Simultaneous Removal of Pb2+ and Zn2+ Heavy Metals Using Fly Ash Na-X Zeolite and Its Carbon Na-X(C) Composite

The interactions between zeolite and two cellulose derivatives: A comprehensive analysis of liquid and solid phase properties

This study investigates the impact of cellulose-derived polymers, anionic carboxymethylcellulose (CMC), and cationic cellulose (CC) on the colloidal and thermal stability of zeolite Na-X materials. By exploring polymer adsorption onto Na-X surfaces and characterising the resultant materials, using FT-IR, XPS, SEM, PSD, CHN, and zeta potential, the research unveils how CMC and CC modify zeolite properties. This investigation elucidates the potential roles of these polymers in colloidal systems with zeolites, revealing their promise for crafting organic-inorganic materials. Additional insight was also provided by careful examination of the thermal stability (TGA-DSC) of the obtained cellulose/zeolite materials. Furthermore, the study distinguishes the different adsorption mechanisms of CMC and CC, with CMC relying on some weak interactions (H-bonding and van der Waals forces), while CC interacts mainly via electrostatic forces. Both CMC and CC can act as stabilizing agents, with CMC being more efficient and using both electrosteric and depletion stabilizations. Importantly, the concentration of CC plays a role in bridging flocculation, highlighting the concentration-dependent nature of the stabilization mechanism.

Molten Alkali-Assisted Formation of Silicate Gels and Its Application for Preparing Zeolites

Fly ash was used as raw material to prepare zeolites through silicate gels, assisted by the hydrothermal method. The silicate gels could be effectively formed in a few minutes in a molten alkali environment. The zeolites could be prepared by using these silicate gels through the hydrothermal method, which realizes the transformation from useless materials to highly valuable materials. The obtained zeolites were applied to the removal of ammonium in water, achieving the highvalue utilization of fly ash. The synthesized zeolites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrum (EDS), thermogravimetric (TG), and Fourier transform infrared (FTIR) spectroscopy. The study on the adsorption and removal of ammonium in water shows that the adsorption of ammonium is more in line with pseudo first-order kinetics, and the adsorption mainly occurs in the first 20 min. The adsorption can reach equilibrium in 30 min, and the maximum adsorption capacity can reach 49.1 mg/g. The adsorption capacity of ammonium has the best performance at pH = 5. Furthermore, within a certain range, an increase in temperature is beneficial for the removal of ammonium.

Potentials of mono- and multi-metal ion removal from water with cotton stalks and date palm stone residuals

In this work, cotton stalks (Gossypium barbadense) and date palm stones (Phoenix dactylifera) have been used as biosorbents to remove cadmium; Cd(II), lead; Pb(II), and zinc; Zn(II) from mono- and multi-solutions. Each biosorbent was characterized using SEM-EDX, and FT-IR. The findings showed that pH, dose, contact time, metal concentration, and particle size affect the treatment process. The adsorption pattern was Pb(II) > Cd(II) > Zn(II) for both biosorbents. The adsorption performance of cotton stalks was higher than that of date palm stones. The fitted maximum uptake capacities; qm of cotton stalks were higher than those of date palm stones. The maximum adsorption at optimum conditions of Pb(II), Cd(II), and Zn(II) with cotton stalks were 98%, 92.1%, and 78.9%, respectively, within 30 min. While the maximum adsorption of Pb(II), Cd(II), and Zn(II) with date palm stones were 94.6%, 76%, and 68.6%, respectively. Results confirmed the antagonistic effect of heavy metal removal at optimum conditions. Biosorbents could remove ~ 100% of the metal ions from real wastewater samples. Regeneration investigation revealed a successful reusability of both biosorbents for four cycles.

Restoration of soils contaminated with PAHs by the mixture of zeolite composites mixed with exogenous organic matter and mineral salts

The major cause of soil degradation (contamination, erosion, compaction) is closely linked to agriculture, i.e., unsustainable agriculture practices, which are reflected in the depletion of the soil organic carbon pool, loss in soil biodiversity, and reduction of C sink capacity in soils. Therefore, the agricultural practice of applying carbon-rich materials into the soil is an attractive solution for climate change mitigation and soil ecosystem sustainability. The paper aimed to evaluate the effectiveness of the addition of organic-mineral mixtures to the mineral salts (NPK), including the exogenous organic matter (lignite) mixed with zeolite-carbon (NaX-C) or zeolite-vermiculite (NaX-Ver) composites in the restoration of soils contaminated with PAHs. The addition of zeolite composites to fertilizer resulted in a significant reduction in soil PAH levels and a corresponding reduction in plant tissue content, without compromising yields, compared to the control and separate application of NPK. A Significant correlation between PAHs and pHH2O, pHKCl, EC and dehydrogenase activity (DhA) was found in soils. The addition of zeolite composites with lignite significantly reduced the content of PAHs in straws, especially following the application of NaX-C. However, in the case of grains, the highest percentage reduction in comparison to NPK was observed for the highest dose of NaX-Ver.

Fly Ash-Based Na-X Zeolite Application in Separation Process of Bovine Serum Albumin from Aqueous Solution in the Presence of Organic Substances with Anionic Character

The main purpose of the investigations was to explore the protein adsorption on porous materials, as well as to identify the mechanisms of protein attachment without and with other common environmental contaminants, such as drugs, polymers or surfactants. This study applied the Na-X zeolite for the adsorption of bovine serum albumin (BSA) from solutions with various pH values. Electrophoretic mobility measurements and potentiometric titrations were conducted in systems containing both protein and/or PAA (poly(acrylic acid) polymer/DCF (diclofenac) drug/SDS (sodium dodecyl sulfate) surfactant to investigate the protein binding mechanisms in the complex adsorbate systems. In addition, aggregate size and stability measurements were performed in the investigated systems. Based on the research results, it was possible to conclude that the protein adsorbed most preferably on the zeolite surface at a pH value close to its isoelectric point (pI) (102.15 mg/g), and protein adsorption was the lowest in the solutions with strongly alkaline (29.61 mg/g) or acidic (77.45 mg/g) pH values. Thus, the examined zeolitic material can be considered an effective adsorbent for protein removal from an aqueous solution.

Zeolite Composite Materials from Fly Ash: An Assessment of Physicochemical and Adsorption Properties

Waste fly ash, with both low (with the addition of vermiculite) and high contents of unburned coal, were subjected to hydrothermal syntheses aiming to obtain zeolite composite materials-zeolite + vermiculite (NaX-Ver) and zeolite + unburned carbon (NaX-C). The composites were compared with parent zeolite obtained from waste fly ash with a low content of unburned carbon (NaX-FA). In this study, the physicochemical characteristics of the obtained materials were evaluated. The potential application of the investigated zeolites for the adsorption of ammonium ions from aqueous solutions was determined. Composite NaX-Ver and parent zeolite NaX-FA were characterized by comparable adsorption capacities toward ammonium ions of 38.46 and 40.00 mg (NH₄⁺) g^-1, respectively. The nearly 2-fold lower adsorption capacity of composite NaX-C (21.05 mg (NH₄⁺) g^-1) was probably a result of the lower availability of ion exchange sites within the material. Adsorbents were also regenerated using 1 M NaCl solution at a pH of 10 and subjected to 3 cycles of adsorption-desorption experiments, which proved only a small reduction in adsorption properties. This study follows the current trend of waste utilization (fly ash) and the removal of pollutants from aqueous solutions with respect to their reuse, which remains in line with the goals of the circular economy.

Management of hazardous fly-ash energy waste in the adsorptive removal of diclofenac by the use of synthetic zeolitic materials

Zeolite-carbon composites (Na-P1(C), Na-X(C)) and pure zeolites (Na-P1, Na-X) were synthesized from hazardous high-carbon fly ash waste (HC FA) via hydrothermal reaction with sodium hydroxide (NaOH). These solids were applied in the removal of diclofenac (DCF) from aqueous solution, with and without poly(acrylic acid) (PAA). The experiments included adsorption-desorption measurements, as well as electrokinetic and stability analyses. The obtained results showed that HC FA and Na-P1(C) had the greatest adsorption capacity towards DCF, i.e., 26.51 and 21.19 mg/g, respectively. PAA caused considerable decrease in the DCF adsorption due to the competition of both adsorbates of anionic character for active sites. For example, the adsorbed amount of DCF on Na-P1 without PAA was 14.11 mg/g, whereas the one measured with PAA was 5.08 mg/g. Most of prepared solids were effectively regenerated by the use of NaOH. Desorption degree reached even 73.65% in the single systems (with one adsorbate) and 97.24% in the mixed ones (with two adsorbates). Zeolitic materials formed suspensions of rather low stability, which underwent further deterioration in the organic molecules presence. All the results obtained in this study indicated that HC FA can be successfully managed in the removal of organic substances.

Zeolite A powder and beads from sugarcane bagasse fly ash modified with iron(III) oxide-hydroxide for lead adsorption

The discharging of lead-contaminated wastewater is a concern because of its toxicity to living organisms and water quality resulting in dangerous water consumption, so it is highly recommended to remove lead from wastewater to be below water quality standards for a safe environment. Zeolite A sugarcane bagasse fly ash powder (ZB), zeolite A sugarcane bagasse fly ash powder mixed iron(III) oxide-hydroxide (ZBF), zeolite A sugarcane bagasse fly ash beads (ZBB), zeolite A sugarcane bagasse fly ash powder mixed iron(III) oxide-hydroxide beads (ZBFB), and zeolite A sugarcane bagasse fly ash beads coated iron(III) oxide-hydroxide (ZBBF) were synthesized and characterized in various techniques. Their lead removal efficiencies were investigated by batch experiments, adsorption isotherms, and kinetics. The specific surface area, pore volume, and pore size of ZB were close values to zeolite A standard (STD), and ZBF had the highest specific surface area and the smallest pore size than others. ZB and ZBF demonstrated crystalline phases whereas ZBB, ZBFB, and ZBBF were amorphous phases. The surface morphology of ZB was a cubic shape similar to STD. ZBF demonstrated an agglomerated formation of ZB and iron(III) oxide-hydroxide whereas ZBFB and ZBBF had sphere shapes with coarse surfaces. Si, Al, O, Fe, Na, Ca, O-H, (Si, Al)-O, H₂O, and D₄R were detected in all materials. The surface charges of all zeolite A materials had negatively charged at all pH values, and their surfaces increased more negatively charged with increasing pH value which pH 5 illustrated as the highest negatively charged in all materials. Their lead removal efficiencies were higher than 82%. Langmuir isotherm and pseudo-second-order kinetic models were well explained for their adsorption patterns and mechanisms. Finally, ZBBF is a good offer for applying in industrial wastewater treatment systems because of its easy operation and saving costs than ZBF.

Study on electrical double layer nanostructure on zeolitic materials’ surface in the presence of impurities of different nature

The aim of the research was to compare the adsorption mechanisms of heavy metal ions (Pb(II) and Zn(II)), as well as organic substances [diclofenac molecules and pol(acrylic acid) macromolecules on the surfaces of Na-X and Na-P1 synthetic zeolites as well their Na-X© and Na-P1© carbon composites]. The single and mixed adsorbate systems were considered. The more probable structures of the formed adsorption layers were proposed based on the results of the solid surface charge density and zeta potential experiments. The great applicability of the analysis of the parameters characterizing the electrical double layer in determination of the binding mechanism of simple inorganic ions and more complex organic molecules on the surface of the examined solids from the one- and two-component solutions was proved. Moreover, the changes of the surface and electrokinetic factors after the addition of the organic molecules enable specification of drug molecule orientation as well as the polymeric chain conformation at the solid/liquid interface.

Low-cost zeolitic carriers for delivery of hydroxychloroquine immunomodulatory agent with antiviral activity

The coronavirus pandemic prompted scientists to look for active pharmaceutical ingredients that could be effective in treating COVID-19. One of them was hydroxychloroquine, an antimalarial and immunomodulatory agent exhibiting antiviral activity. The anchoring of this drug on porous carriers enables control of its delivery to a specific place in the body, and thus increases bioavailability. In this work, we developed low-cost zeolitic platforms for hydroxychloroquine. The waste solution generated during zeolite production from fly ashes was used in the synthesis of Na-A and Na-X carriers at laboratory and technical scale. The materials were characterized by high purity and single mineral phase composition. The surface charge of zeolites varied from negative at pH 5.8, and 7.2, to positive at pH 1.2. All samples indicated good sorption ability towards hydroxychloroquine. The mechanism of drug adsorption was based on electrostatic interactions and followed the Freundlich model. Zeolitic carriers modified the hydroxychloroquine release profiles at conditions mimicking the pH of body fluids. The mode of drug liberation was affected by particle size distributions, morphological forms, and chemical compositions of zeolites. The most hydroxychloroquine controlled release at pH 5.8 for the Na-X material was noted, which indicates that it can enhance the drug therapeutic efficacy.

Activated Biocarbons Obtained from Plant Biomass as Adsorbents of Heavy Metal Ions

This paper deals with the adsorption of heavy metal ions on the surface of carbonaceous materials obtained via the chemical activation of biomass. Waste plum stones, pine sawdust and horsetail herb were used as the precursors of carbonaceous adsorbents. The effect of the precursor type and preparation procedure on the physicochemical properties of activated biocarbons and their sorption abilities towards Pb(II) and Cu(II) ions have been checked. The obtained micro-mesoporous activated biocarbons were characterized by determination of elemental composition and ash content, the number of surface functional groups and pH of water extracts as well as textural study based on low temperature nitrogen adsorption/desorption and scanning electron microscopy. Additionally, the electrokinetic studies including solid surface charge density and zeta potential determination were performed. Moreover, the adsorption data modelling (equilibrium and kinetics), XPS results analysis and comparison of parameters characterizing electrical double layer formed at the solid-liquid interface enabled the specification of the mechanism of heavy metals binding with the activated biocarbons surface. The maximum adsorption capacity towards copper and lead ions (177.5 and 178.1 mg/g, respectively) was found for plum stone-based activated biocarbon. For all carbonaceous materials, better fit to the experimental data was achieved with a Langmuir isotherm than a Freundlich one. In turn, a better fit of the kinetics data was obtained using the pseudo-second order model.

Removal of Chromium (VI) and Lead (II) from Aqueous Solution Using Domestic Rice Husk Ash- (RHA-) Based Zeolite Faujasite

Rice husk ash (RHA), is a widely available biobased source for high purity silica. In this work, zeolite Faujasite (FAU) is synthesized using extracted silica from RHA (collected from a local region of Bangladesh). The synthesized zeolite FAU was used as an adsorbent for Cr(VI) and Pb (II) batch-wise adsorptive removal from respective aqueous solution. The synthesized zeolite FAU was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen-sorption, and Fourier transfer infrared (FT-IR) spectroscopy. Metal ion adsorption studies were performed by varying metal concentration (20–100 mg/L for Cr(VI) and 900–133 mg/L for Pb(II)), sorbent dosage (2–10 g/L for chromium and 0.5–1.5 g/L for lead), and contact time (10–120 min for both metal ions). The maximum adsorption capacity of RHA-based zeolite FAU was found to be 3.56 mg/g and 342.16 mg/g for Cr(VI) and Pb(II), respectively. Since the sorption data was found to match with Langmuir isotherm, a monolayer adsorption was occurred. The regeneration of the RHA-based zeolite FAU by NaCl solution showed the potential of repeated as well as continuous operation.

Characterization of Cu(II) and Zn(II) Sorption onto Zeolite

In this study, a batch sorption study approach was combined with an instrumental analytical approach of atomic absorption spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) for the sorption of copper and zinc ions from aqueous solution on zeolites. Both copper and zinc are biogenic elements; nevertheless, many industrial processes produce an excessive amount, which is why their efficient removal from water must be studied. Two types of zeolites, Zeolite Micro 20 (Z-M20) and Zeolite Micro 50 (Z-M50), were used. The results showed that the maximum sorption capacities for removal of Cu and Zn were 1.06 for CuSO4, 42.35 for Cu(NO3)2, 1.15 for ZnSO4 and 2.29 for Zn(NO3)2 adsorption onto Z-M20 and 0.45 for CuSO4, 1.67 for Cu(NO3)2, 0.39 for ZnSO4 and 1.51 for Zn(NO3)2 adsorption onto Z-M50. The maximum sorption capacities are higher for sulfates and the sorbent with smaller particle size. The sorption capacities of Cu and Zn for corresponding anion and particle size differ only up to 5–15%. Using XRD and XPS analyses before and after the sorption process, it was found that the content of both Cu and Zn in the surface layer and the bulk are the same for sorption onto sorbent with smaller particle size, but are higher in the surface layer than in the bulk for sorption onto sorbent with larger particle size. One of the main findings of this study is that a zeolite with smaller particles takes Cu and Zn by the whole particle, while with bigger particles, Cu and Zn concentrate in the surface of the particle. The results of the study may be used as an indicator for sorption efficiency of the studied zeolites for their application in the treatment of copper and zinc contaminated effluents.

Dynamic Adsorption Properties of Insoluble Humic Acid/Tourmaline Composite Particles for Iron and Manganese in Mine Wastewater

Iron- and manganese-contaminated mine water is widespread around the world, and economical and efficient remediation has become a priority. Insoluble humic acid/tourmaline composite particles (IHA/TM) were prepared by combining inorganic tourmaline (TM) with the natural organic polymer humic acid (HA), and the effects of different calcination temperatures and calcination times of TM and IHA on the adsorption of Fe²⁺ and Mn²⁺ were analyzed. Based on the microscopic characterization of Scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS), Brunnauer–Emmet–Teller (BET), X-ray diffractometer (XRD) and Fourier transform infrared (FTIR), the simultaneous adsorption performance of IHA/TM on Fe²⁺ and Mn²⁺ was studied through dynamic adsorption tests, and a dynamic adsorption model was established. Adsorption regeneration experiments were carried out to further investigate the effectiveness of the composite particles in practical applications. The results show that, when the calcination temperature was 330 °C and the calcination time was 90 min, the removal rates of iron and manganese by the IHA/TM composite particles reached 99.85% and 99.51%, respectively. The curves for penetration of Fe²⁺ and Mn²⁺ ions into the IHA/TM composite particles were affected by the bed height, flow rate and influent concentration. Decreasing the flow rate, decreasing the influent concentration, or increasing the bed height prolonged the operation time of the dynamic column. If the bed height was too low, the penetration point was reached before the expected treatment was achieved, and when the bed height was too high, the removal of Fe²⁺ and Mn²⁺ was slow, and the utilization rate of the adsorbent was also reduced. If the flow rate was too low, longitudinal remixing easily occurred in the column. However, when the flow rate was too high, the speed of Fe²⁺ and Mn²⁺ ions passing through the adsorption layer increased, which reduced the total amount of adsorption. The increase in influent concentration not only reduces the removal rate, but also greatly shortens the total operation time of the dynamic column and reduces the treatment water. The dynamic process for the adsorption of Fe²⁺ and Mn²⁺ by IHA/TM was fitted best by the Thomas model. The adsorption column was continuously regenerated five times, and the results show that the IHA/TM composite particles were suitable for iron and manganese removal from mine wastewater. The research results will provide a reference for the effectiveness of the IHA/TM composite particles in practical applications.

A Review on the Effects of Organic Structure-Directing Agents on the Hydrothermal Synthesis and Physicochemical Properties of Zeolites

The study on the synthesis of zeolites, including both the development of novel techniques of synthesis and the discovery of new zeolitic frameworks, has a background of several decades. In this context, the application of organic structure-directing agents (SDAs) is one of the key factors having an important role in the formation of porous zeolitic networks as well as the crystallization process of zeolites. There are various elements that are needed to be explored for elucidating the effects of organic SDAs on the final physicochemical properties of zeolites. Although SDAs were firstly used as pore generators in the synthesis of high-silica zeolites, further studies proved their multiple roles during the synthesis of zeolites, such as their influences on the crystallization evolution of zeolite, the size of the crystal and the chemical composition, which is beyond their porogen properties. The aim of this mini review is to present and briefly summarize these features as well as the advances in the synthesis of new SDAs during the last decades.

Functionalization of Zeolite NaP1 for Simultaneous Acid Red 18 and Cu(II) Removal

The efficiency of azo dye Acid Red 18 (AR18) and Cu(II) ions simultaneous removal from an aqueous solution on NaP1CS and NaP1H was investigated, taking into account the effect of the phase contact time, pH, initial concentration, temperature, and interfering ions presence. Zeolite denoted as NaP1CS was modified by chitosan (CS) and zeolite denoted as NaP1H was modified by hexadecyltrimethylammonium bromide (HDTMA). In order to characterize sorption properties of NaP1CS, the obtained sorbent was characterized using Fourier transform infrared spectroscopy (FTIR) and nitrogen adsorption/desorption (ASAP). The kinetic parameters were determined by means of the pseudo first order (PFO), pseudo second order (PSO), and intraparticle diffusion (IPD) kinetic models. To present the adsorption data, three different isotherm models (Langmuir, Freundlich and Dubinin-Radushkevich) were used. The desorption process was also examined. It was found that for sorbent NaP1CS the pseudo second order (PSO) kinetic model and the Langmuir isotherm fitted best the experimental data. Moreover, it was noted that the acidic pH is appropriate to achieve the best sorption properties of NaP1CS for Cu(II) and NaP1H for AR18 and Cu(II). The thermodynamic parameters indicate an endothermic process. The most effective solution for the desorption process was found to be 1 M HCl. The results indicate that simultaneous removal of dye AR18 and Cu(II) on modified zeolite NaP1CS or NaP1H is possible and proceeds with a very good efficiency. The obtained zeolites could effectively adsorb AR18 an Cu(II) simultaneously, but their adsorption abilities were rather different.

Mixed-Phase Ion-Exchangers from Waste Amber Container Glass

This study investigated the one-pot hydrothermal synthesis of mixed-phase ion-exchangers from waste amber container glass and three different aluminium sources (Si/Al = 2) in 4.5 M NaOH_(aq) at 100 °C. Reaction products were characterised by X-ray diffraction analysis, Fourier transform infrared spectroscopy, ²⁷Al and ²⁹Si magic angle spinning nuclear magnetic resonance spectroscopy and scanning electron microscopy at 24, 48 and 150 h. Nitrated forms of cancrinite and sodalite were the predominant products obtained with reagent grade aluminium nitrate (Al(NO₃)₃∙9H₂O). Waste aluminium foil gave rise to sodalite, tobermorite and zeolite Na-P1 as major phases; and the principal products arising from amorphous aluminium hydroxide waste were sodalite, tobermorite and zeolite A. Minor proportions of the hydrogarnet, katoite, and calcite were also present in each sample. In each case, crystallisation was incomplete and products of 52, 65 and 49% crystallinity were obtained at 150 h for the samples prepared with aluminium nitrate (AN-150), aluminium foil (AF-150) and amorphous aluminium hydroxide waste (AH-150), respectively. Batch Pb²⁺-uptake (~100 mg g^-1) was similar for all 150-h samples irrespective of the nature of the aluminium reagent and composition of the product. Batch Cd²⁺-uptakes of AF-150 (54 mg g^-1) and AH-150 (48 mg g^-1) were greater than that of AN-150 (36 mg g^-1) indicating that the sodalite- and tobermorite-rich products exhibited a superior affinity for Cd²⁺ ions. The observed Pb²⁺- and Cd²⁺-uptake capacities of the mixed-product ion-exchangers compared favourably with those of other inorganic waste-derived sorbents reported in the literature.