyapatite via the trisodium citrate-assisted hydrothermal route.

In this study, a trisodium citrate (TSC)-assisted hydrothermal method is utilized to prepare three-dimensional hydroxyapatite (3D HA). Understanding the role of TSC in the preparation of 3D HA crystals may provide valuable methods to design advanced biomaterials. As one of the indexes of solution supersaturation, the initial pH (ipH) value can not only directly affect the nucleation rate, but also affect the growth of HA crystals. In this work, the effect of the ipH on the microstructure, particle size distribution, and specific surface area of the 3D HA is explored. Results showed that the morphology of 3D HA transformed from a bundle to a dumbbell ball and then a dumbbell with an increase in the ipH. A corresponding mechanism of such a structural evolution was proposed, providing inspiration for the fabrication of innovative 3D HA structures with enhanced biological functionality and performance.

Cost-effective method of simultaneous removal of copper and phosphate on environmentally friendly nanomaterial

Environmentally friendly and economically viable methods are essential in the selection of materials and techniques for the synthesis of nano- -zero-valent iron. Plants, with their high polyphenol content and antioxidant capacity, have found application in eco-friendly synthesis processes. The defi-nitive screening design (DSD) monitored four key process parameters for the concurrent removal of copper and phosphate: copper concentration (ranging from 1 to 9 mg L-1), phosphate concentration (ranging from 1 to 9 mg L-1), initial pH values (ranging from 2 to 10), and the dosage of nano-zero-valent iron (ranging from 2 to 16 mL). The analysis results provide valuable insights into the significant individual factors influencing the process, along with the potential for their interactions. The model also proposes process optimization to attain maximum removal efficiency, and subsequent verification confirmed its superiority among the alternatives. Mechanisms such as sorption, reduction, complexation, electrostatic attraction, and ligand exchange play pivotal roles in the effective removal of copper and phosphate using nano-zero-valent iron. In summary, this research yields several benefits: the utilization of environment-ally sustainable materials, a substantial reduction in experimental complexity, coupled with the ease of the entire procedure, simultaneous and highly efficient copper and phosphate removal, favorable pH levels and, notably, no require-ment for additional treatment.

Removal of Crystal Violet Dye by Electrocoagulation – Analysis of Electrode and Solution Changes

This study investigates the changes at the electrodes and in the solution during crystal violet dye removal by electrocoagulation at different current densities (0.016, 0.024, and 0.032 A cm&amp;lt;sup&amp;gt;–2&amp;lt;/sup&amp;gt;) and initial pH values (3.2, 5.5, and 7.0). The electrocoagulation process, which lasted 50 min, revealed changes in pH, temperature, electrical conductivity, and concentration of the crystal violet dye in the solution. The results demonstrate complete removal of crystal violet dye at the highest current density (achieved after 40 min) and an initial pH of 5.5 (complete removal after 30 min). During the electrocoagulation process, both the anodic and cathodic electrode materials were consumed. The consumption of electrode material increased with higher current density and solution pH, the influence of current density being more pronounced. Examination of the electrode surfaces under a light microscope revealed that the anodes dissolved uniformly and locally during the electrocoagulation process, while the cathodes mostly underwent uniform corrosion.

Reaction of organic phosphates with oxides: Effects on pH, the equation used to describe the reaction, and on desorption

AbstractOrganic phosphates are an important component of soil phosphate reserves. We studied the sorption of three organic phosphates by goethite and by aluminium oxide and compared them with the sorption of inorganic phosphate (Pi). The organic phosphates were inositol hexa‐phosphate (IHP), glycerol phosphate (GlyP), and glucose‐6‐phosphate (G6P). We used five different initial pH values and 10 different initial concentrations. We measured both sorption and desorption. We used an equation which we call the Sibbesen‐Langmuir equation to successfully describe the observations over a 10,000 fold concentration range. Sorption increased the pH. The effects were largest at low pH and low initial concentration and were in the sequence Pi &gt; IHP &gt; G6P &gt; GlyP. This sequence was a consequence of differences in ion size and mean charge. The different feedback effects of the different ions affected the shape of plots of sorption against concentration; similarity to the Langmuir shape was in the opposite sequence. Desorption curves always fell to the left of sorption curves; that is, there was always hysteresis. Part of this was an experimental artefact because desorption was measured at lower pH than sorption, but we provide evidence that this caused only part of the effect. The effects were greatest for Pi and least for IHP. We think that this hysteresis occurs because the adsorbed molecules diffuse into faults in the reacting medium. This would be more difficult for organic phosphate than for inorganic phosphate. Although hysteresis was smaller for organic phosphates, it was nevertheless substantial. We suggest that this is an important factor in their stability in soils.

Chemical and physical properties of radiopaque Portland cement formulation with reduced particle size.

This study compared the chemical and physical properties of an experimental radiopaque white Portland cement (REPC) with reduced particle size to ProRoot white mineral trioxide aggregate (WMTA). The particle size distribution of experimental Portland cement (EPC) was examined, and then nano-zirconium oxide (nano-ZrO) was added to produce REPC. Chemical analysis, initial setting time, pH values, and push-out bond strength were evaluated. Results showed that REPC had smallest particle size (354.5±26.45 nm), while PC had the largest (1,309.67±60.54 nm) (p<0.05). Differences in chemical composition were observed. REPC exhibited shorter setting time (32.7±0.58 min) compared to WMTA (131.67±2.89 min) and PC (163.33±2.89 min) (p<0.05). All groups showed alkaline pH (p<0.05). REPC demonstrated the highest push-out bond strength (22.24±4.33 MPa) compared with WMTA (15.53±3.26 MPa) and PC (16.8±5.43 MPa) (p<0.05). This cost-effective PC formulation reduced the setting time and increased the push-out bond strength while maintaining the alkaline properties of the original cements.

Renewable-based treatment solution of Reactive Blue 21 dye on fly ash as low-cost and sustainable adsorbent

This study investigated the removal of Reactive Blue 21 (RB 21) dye from aqueous solutions by adsorption, evaluating the waste fly ash (FA). The effects of the parameters, such as initial dye concentration (100–750 mg/L), initial pH (2.0–8.0), adsorbent dose (1.0–4.0 g/L), and temperature (298–323 K) on the adsorption process were investigated. The optimum initial pH value was 2.0 for the highest RB21 dye removal (75.2 mg/g). At optimized conditions (pH 2.0, an adsorbent dosage of 1.0 g/L, a dye concentration of 750 mg/L, and an equilibrium time of 72 h), the highest adsorption capacity was found to be 105.2 mg/g. Moreover, the results of the kinetic studies fitted the pseudo-second-order kinetic model. Equilibrium data were best represented by the Langmuir isotherm model, with a maximum monolayer adsorption capacity of 103.41 mg/g at 323 K. ΔGads0 values were negative and varied from 11.64 to 9.50 kJ/mol in the temperature range of 298–323 K, the values of enthalpy (ΔHadso) and entropy (ΔSadso) of thermodynamics parameters were calculated as 37.62 kJ/mol and 86.67 J/mol K, respectively, indicating that this process was endothermic. Furthermore, the adsorbent costs for powdered activated carbon (PAC) and FA to remove 1 kg of RB 21 dye from aqueous solutions are calculated as 2.52 U.S. $ and 0.34 U.S. $, respectively. It is seen that the cost of FA is approximately 7.4 times lower than PAC. The results showed that FA, a low-cost industrial waste, was promising for the adsorption of RB 21 from aqueous solutions.

Investigation of the preparation pH value influence on the single step silica Aerogel monolith porosity

The influence of acidic and basic environment of sol on the final Aerogel properties was studied in this work. Transparency of silica Aerogel monolith was investigated according to their initial preparation pH values. The findings show that silica Aerogels’ optical transmittance is highly sensitive to the pH values employed in their production. Specifically, the silica Aerogels prepared at a pH of 8 demonstrate the highest level of transmittance. SEM as well as BET measurements of silica Aerogels are employed as pore structure probes to ascertain the changes, that occur in a TEOS precursor silica gel, as a function of the variation of the initial preparation pH value. There is a systematic correlation between sol acidic/ basic environment variation and Aerogel surface area except around pH 2 which exhibits abnormal results. While the relation between porosity as well as pore size and preparation pH values were more irregular.