Sodium Metasilicate Pentahydrate Research Articles

Utilization of waste glass as precursor material in one-part alkali-activated aggregates

The increasing demand for glass products has led to a rise in waste glass (WG), which is commonly disposed of in landfills, causing environmental degradation. Moreover, the direct adoption of a high volume of WG as aggregates in concrete can lead to unfavorable ASR expansion due to its high level of reactive silica. This study explores a one-part alkali activation method to produce WG-based aggregates, aiming to reduce the reactive silica content, mitigate ASR expansion and increase the recycling rate of WG. Waste glass powder (WGP) with a replacement ratio of 100% was combined with two different alkalis (sodium metasilicate pentahydrate (Na2SiO3.5H2O) and sodium aluminate (NaAlO2)) through the cold-bonded one-part alkali activation method to produce WG-based alkali-activated aggregates (WG-AAAs). The influence of various activator contents (0%, 6%, 9%, 12% and 15%) on the physical and mechanical properties of the WG-AAAs was investigated. The WG-AAAs had a bulk density ranging from 920 to 1010 kg/m3, which can be classified as lightweight aggregates. The WG-AAAs with 12% NaAlO2 showed the best performance, with a water absorption of 8.46% and single particle crushing strength of 3.19 MPa. SEM-EDS and XRD results indicated that WG-AAAs with the supply of alumina from NaAlO2 exhibited a lower Si/Al ratio, leading to the formation of C-(N)-A-S-H gel, which improved the strength and creating a denser microstructure. Furthermore, the WG-AAAs showed no ASR expansion concerns, conforming to the expansion limit specified in ASTM C1260.

Sodium metasilicate-activated one-part geopolymer concrete: Impact strength assessment with bottom ash substitution and fiber reinforcement

This study aims to investigate the effect of fibers on the impact strength of fibrous one-part geopolymer concrete (OPGC) to mitigate its brittleness. This research examines the impact strength of OPGC activated with sodium metasilicate pentahydrate, utilizing fly ash as a precursor material. The study uniquely explores the effects of bottom ash, substituted at varying levels (25 % to 100 %) for sand, within the OGPC matrix. Additionally, incorporating two distinct fiber types, polypropylene and kenaf, individually at 0.5 % and in a hybrid combination at 0.25 % each, offers a fresh perspective on fiber reinforcement in OGPC. Scanning electron microscopy and X-ray diffraction provide critical insights into the microstructural and mineralogical properties of the developed OPGC. The impact strength of OPGC with this specific combination of materials has not been previously investigated by any researchers, establishing the novelty of this study. Results revealed that the combination of fibers with 25 % BA exhibited a synergistic effect, leading to a notable enhancement in impact strength. Conversely, the impact strength declined with other combinations of materials. Polypropylene fibers demonstrated the highest performance in terms of impact strength for OPGC, followed by the hybrid fiber combination, with kenaf fibers exhibiting the lowest performance in this regard.

Influence of elevated temperatures on the mechanical behavior of one-part coal ash geopolymer concrete with sodium metasilicate pentahydrate and sodium metasilicate anhydrous as alkaline activators

Geopolymers can be synthesized through either a one-part or two-part combination methodology. The aluminosilicate precursor is blended with an alkaline activator solution in the two-part mixture. Conversely, the one-part mixture technique incorporates water directly into the dry composite comprising the aluminosilicate precursor and solid activator. Using one-part geopolymer concrete (OPGC) stands out as a beacon of sustainability, presenting a compelling alternative to conventional cement concrete in construction projects. A noticeable gap exists in the extant literature on investigations on the response of OPGC when subjected to elevated temperatures. The study aims to evaluate the effect of elevated temperatures on the mechanical behavior of OPGC. Sodium metasilicate pentahydrate (SMP) and sodium metasilicate anhydrous (SMA) are the two types of one-part alkaline activators used to make OPGC. Fly ash was applied as a precursor, and bottom ash was varied from 25 % to 100 % as a substitute for sand in the mix designs of the OPGC specimens. The concrete specimens were characterized by their workability, compressive strength, microstructures, mineralogical properties, and thermal stability. The results revealed that OPGC specimens with SMP and SMA activators containing bottom ash, exposed to 100 °C, exhibited increased compressive strength by 7.31 % and 39.09 %, respectively, compared to those exposed to 30 °C. This trend persisted, with the highest enhancements observed at 200 °C, reaching 37.62 % and 72.39 % for SMP and SMA, respectively. However, compressive strength declined at higher temperatures, with the most significant drop occurring at 800 °C. X-ray Diffraction results and microstructural analysis confirmed that the optimized geopolymer concrete is characterized by a binding product in Sodium Aluminosilicate Hydrate (N-A-S-H) gels, forming a robust three-dimensional geopolymer network. This behaviour implies a high level of toughness for the optimized geopolymer concrete. The study underscored the importance of comprehending the bonding mechanism of geopolymer concrete activated with SMP and SMA against high temperatures, as it clarifies the scientific underpinnings of its thermal resilience and resistance to deterioration, thus guiding the advancement of durable and eco-friendly construction materials.

On the role of alkali content on one-part alkali activated slag pastes produced with tri- blend solid activators

The paper investigates the effect of tri-blend solid alkaline activators, based on sodium metasilicate pentahydrate, potassium hydroxide and sodium carbonate, on the physico-chemical features, the fresh and hardened performances of activated slag pastes prepared with the one-part methodology. Specifically, the alkali to slag ratio (Ac) and the total amount of the selected activators were varied at a fixed water/binder ratio, molar silica modulus (Ms) and relative mass activators ratio. Microstructures and reaction products were analyzed by means of X-ray diffraction, thermogravimetry, scanning electron microscopy and FT-IR. Fresh and elasto-mechanical properties of pastes were also evaluated. Amorphous calcium carbonate (ACC) as well as metastable vaterite were found in low reacted systems, produced by the preferential early-age reaction between dissolved carbonate ions present in the pore solution and the calcium ions released by the partial dissolution of the slag and stabilized by a sufficient high concentration of magnesium in the pore solution, not consumed to the form hydrotalcite. Sodium carbonate failed in extending the pot life of the investigated systems. The optimal alkali content was found to be close to 0.075 as it determines the development of compact and dense microstructure (2025 kg/m3), the maximum elasto-mechanical properties (elastic modulus of 26.1 GPa and compressive strength of 102.8 MPa at 28 days) and it allows to produce flowable mixtures (200 mm).

Use of sodium metasilicate as silica source and stabilizing agent in two-part metakaolin–H2O2 geopolymer foams

The synergistic effects of the SiO2/Al2O3 ratio (2.0, 2.5, and 3.0) and H2O2 content (1.5%, 3.0%, and 6.0%) were evaluated in metakaolin-based geopolymer foams using sodium metasilicate pentahydrate as a complementary silica source. Sodium metasilicate helped to stabilize the pores in foams with SiO2/Al2O3 molar ratios of up to 2.5 cured at 50 °C without stabilizing additives. The optimum porous system for insulation cores was obtained using a SiO2/Al2O3 ratio of 2.5 and H2O2 content of 6%. Furthermore, a SiO2/Al2O3 molar ratio of 3.0 reduced pore formation as the increased geopolymerization and viscosity served as a barrier to bubble diffusion.

Metasilicate-based alkaline mineral water confers diarrhea resistance in maternally separated piglets via the microbiota-gut interaction

Stress or stress-induced intestinal disturbances, especially diarrhea, are the main triggers for inflammatory bowel disease and irritable bowel syndrome. Diarrhea and intestinal inflammatory disease afflict patients around the world, and it has become a huge burden on the global health care system. Drinking sodium metasilicate-based alkaline mineral water (SM-based AMW) exerts a potential therapeutic effect in gastrointestinal disorders, including gut inflammation, and diarrhea, but the supportive evidence on animal studies and mechanism involved remain unreported. The maternally separated (MS) piglet (Newly weaned piglet) is an excellent model to investigate the treatment of diarrhea in infant. This study aims to determine whether drinking SM-based AMW confers diarrhea resistance in maternally separated (MS) piglets under weaning stress and what the underlying mechanisms are involved. 240 newly weaned piglets were randomly divided into the Control group and the sodium metasilicate pentahydrate (SMP) group. A decreased diarrhea incidence was observed in SMP treatment piglets. The intestine injury and activated stress hormones (COR and ACTH) induced by weaning was alleviated by SM-based AMW. This may be related to the improvement of intestinal microflora structure and function by SMP, especially the increase of s_copri abundance. Meanwhile, SMP maintained the integrity of the duodenal mucus barrier in MS piglets. Importantly, by targeting NF-κB inhibition via the microbiota-gut interaction, SM-based AMW alleviated intestinal inflammation, maintained fluid homeostasis by modulating aquaporins and fluid transporter expression, and enhanced barrier integrity by suppressing MLCK/p-MLC signaling. Therefore, drinking metasilicate-based alkaline mineral water confers diarrhea resistance in MS piglets via the microbiota-gut interaction.

EFFECT OF ADDITIONAL INPUT OF Na3PO4∙12H2O ON ACID RESISTANCE INDICATORS OF HYBRID ALKALINE CEMENTS

This work is devoted to the study of the direct influence of phosphate salt, using theexample of trisodium phosphate (Na3PO4∙12H2O), on the acid resistance index of hybrid alkaliactivated cements. After all, acid resistance is becoming an increasingly important property for cement materials due to a wide range of applications where they are exposed to aggressive acid environments, especially in the chemical and foodindustries. In addition to the above, these include sewage systems, agricultural environments, oilwells, acid rain, and much more.Conventional Portland cement binders are known to be sensitive to acid attack due to thechemical nature of their main hydrated phases.Binders activated by alkali are an alternative to traditional Portland cement and are characterized bya number of special properties, especially if appropriate modifications are made to the component compositions of these cements. One of the main properties characteristic of alkali-activated binders is their resistance to the influence of aggressive environments.Based on the literature analysis and taking into account the domestic and world assets in this direction, a number of model systems were developed based on blast furnace granulated slag and an alkaline component using phosphate salt with different percentages. Thus, the object of the research is the slag-alkaline system "furnacegranulated slag - alkaline component (represented by sodium metasilicate pentahydrate) - trisodiumphosphate". In the course of research, the main physical and mechanical characteristics of thedeveloped compounds were determined and the results were analyzed. Determination of the acidresistance index (Ks≥0.8) confirmed the feasibility of using Na3PO4∙12H2O in the production of acidresistant alkali-activated cements.

A Study on the Influence of Sodium Silicate Concentration and SiO2 : Na2O Ratio on the Properties of Low-Calcium Fly Ash-Based Alkali-Activated Materials Cured at Ambient Condition

Low-calcium Fly ash-based alkali-activated materials (AAM) have some extraordinary properties such as high fire resistance and low shrinkage. However, they have lower strength and high setting time when curing at ambient temperature conditions. Therefore, this research aimed to improve the strength and setting time of low-calcium fly ash-based AAM curing at ambient temperature conditions. The effect of the changes in concentration and modulus of sodium silicate and curing condition of the materials were studied on the properties of the AAM. Fly ash type II, 32% sodium metasilicate pentahydrate, 32 and 56% sodium disilicate solution, 8M sodium hydroxide, and standardized were used. Using 32% sodium disilicate solution significantly improved the flowability of mortar. Moreover, it increased the compressive strength and remarkably decreased the setting time of AAM at ambient temperature curing. The decrease in the concentration of sodium disilicate has a significant influence on the reactivity of fly ash.

A consideration on the one-part mixing method of alkali-activated material: problems of sodium silicate solubility and quick setting

This research investigates the properties of alkali-activated materials (AAMs) using sodium metasilicate, with the ratio of SiO2:Na2O equals 1. This study was conducted to achieve the following three aims. Firstly, to understand the solubility mechanism of granular sodium metasilicate pentahydrate (Na2SiO3.5H2O) when used in a one-part mixing method. Secondly, to investigate the properties of AAMs when a sodium metasilicate aqueous solution is used as an alkaline material and as a source of silica. Lastly, to study the retardation effect of sucrose on AAMs. This research used aluminum silicate precursors, such as low-calcium fly ash, slag, and micros silica, alkali activators, such as NaOH pellets and Na2SiO3.5H2O, and standardized sand. The alkaline activators were first dissolved in water using a water bath shaker to achieve the alkaline solution. Sucrose, which is about 2% of the weight of the solid precursors, was added to modify the reaction process between the precursors and the alkaline materials. Four types of samples were prepared: M1, M2, M3, and M4, with the fly ash, slag, and silica fume ratios of 80:20:0, 70:30:0, 75:20:5, and 100:0:0, respectively. The research conducted solubility test of the alkaline materials, flowability, 7-, 28-, 56-day compressive and flexural tests, drying shrinkage test of mortar samples, and the setting tests of pastes with and without sucrose. The results show that the dissolution time of the NaOH was much shorter, whereas Na2SiO3.5H2O needed a solvent with a temperature of around 40 °C to be fully dissolved. This problem of solubility decreases the quality of AAMs formed using the one-part mixing method. Among the mortar samples, the M4 had the highest flow rate, while M3 had the lowest flow rate. M2 had the highest compressive and flexural strength of 43.4 MPa and 6.1 MPa, respectively. The setting time test shows that sucrose retards the reaction process in AAM.

Silicate and Hydroxide Concentration Influencing the Properties of Composite Al2O3-TiO2 PEO Coatings on AA7075 Alloy

This work evaluates the effect of sodium meta-silicate pentahydrate (SMS) and potassium hydroxide concentrations on properties of Al2O3-TiO2 coatings produced through plasma electrolytic oxidation in a solution containing 3 g L−1 potassium titanyl oxalate, (PTO), using a unipolar waveform with constant current density. The surface and cross-section characteristics of PEO coatings including morphology, elemental distribution, and phase composition were evaluated using FESEM, EDS, and XRD techniques. Voltage-time response indicated the concentration of SMS and KOH had a significant effect on the duration of each stage of the PEO process. More cracks and pores were formed at the higher concentrated solutions that resulted in the incorporation of solution components especially Si into the coating inner parts. Ti is distributed throughout the coatings, but it had a dominant distribution in the Si-rich areas. The coating prepared in the electrolyte containing no silicate consisted of non-stoichiometric γ-Al2O3 and/or amorphous Al2O3 phase. Adding silicate into the coating electrolyte resulted in the appearance of α-Al2O3 besides the dominant phase of γ-Al2O3. The corrosion behaviour of the coatings was investigated using the EIS technique. It was found that the coating prepared in the presence of 3 g L−1 SMS and 2 g L−1 KOH, possessed the highest barrier resistance (~10 MΩ cm2), owing to a more compact outer layer, thicker inner layer along with appropriate dielectric property because this layer lacks the Si element. It was discovered that the incorporation of Ti4+ and especially Si4+ in the coating makes the dielectric loss in the coating.

Basic Properties of fly Ash/Slag -Concrete Slurry Waste Geopolymer Activated by Sodium Carbonate and Different Silicon Sources

As a kind of granular waste with complex composition and alkali corrosiveness, concrete slurry waste (CSW) has severe recycling limitations in the ordinary Portland cement (OPC). Considering this, a new type of geopolymer, prepared by granulated blast furnace slag/fly ash, concrete slurry waste, and powdered activators (sodium carbonate and different silicon sources including sodium metasilicate pentahydrate and silica fume), was adopted to conduct a comparative study with the OPC counterpart. In this study, the homogenized CSW was mixed in the OPC and geopolymer with a constant ratio of 50 wt%, respectively. Then the properties were studied in terms of the flowability, setting times, mechanical strengths, and microstructures. The results showed that better flowability (200 mm) could be achieved in the obtained geopolymer than in the OPC reference group (95 mm) by increasing the powdered activators. The setting time of the OPC was significantly shortened due to the addition of CSW. The strengths of geopolymer were supported by the produced C-A-S-H and carbonates, with less chemically bonded water than the hydration products in the reference group. The dominant size of pores in the hardened geopolymer was much smaller than that in the OPC group which was 80 nm. Silica fume could be the alternate of the sodium metasilicate pentahydrate and had an insignificant negative impact on the fresh and hardened properties and microstructures of the geopolymer when the incorporation rate was within 5%.

Facile synthesis and characterisation of novel Sn/Si mixtures for the efficient removal of methylene blue and crystal violet dyes from aqueous media

ABSTRACT In this work, novel mixtures based on silicon and tin materials were synthesised via reaction of 2.407, 5.247, 7.195, or 9.59 g of tin chloride dihydrate with 6 g of sodium metasilicate pentahydrate. The samples, which were synthesised using 2.407, 5.247, 7.195, and 9.59 g, are abbreviated as T1, T2, T3, and T4, respectively. XRD confirmed that these mixtures consist of amorphous Sn/Si, sodium tin silicate, tin oxide, and sodium silicate. The average crystallite size of T1, T2, T3, and T4 samples is 5.23, 8.13, 12.26, 15.72 nm, respectively. The synthesised mixtures were used as adsorbents for the removal of methylene blue and crystal violet dyes from aqueous media. 15 min, pH 6, and 298 Kelvin are regarded as the optimum conditions for the removal of studied dyes using T1, T2, T3, and T4 samples. The adsorption process of crystal violet or methylene blue dyes was fitted well with the Langmuir equilibrium isotherm and pseudo-second-order kinetic model. The thermodynamic parameters confirmed that the removal of crystal violet and methylene blue dyes is chemical, spontaneous, and exothermic. The maximum adsorption capacity of T1, T2, T3, and T4 samples towards crystal violet dye is 34.81, 36.83, 29.46, and 11.98 mg/g, respectively. Also, the maximum adsorption capacity of T1, T2, T3, and T4 samples towards methylene blue dye is 30.13, 29.33, 17.09, and 13.43 mg/g, respectively. HCl: butanol (1:3) can efficiently desorb the dyes for three cycles of adsorption/desorption. Hence, the adsorbents can be used successfully several times for the removal of crystal violet and methylene blue dyes.

Integrated corrosion‐resistant system for AZ31B Mg alloy via plasma electrolytic oxidation (PEO) and sol‐gel processes

AbstractIn this work, an integrated system that combines anodizing process with the deposition of a hybrid SiO2 sol‐gel coating was developed with the aim of improving the corrosion resistance of AZ31B Mg alloy. The optimization of the anodizing conditions using an alkaline electrolyte (NaOH) modified with different concentrations of sodium metasilicate pentahydrate was explored together with the preparation and deposition of a SiO2 sol obtained by hydrolysis and condensation of TEOS (tetraethoxysilane), GPTMS (3‐Glycidyloxypropyl) trimethoxysilane), colloidal SiO2 nanoparticles, and 1‐Methylimidazole (MI). The surface morphology, coating thickness, and composition were evaluated. The anodized coatings thickness was between 1.1 and 1.7 μm with composition corresponding to magnesium oxide and low silicon content. The corrosion performance was tested in 3.5% NaCl solution. The results revealed a good corrosion resistance behavior after the anodizing of the Mg alloys. However, the best corrosion resistance was reached when the porous PEO layer was sealed with a hybrid silica sol‐gel film. A decrease in the corrosion current density of three orders of magnitude is observed between Mg alloy (1.54E‐06 A/cm2) and multilayer system (2.80E‐8 A/cm2). Moreover, the polarization resistance for 8AF+SG samples showed a quite high value (31546.8 Ω cm2) compared to Mg alloy (207.3 Ω cm2).

Ultra-ductile behavior of fly ash-based engineered geopolymer composites with a tensile strain capacity up to 13.7%

This study introduces ultra-ductile fly ash-based engineered geopolymer composites (UD-EGCs). Four mixtures of UD-EGCs with different ratios of sodium metasilicate pentahydrate (SMP)-to-sodium hydroxide (SH) were designed and prepared at an identical water-to-binder ratio. Polyethylene (PE) fibers at 1.75 vol% were used as reinforcements. Experimental and analytical investigations of mechanical properties, micromechanical analysis, and chemical characterization of UD-EGCs were performed at both meso- and micro-scales. The UD-EGC mixtures were found to strain-harden with ultra-high ductility. Notably, the mixture using an SMP/SH ratio of 1.5 achieved a tensile strain capacity of 13.7% and a tensile strength of 6.8 MPa. Moreover, all mixtures were lightweight, with density below 1.83 g/cm3. From the chemical analysis, C-(N)-A-S-H and N-A-S-H were verified as the primary geopolymeric products of fly ash-based engineered geopolymer composites.

Protective effects of silicon and silicate salts against white rot disease of onion and garlic, caused by Stromatinia cepivora

This study aimed to determine the effect of silicon and silicate salts in reducing the incidence of white rot disease, caused by Stromatinia cepivora, on onion and garlic plants. Under greenhouse conditions silicon and silicate salts was used at 0.1, 0.2 and 0.3%. Before planting, onion transplants and/or garlic cloves were dipped for 1 h in the desired concentration. After planting, stem bases of plants were supplemented with the same concentration three times intervals at 30, 60 and 90 days after planting. Data showed that successful application resulted from silicon and silicate salts was obtained at 0.3%, which significantly reduced the incidence of white rot and improved the growth of onion and garlic plants. However, there were no significant differences between some treatments at 0.1, 0.2 and/or 0.3%. Field experiments were conducted in soils naturally infested with S. cepivora for 2 years to evaluate the effect of silicon and silicate salts at 0.3% on white rot incidence as well as the mechanisms underlying the observed of disease reduction. Application of silicon and silicate salts significantly reduced the incidence of white rot disease, increased the amount of chlorophyll a, chlorophyll b, carotenoids, proline and promoted the bulbs yield of onion and garlic plants. Potassium silicate solution (Ps) and sodium meta silicate pentahydrate (Ss) were more effective treatments. Calcium silicate was the least effective treatment. Application of silicon and silicate salts resulted in the increase of soil dehydrogenase enzyme and CO2 evolution in the rhizospheric soil of onion and garlic plants. Applications of silicon and silicate salts significantly stimulated systemic defense enzymes and enhanced the expressions of some genes into proteins in onion and garlic plants. These findings suggest that silicon and silicate salts reduced the incidence of white rot disease and exerts a beneficial effect on the field-grown garlic and onion plants, providing an alternative disease management strategy.

Experimental study of one-part geopolymer using different alkali sources

This paper investigates the feasibility of combining different solid alkali materials as activator to prepare one-part geopolymer mortars. The effects of different composite solid activators on aluminosilicate materials were studied and compared with the traditional water glass and sodium hydroxide composite solution activator through the measurement of fresh and harden properties and microstructural analysis. The results showed that sodium metasilicate pentahydrate was more suitable than quick-dissolving sodium silicate for preparation of geopolymer. The addition of sodium carbonate and calcium hydroxide in solid activator enhanced the compressive strength and decreased the setting time and flowability of the mixes. The highest compressive strength (47.4 MPa, 28 d) was obtained with the activators consisting of sodium metasilicate pentahydrate and sodium carbonate. While scanning electron microscope (SEM) analysis indicated that micro-pores left by the dissolution of metasilicate particles might have an adverse effect on the mechanical properties of mortar samples.

Mechanical and Corrosion Behavior of Plasma Electrolytic Oxidation Coatings on AZ31B Mg Alloy Reinforced with Multiwalled Carbon Nanotubes

Plasma electrolytic oxidation (PEO) is an effective surface modification technique. The PEO technique has been widely used to grow protective oxide layers into materials with lower corrosion resistance properties. In this study, a new technique was used for synthesizing AZ31B magnesium alloy reinforced with multiwalled carbon nanotubes (MWCNTs). After the synthesis, the composites were coated by PEO in a solution of sodium metasilicate pentahydrate (Na2SiO3·5H2O) and potassium hydroxide (KOH). The microstructure morphology and composition in the interface were characterized by scanning electron microscopy and energy-dispersive x-ray spectroscopy. The hardness, the elastic modulus and adherence of the coatings were studied by nanoindentation tests. Finally, the samples were subjected to corrosion tests by electrochemical impedance spectroscopy. The microstructure and mechanical analysis shows that the PEO coating morphology has a dependency on the MWCNTs content into the metal matrix and exhibited good mechanical properties and high corrosion resistance.

Development of high strength one-part geopolymer mortar using sodium metasilicate

In this study, the solid activator – the synthetic sodium metasilicate pentahydrate – was compared against water and a hybrid sodium silicate and sodium hydroxide activator solution. It was found that the solid activator outperformed the liquid activator as a part of water remained chemically bound to the undissolved particles, thus reducing the apparent water to binder ratio. Contrary to the liquid activator, the increase in activator content past a certain limit did not correspond to improvement in strength. Instead, the compressive strength reduced and the risk of efflorescence increased significantly. Scanning electron microscopy (SEM) analysis showed that the denser reaction products took up less volume and formed a shell as the remaining metasilicate particles gradually dissolved under moisture ingression. This would eventually develop into a void, and cause strength- and durability-related issues. Additionally, fly ash content, microsilica addition, particle size of the activator, binder content, water to binder content and curing condition also played an important role in the hardening and pore refinement of the mixes. The one-part synthesis method could improve the safety and efficiency in geopolymer production.

Application of Geopolymers Modified with Chitosan as Novel Composites for Efficient Removal of Hg(II), Cd(II), and Pb(II) Ions from Aqueous Media

In the present paper, two amorphous aluminum silicates (i.e. geopolymers) were synthesized via the interaction of 23.57 mmol of sodium metasilicate pentahydrate with 5.18 or 10.35 mmol of aluminum chloride hexahydrate. The synthesized geopolymers using 5.18 and 10.35 mmol of aluminum chloride hexahydrate were abbreviated as G1.25 and G2.50, respectively. Also, the synthesized geopolymers were modified with chitosan as novel composites. The synthesized composites using G1.25 and G2.50 were abbreviated as G1.25/Ch and G2.50/Ch, respectively. Besides, the synthesized geopolymers and their chitosan composites were characterized using different tools such as XRD, FT-IR, SEM, and EDX. Moreover, the synthesized geopolymers and their chitosan composites were utilized as efficient adsorbents for the removal of Hg(II), Cd(II), and Pb(II) ions from aqueous media. The Langmuir isotherm and pseudo-first-order kinetic model were more consistent with the removal of metal ions from aqueous media. Furthermore, the adsorption processes were spontaneous, exothermic, and chemisorption. In the case of Hg(II), the maximum adsorption capacity of G1.25, G2.50, G1.25/Ch, and G2.50/Ch were 131.93, 140.85, 166.67, and 173.91 mg/g, respectively. In the case of Cd(II), the maximum adsorption capacity of G1.25, G2.50, G1.25/Ch, and G2.50/Ch were 118.34, 134.95, 159.49, and 166.11 mg/g, respectively. In the case of Pb(II), the maximum adsorption capacity of G1.25, G2.50, G1.25/Ch, and G2.50/Ch were 102.15, 118.91, 128.21, and 156.01 mg/g, respectively.

Effect of Silicon and Phosphorus Additions and Their Interactions on Wheat Plants Grown on a Clay Soil

A pot experiment was conducted in clay soil collected from Agricultural Research Center farm, Giza governorate, Egypt. Wheat grains (Triticum aestivum L., Giza 168) were cultivated to study the effect of silicate and phosphate ions as well as their interactions on the growth and nutritional status of the growing plants, beside their availability in the studied soil. Silicon (Si) in the form of sodium meta-silicate penta-hydrate (Na2SiO3.5H2O) was added at a rate of 0, 200, 300 and 400 mg Si kg-1 soil, and phosphorus (P) in the form of calcium super phosphate was given at a rate of 0, 3.5, 7.0, 10.0 and 13.0 mg P kg-1 soil to represent 0, 25, 50, 75 and 100% of the recommended rate of P fertilization by the Egyptian Ministry of Agriculture for wheat cultivation. Also, the experiment included combinations between all these concentrations of Si and P. Obtained results showed that Si and P availability increased in the studied soil with increasing either Si or P concentrations added. This means that P availability in soil as an essential element for plant growth can be improved by addition of Si. Also, Si increased in plant with increasing applied Si concentrations. Interaction between Si and P generally increased all parameters of plant growth; such responses were significant for fresh and dry weights of wheat plants at booting stage. It could be recommended that selecting good P fertilization design, including time and rate of addition, goes along with values of available Si in the soil.