Search Results (24)

This study explores the fabrication, structural characteristics, and performance of an innovative porous geopolymer membrane made from waste natural zeolite powder for Pb(II) removal, with potential applications in wastewater treatment. A hybrid geopolymer membrane incorporating polyvinyl acetate (PVAc) (10, 20, and 30 wt.%) was synthesized and thermally treated at 300 °C to achieve a controlled porous architecture. Characterization techniques, including Fourier-transform infrared spectroscopy (FTIR), revealed the disappearance of characteristic C=O and C-H stretching bands (~1730 cm⁻¹ and ~2900 cm⁻¹, respectively), confirming the full degradation of PVAc. Thermogravimetric analysis (TG) and differential scanning calorimetry (DSC) indicated a total mass loss of approximately 14.5% for the sample with PVAc 20 wt.%, corresponding to PVAc decomposition and water loss. Energy-dispersive spectroscopy (EDS) elemental mapping showed the absence of carbon residues post-annealing, further validating complete PVAc removal. X-ray diffraction (XRD) provided insight into the crystalline phases of the raw zeolite and geopolymer structure. Once PVAc removal was confirmed, the second phase of characterization assessed the membrane’s mechanical properties and filtration performance. The thermally treated membrane, with a thickness of 2.27 mm, exhibited enhanced mechanical properties, measured with a nano-indenter, showing a hardness of 1.8 GPa and an elastic modulus of 46.7 GPa, indicating improved structural integrity. Scanning electron microscopy (SEM) revealed a well-defined porous network. Filtration performance was evaluated using a laboratory-scale dead-end setup for Pb(II) removal. The optimal PVAc concentration was determined to be 20 wt.%, resulting in a permeation rate of 78.5 L/(m²·h) and an 87% rejection rate at an initial Pb(II) concentration of 50 ppm. With increasing Pb(II) concentrations, the flux rates declined across all membranes, while maximum rejection was achieved at 200 ppm. FTIR and EDS analyses confirmed Pb(II) adsorption onto the zeolite-based geopolymer matrix, with elemental mapping showing a uniform Pb(II) distribution across the membrane surface. The next step is to evaluate the membrane’s performance in a multi-cation water treatment environment, assessing the sorption kinetics and its selectivity and efficiency in removing various heavy metal contaminants from complex wastewater systems. Full article

Rapid population and economic growth have increased the demand for depleting resources. Nitrogen (N) and phosphorus (P) are mineral elements that perform important functions in plants, but their extraction is not sustainable. In addition, these elements contribute significantly to the eutrophication of water bodies. The recovery of these nutrients from wastewater by adsorption techniques offers a promising solution. Previous studies have demonstrated the adsorption capabilities of materials such as zeolite for ammonium (NH₄⁺) and biochar for P. In addition, these materials can serve as a source of N and P for plants in a circular economy context. In this regard, this study aims to evaluate the recovery of N and P by the adsorption capacities of zeolite and biochar through a column test with treated wastewater. Two columns positioned in series, one filled with 2.7 kg of zeolite and the other with 397 g of biochar, were placed at the outlet of the full-scale sewage treatment plant of Marineo (Italy). The zeolite adsorbed 3.6 g of NH₄⁺ accumulated during the test with a rate of adsorption of 44% and adsorption of 1.33 mg g⁻¹ of NH₄⁺. The biochar adsorbed about 11 g of P accumulated during the test, with an adsorption percentage of 13% and an adsorption of 26.75 mg g⁻¹ of P. Despite some problems related to the effluent used during the test, the tested materials showed good adsorption properties. Full article

Ion-adsorbing rare earth tailings (IRETs) contain a large amount of clay minerals, which are a potential source of silicon and aluminum for the preparation of zeolite materials. The complexity of the tailings’ composition and the impurity composition are the main difficulties in the controllable preparation of zeolite. Herein, IRETs were treated by classification activation technology for the preparation of IRET-ZEO, which was used for the removal of heavy metal Pb²⁺ in water. A new method of resource utilization of ion-type rare earth tailings is realized by “treating waste with waste”. The results showed that the IRETs were classified and then thermally activated, and the optimal activation parameter was calcination at 850 °C for 1 h. The optimal NaOH concentration used in the crystallization process was 5 mol/L, with a crystallization time of 3 h and a crystallization temperature of 85 °C, and the crystallization product was zeolite A. The removal rate of the Pb²⁺ solution with an initial concentration of 100 mg/L was as high as 96.7% in an acidic solution with a pH value from 2 to 5.5. In particular, when the solution pH was higher than 4.2, the adsorption rate of Pb²⁺ was close to 100%. The IRET-ZEO showed a fast adsorption rate (5 min to reach adsorption equilibrium), a large adsorption capacity (378.35 mg/g), excellent acid resistance, and selectivity and regenerability for Pb²⁺. This work provides a new strategy for the green resource utilization of IRETs and the treatment of lead-containing wastewater. Full article

In the framework of a circular economy, wastewater treatment should be oriented toward processes that allow the recovery of the resources present in the wastewater while ensuring good effluent quality. Nitrogen recovery is usually carried out in streams concentrated in this nutrient because these high concentrations facilitate nitrogen valorization. On the other hand, the mainstream of a wastewater treatment plant (WWTP) has a high potential for nitrogen recovery, but it is not usually considered because it is hard to manage due to its low nitrogen concentration. To solve this problem and facilitate the recovery of nitrogen in the mainstream, this work proposes ion exchange with zeolites as a stage of ammonium concentration, to provide a nitrogen-concentrated stream that could be valorized by another technology, while obtaining a nitrogen-free effluent. The working stream, the permeate of an AnMBR process in the mainstream, has suitable characteristics to be treated in an ion exchange column (free of suspended solids and with very low organic matter content). To this end, the effect of the working flow rate (17.5 to 4.4 BV/h) and the ammonium concentration (54 to 17 mg NH₄-N/L) on the adsorption capacity of the zeolite in the loading phase was evaluated. The adsorption curves were fitted to three mathematical models: Thomas, Bohart–Adams, and Yoon–Nelson. The effect of the regeneration flow rate (from 8.7 to 2.2 BV/h) and the regenerant concentration (NaOH at 0.2, 0.1, and 0.05 M) on regeneration capacity and efficiency were also studied. A novel control strategy based on effluent conductivity was used in both phases to control the duration of the adsorption and regeneration phases. Full article

Resource recovery from wastewater is very important in view of a circular economy approach in the water field. Among the different technologies applied to realize circular economy, an attractive option is the use of nutrient-enriched media that can be utilized as slow-release fertilizers. Zeolites have been re-discovered for their key role in ammonium (NH₄⁺) adsorption from treated wastewater. Although many studies have been carried out to assess the ability of zeolites to adsorb NH₄⁺, only few papers concerning NH₄⁺ desorption from zeolites are available in the literature. Therefore, this study investigated NH₄⁺ desorption from mineralogically different zeolites, before (ZNS and ZNC) and after (ZSS and ZSC) their treatment with sodium chloride. The zeolites differed in mordenite content. The amount of the desorbed NH₄⁺ varied from 78 to 84% of the total NH₄⁺ adsorbed. In particular, the NaCl-treated materials showed the largest desorption (27.6 ± 0.2 mg L⁻¹, and 27.9 ± 0.7 mg L⁻¹, ZSS, and ZSC, respectively) as compared to the untreated zeolites (22.9 ± 0.3 mg L⁻¹, and 24.2 ± 0.3 mg L⁻¹, ZNS, and ZNC, respectively) because of the different affinity of the cations for the zeolite surface. A monomodal pseudo-first-order model best approximated the desorption kinetics, suggesting only one mechanism of NH₄⁺ desorption from zeolites. Such a mechanism is based on the ion exchange between dissolved Na⁺ and adsorbed NH₄⁺. The desorption kinetics also showed that NH₄⁺ desorbed slower from the NaCl-treated zeolites than the untreated ones. This effect was explained by the different affinity of Na⁺ and NH₄⁺ for the zeolite surfaces as due to the diverse sizes of the Na⁺ and NH₄⁺ hydration spheres. By revealing the effect of zeolite mineralogy and surface treatments in the desorption of NH₄⁺, this study can suggest new and effective synthetic strategies for the achievement of cheap new materials to be applied in environmental remediation within a circular economy perspective. Full article

Zeolites are widely used in diverse applications, including the removal of heavy metals from wastewater. However, separating fine-sized zeolite particles from treated water is often a challenge. In this work, a novel method utilizing a colloidal polyvinyl alcohol (PVA) solution to bind iron oxide nanoparticles to a Linde Type A (LTA) zeolite was used to synthesize magnetic zeolite. Different zeolite–iron oxide nanoparticle loadings (10:1, 10:0.5, and 10:0.1) were used in batch adsorption experiments to investigate adsorption capacities and kinetics for Cu removal from an aqueous solution. The results showed that the magnetic zeolite maintained much of its adsorbent properties while facilitating a simplified process design. Thus, the adsorption capacity of pure LTA zeolite was found to be 262 mg/g for magnetic zeolite, with a 10:1 ratio—151 mg/g; 10:0.5—154 mg/g; and 10:0.1—170 mg/g. Magnetic separation was subsequently employed to remove the magnetic zeolite from the treated solution. Full article

This study is aimed to determine the performances of zeolite-water hyacinth ash (WHA)-clay (ZWC) pellets on removing nutrients (nitrogen (N) and phosphorus (P)) and heavy metal (HM). In this study, the adsorption experiments were conducted for various pellet compositions and sizes, the application of pre-treatment on pellets, and tested with different concentrations of synthetic wastewater. The results identified that the maximum removal capacities of ZWC pellet were 0.112 mg/g, 0.08 mg/g, 0.171 mg/g, and 0.151 mg/g for phosphate (PO₄), total phosphorus (TP), nitrate-nitrogen (NO₃), and total nitrogen (TN), respectively. The optimization experiment indicated that smaller pellet sizes and those treated with calcium hydroxide solution exhibited better N&P and HM removal performances. The optimized ZWC pellet was able to remove up to 90%, 86%, 94%, 90%, 84%, 86%, and 91% for PO₄, TP, NO₃, TN, zinc (Zn), copper (Cu), and lead (Pb), respectively, after 3 h of contact time. The ZWC pellet proved that it can be used as an effective adsorbent for wastewater treatment. Full article

The conventional wastewater treatment methods only remove up to 80% of total nitrogen (N) or phosphorus (P) from wastewater, so additional facilities are needed. This article describes a newly created other wastewater treatment unit (NCU) that increases the effectiveness of P and N removal of the small-scale biological wastewater treatment plant. This work aims to evaluate the capacity of simultaneous elimination from wastewater nitrogen (NH₄-N, NO₃-N) and phosphorus (PO₄-P) by adsorption. NCU was filled with the sorbent material zeolite (clinoptilolite) and OCS (Fe, Mn, Ca oxides coated sand). After treatment in the main plant, wastewater flows through the NCU without using electric power. A compact system consisting of a main treatment plant and the NCU worked for 4 months, as the harmonized European Standard EN 12566-7 recommended. The NCU unit reduced PO₄-P, NH₄-N, and NO₃-N concentrations in the effluent (74–98%, 52–99%, and 50–98%, respectively). In general, the small-scale system treated wastewater did not contain more than 1 mg/L phosphorus concentration and not more than 10 mg/L nitrogen concentration. This study demonstrates that treatment in NCU is an ecological and environmentally friendly method suitable for decentralized wastewater treatment. Full article

Natural zeolite is a widely used material with excellent environmental cleaning performance, especially in water and wastewater treatment. Natural zeolite (Z_ini) calcined by CO₂-laser radiation (ZL) was tested as a catalyst for the photodegradation and the adsorption of industrial azo dye Lanasol Yellow 4G (LY4G) in water. Morphology, chemical structure, and surface composition of Z_ini and ZL were analyzed by XRD, SEM, EDS, and XPS. UV/Visible spectrophotometry was used to evaluate the photocatalytic activity of Z_ini and ZL. The photocatalytic activity of the studied zeolites was associated with the presence of Fe oxides in their composition. Laser-treated natural zeolite showed higher efficiency as a photocatalyst compared to untreated natural zeolite. Full article

This work investigates the applicability of clinoptilolite, a natural zeolite, as a low-cost adsorbent for removing chromium from aqueous solutions using fixed bed studies. To improve its removal performance for the inorganic pollutant, the adsorbent is pretreated with NaCl to prepare it in the homoionic form of Na⁺ before undertaking ion exchange with Cr³⁺ in aqueous solution. This work also evaluates if treated effluents could meet the required effluent discharge standard set by legislation for the target pollutant. To sustain its cost-effectiveness for wastewater treatment, the spent adsorbent is regenerated with NaOH. It was found that the clinoptilolite treated with NaCl has a two-times higher Cr adsorption capacity (4.5 mg/g) than the as-received clinoptilolite (2.2 mg/g). Pretreatment of the clinoptilolite with NaCl enabled it to treat more bed volume (BV) (64 BV) at a breakthrough point of 0.5 mg/L of Cr concentration and achieve a longer breakthrough time (1500 min) for the first run, as compared to as-received clinoptilolite (32 BV; 250 min). This suggests that pretreatment of clinoptilolite with NaCl rendered it in the homoionic form of Na⁺. Although pretreated clinoptilolite could treat the Cr wastewater at an initial concentration of 10 mg/L, its treated effluents were still unable to meet the required Cr limit of less than 0.05 mg/L set by the US Environmental Protection Agency (EPA). Full article

1,4-Dioxane is a contaminant of emerging concern and a probable human carcinogen that has been widely detected in aqueous environments. However, the removal of 1,4-dioxane by conventional water and wastewater treatment plants had proven to be ineffective due to its unique physicochemical properties. The development of innovative technologies for both in-situ and ex-situ treatment of 1,4-dioxane to meet increasingly strict standards is in urgent need. This review summarizes the current available physicochemical and biological treatment technologies for the removal of 1,4-dioxane from both water and wastewater and the strategies that may potentially fulfill the stringent 1,4-dioxane standard were discussed. Advanced oxidation processes (AOPs), such as ultraviolet radiation coupled with H₂O₂ (8–10 mg L⁻¹), had shown efficient 1,4-dioxane destruction and had already been applied for both water and wastewater treatment processes. On the other hand, more than 30 pure microbial strains and microbial communities that can metabolically or metabolically degrade 1,4-dioxane were reported. Biodegradation has been proven to be a feasible and cost-effective approach for 1,4-dioxane remediation. Suspended growth bioreactor, immobilized cell bioreactor, and biofiltration systems were the most commonly used biological approaches to remove 1,4-dioxane from contaminated water. Though 1,4-dioxane easily desorbs after the adsorption by materials such as granular activated carbon (GAC) and zeolite, temporary 1,4-dioxane removal by adsorption followed by 1,4-dioxane biodegradation in the bioaugmented adsorption media may be a feasible strategy treating 1,4-dioxane contaminated water. Overall, the treatment chain that combines physical-chemical processes and biodegradation has a great potential for synergistic removal of 1,4-dioxane at lower operating costs. Full article

The increase of global environmental restrictions concerning solid and liquid industrial waste, in addition to the problem of climate change, which leads to a shortage of clean water resources, has raised interest in developing alternative and eco-friendly technologies for recycling and reducing the amount of these wastes. This study aims to utilize Sulfuric acid solid residue (SASR), which is produced as a useless waste in the multi-processing of Egyptian boiler ash. A modified mixture of SASR and kaolin was used as the basic component for synthesizing cost-effective zeolite using the alkaline fusion-hydrothermal method for the removal of heavy metal ions from industrial wastewater. The factors affecting the synthesis of zeolite, including the fusion temperature and SASR: kaolin mixing ratios, were investigated. The synthesized zeolite was characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), particle size analysis (PSD) and N₂ adsorption-desorption. The SASR: kaolin weight ratio of 1:1.5 yields faujasite and sodalite zeolite with 85.21% crystallinity, which then shows the best composition and characteristics of the synthesized zeolite. The factors affecting the adsorption of Zn²⁺, Pb²⁺, Cu²⁺, and Cd²⁺ ions from wastewater on synthesized zeolite surfaces, including the effect of pH, adsorbent dosage, contact time, initial concentration, and temperature, have been investigated. The obtained results indicate that a pseudo-second-order kinetic model and Langmuir isotherm model describe the adsorption process. The maximum adsorption capacities of Zn²⁺, Pb²⁺, Cu²⁺, and Cd²⁺ ions onto zeolite at 20 °C were 12.025, 15.96, 12.247, and 16.17 mg·g⁻¹, respectively. The main mechanisms controlling the removal of these metal ions from aqueous solution by synthesized zeolite were proposed to be either surface adsorption, precipitation, or ion exchange. The quality of the wastewater sample obtained from the Egyptian General Petroleum Corporation (Eastern Desert, Egypt) was highly improved using the synthesized zeolite and the content of heavy metal ions was significantly reduced, which enhances the utilization of the treated water in agriculture. Full article

Anaerobic Membrane Bioreactor technology has great advantages for treating wastewater, including energy recovery from organic matter. However, when the legislation requires that effluent standards be met in sensitive areas, this treatment cannot remove the nutrients, thus the permeate generated needs post-treatment. Apart from the biological processes, ion exchange is an alternative treatment for this stream since it can remove nutrients and concentrate them for later recovery as fertilizers. In this work, the feasibility of using a natural zeolite (clinoptilolite) for treating NH₄ from AnMBR permeate was studied and tests were carried out on the adsorption kinetics of ammonium. Isotherm tests verified that activating natural zeolite to its -Na form improves its performance by 20% and increases q_e from 2.37 to 2.86 mg NH₄-N/g for a Co of 30 mg NH₄-N/L. It was also found that the cations present in the water (especially Ca²⁺ and Na⁺) caused a 22% reduction in ammonium adsorption while organic matter was responsible for improving the retained ammonium by 22%. It was also found that the working pH (7.2 ± 0.2) is close to the optimal pH range (6–7) for zeolite performance. The tests on the AnMBR permeate indicate that clinoptilolite is a suitable material since treating this stream can retain up to 7.44 mg NH₄-N/g. Full article

The recovery and immobilization of metals from wastewater often occurs in an acidic environment that destroys the structure of adsorbents such as zeolites, which are porous crystalline aluminosilicates. The influence of hydrochloric acid solutions on the structure and properties of two natural mixtures of heulandite (HEU) and chabazite (CHA)—tuff from the Georgian Dzegvi-Tedzami deposit (HEU/CHA ≈ 8) and rock from the Kazakhstani deposit Chankanay (HEU/CHA≈1)—was studied by the X-ray energy dispersion spectra and diffraction patterns, as well as by adsorption of water, benzene, and nitrogen methods. It was found that acid-mediated dealumination, decationization, dissolution, and changes in systems of micro- and mesopores depend on the nature and chemical composition of the initial zeolites. It is concluded that, under the influence of acid, (i) zeolite micropores become accessible to relatively large molecules and ions, and the surface area of the adsorbent increases; (ii) the volume of mesopores decreases, and pores with a diameter of less than 4 nm become predominant; (iii) in terms of the degree of dealumination and dissolution rate, Kazakhstani zeolite is more acid-resistant than Georgian heulandite; and (iv) Kazakhstani zeolite retains a high ion-exchange capacity in an acidic environment, while Georgian heulandite, treated with dilute hydrochloric acid solutions, uptakes relatively high amounts of valuable silver, copper, and zinc. Full article

The development of an efficient adsorbent is required in tertiary wastewater treatment stages to reduce the phosphate–phosphorous content within regulatory levels (1 mg L⁻¹ total phosphorous). In this study, a natural muscovite was used for the preparation of muscovite/zeolite composites and the incorporation of Fe³⁺/Mn²⁺ (oxy)hydroxide nanoparticles for the recovery of phosphate from synthetic wastewater. The raw muscovite MC and the obtained muscovite/sodalite composite LMC were used in the powder form for the phosphate adsorption in batch mode. A muscovite/analcime composite was obtained in the pellets PLMCT₃ and monolith SLMCT₂ forms for the evaluation in fixed-bed mode for continuous operation. The effect of pH, equilibrium and kinetic parameters on phosphate adsorption and its further reuse in sorption–desorption cycles were determined. The characterization of the adsorbents determined the Fe³⁺ and Mn²⁺ incorporation into the muscovite/zeolite composite’s structure followed the occupancy of the extra-framework octahedral and in the framework tetrahedral sites, precipitation and inner sphere complexation. The adsorbents used in this study (MC, LMC, PLMCT₃ and SLMCT₂) were effective for the phosphate recovery without pH adjustment requirements for real treated wastewater. Physical (e.g., electrostatic attraction) and chemical (complexation reactions) adsorption occurred between the protonated Fe³⁺/Mn²⁺ (oxy)hydroxy groups and phosphate anions. Higher ratios of adsorption capacities were obtained by powder materials (MC and LMC) than the pellets and monoliths forms (PLMCT₃ and SLMCT₂). The equilibrium adsorption of phosphate was reached within 30 min for powder forms (MC and LMC) and 150 min for pellets and monoliths forms (PLMCT₃ and SLMCT₂); because the phosphate adsorption was governed by the diffusion through the internal pores. The adsorbents used in this study can be applied for phosphate recovery from wastewater treatment plants in batch or fixed-bed mode with limited reusability. However, they have the edge of environmentally friendly final disposal being promissory materials for soil amendment applications. Full article