Coal fly ash derived zeolite for highly efficient removal of Ni2+ inwaste water

Adsorption of metal porphyrins using chitosan/zeolite-X composite as an efficient demetallization agent for crude oil: Isotherm, kinetic, and thermodynamic studies

Chitosan/zeolite-X (CHS/ZX) was synthesized to serve as an effective adsorbent for metal porphyrins through adsorption processes as an alternative to traditional separation methods from crude oil. The adsorption-desorption mechanisms of vanadyl and nickel tetraphenyl porphyrin (VO-TPP and Ni-TPP) were conducted on the model solution. Compared to individual components CHS and ZX, the CHS/ZX composite exhibited a doubled capacity for metal porphyrin removal. The synthesized composite was systematically characterized using FESEM, BET, XRD, FTIR, TGA, XPS, and CHN analyses. The study investigated the impact of many factors, including temperature, initial metal-porphyrin concentration, CHS/ZX dose, and contact time, on the adsorption efficiency of metal-porphyrin using CHS/ZX adsorbents. The adsorption processes of VO-TPP and Ni-TPP on CHS/ZX were effectively assessed through various equilibrium models, such as Langmuir, Freundlich, and Dubinin-Radushkevich (D-R). The pseudo-second-order model accurately depicted the adsorption processes of both VO-TPP and Ni-TPP. Determining the point of zero charge (pHPZC) highlighted the composite's surface charge distribution. Furthermore, considering the ΔG° and ΔH° values, the adsorption processes at different temperatures are exothermic, and VO-TPP exhibits a greater adsorption capacity than Ni-TPP under similar conditions. Notably, 73.7 % of VO-TPP and 83.8 % of Ni-TPP that were adsorbed were successfully recovered.

Synthesis of zeolite from industrial wastes: a review on characterization and heavy metal and dye removal

Increasing world population, urbanization, and industrialization have led to an increase in demand in production and consumption, resulting in an increase in industrial solid wastes and pollutant levels in water. These two main consequences have become global problems. The high Si and Al content of solid wastes suggests that they can be used as raw materials for the synthesis of zeolites. In this context, when the literature studies conducted to obtain synthetic zeolites are evaluated, it is seen that hydrothermal synthesis method is generally used. In order to improve the performance of the hydrothermal synthesis method in terms of energy cost, synthesis time, and even product quality, additional methods such as alkaline fusion, ultrasonic effect, and microwave support have been developed. The zeolites synthesized by different techniques exhibit superior properties such as high surface area and well-defined pore sizes, thermal stability, high cation exchange capacity, high regeneration ability, and catalytic activity. Due to these specific properties, zeolites are recognized as one of the most effective methods for the removal of pollutants. The toxic properties of heavy metals and dyes in water and their carcinogenic effects in long-term exposure pose a serious risk to living organisms. Therefore, they should be treated at specified levels before discharge to the environment. In this review study, processes including different methods developed for the production of zeolites from industrial solid wastes were evaluated. Studies using synthetic zeolites for the removal of high levels of health and environmental risks such as heavy metals and dyes are reviewed. In addition, EPMA, SEM, EDX, FTIR, BET, AFM, and 29Si and 27Al NMR techniques, which are characterization methods of synthetic zeolites, are presented and the cation exchange capacity, thermodynamics of adsorption, effect of temperature, and pH are investigated. It is expected that energy consumption can be reduced by large-scale applications of alternative techniques developed for zeolite synthesis and their introduction into the industry. It is envisaged that zeolites synthesized by utilizing wastes will be effective in obtaining a green technology. The use of synthesized zeolites in a wide variety of applications, especially in environmental problems, holds great promise.

The efficient uptake of uranium by amine-functionalized β-cyclodextrin supported fly ash composite from polluted water

A novel polyethyleneimine/polydopamine-functionalized β-cyclodextrin supported fly ash adsorbent (PEI/PDA/β-CD/FA) had been synthesized to uptake uranium from polluted water. At pH = 5.0 and T = 298 K, the uranium uptake efficiency and capacity of PEI/PDA/β-CD/FA reached to 98.7 % and 622.8 mg/g, respectively, which were much higher than those of FA (71.4 % and 206.7 mg/g).The excellent uranium uptake properties of PEI/PDA/β-CD/FA could be explained by three points: (1) using β-CD as a supporting material could effectively avoid the aggregation of FA and improve the hydrophily of FA; (2) the unique cavity structure of β-CD could form chelates with uranyl ions; (3) the formation of PEI/PDA co-deposition coating on FA further enhanced the affinity of FA to UO22+. With the presence of interfering ions, the uptake efficiency of PEI/PDA/β-CD/FA for uranium was still up to 94.5 % after five cycles, indicating the high selectively and recoverability of PEI/PDA/β-CD/FA. In terms of the results of characterizations, uranium was captured by PEI/PDA/β-CD/FA via electrostatic attraction, hydrogen bond, coordination and complexation. To sum up, PEI/PDA/β-CD/FA was expected to be used for actual sewage treatment owing to its excellent uranium uptake efficiency/capacity, selectivity, cycle stability and feasibility of actual application.

Adsorption properties and mechanism of Cu(II) on virgin and aged microplastics in the aquatic environment

Microplastics (MPs) migrate by adsorbing heavy metals in aquatic environments and act as their carriers. However, the aging mechanisms of MPs in the environment and the interactions between MPs and heavy metals in aquatic environments require further study. In this study, two kinds of materials, polyamide (PA) and polylactic acid (PLA) were used as target MPs, and the effects of UV irradiation on the physical and chemical properties of the MPs and the adsorption behavior of Cu(II) were investigated. The results showed that after UV irradiation, pits, folds and pores appeared on the surface of aged MPs, the specific surface area (SSA) increased, the content of oxygen-containing functional groups increased, and the crystallinity decreased. These changes enhanced the adsorption capacity of aged MPs for Cu(II) pollutants. The adsorption behavior of the PA and PLA MPs for Cu(II) conformed to the pseudo-second-order model and Langmuir isotherm model, indicating that the monolayer chemical adsorption was dominant. The maximum amounts of aged PA and PLA reached 1.415 and 1.398 mg/g, respectively, which were 1.59 and 1.76 times of virgin MPs, respectively. The effects of pH and salinity on the adsorption of Cu(II) by the MPs were significant. Moreover, factors such as pH, salinity and dosage had significant effects on the adsorption of Cu(II) by MPs. Oxidative complexation between the oxygen-containing groups of the MPs and Cu(II) is an important adsorption mechanism. These findings reveal that the UV irradiation aging of MPs can enhance the adsorption of Cu(II) and increase their role as pollutant carriers, which is crucial for assessing the ecological risk of MPs and heavy metals coexisting in aquatic environments.

Synthesis of a high-iron fly-ash-based Na-X molecular sieve and its application in the adsorption of low concentration of CO2

In addressing the environmental challenges posed by the accumulation of fly ash (FA), efforts have been geared towards its high-value utilization. By the use of high-iron FA as a raw material, a high-iron fly-ash-based Na-X molecular sieve was successfully synthesized by hydrothermal method. We combined pretreatment methods such as high-temperature calcination, acid leaching and alkali fusion activation. The as-synthesized product was used for the adsorption of a low concentration of CO2, and the adsorption data were fitted by a physical model. The changes in iron content in pretreatment and molecular sieve synthesis were revealed by SEM-mapping, UV-Raman and UV-Vis. The results showed that the pretreatment process reduces the iron content from 32.3% to 13.3%, and converts the inactive phases to active phases, with n (SiO2/Al2O3) = 4.94. The activated product was transformed further to a Na-X molecular sieve using a hydrothermal method. The product has a single crystal phase and octahedral crystal structure. Its specific surface area was 646.634 m2 g-1, and micropores were distributed between 0.46 nm and 0.71 nm, with a mesoporous phase of 4.6 nm. When used to adsorb a low concentration of CO2, the Na-X molecular sieve has a high adsorption capacity of 3.70 mmol g-1, which reaches 95.11% that of the commercial Na-X molecular sieve. The adsorption breakthrough time and adsorption capacity decreased with an increase in temperature. The adsorption kinetics were consistent with the Bangham model for surface pore adsorption and Weber-Morris model for internal diffusion. During the synthesis process, iron was converted from highly dispersed iron oxide to four-coordinated framework iron. Thus, this paper paves a path for the high-quality transformation and utilization of high-iron fly-ash.

Synthesised and modified zeolite for effective management of beryllium contaminants in aqueous media under different conditions

The effective management of beryllium (Be) in solution is not well established. In this study, zeolite was synthesised from coal fly ash (CFA) and further modified to enhance Be sorption. Results indicated zeolite NaP1 was effectively synthesised, and cross-linked chitosan was grafted in/on the zeolite structure during modification. The Brunauer, Emmett, and Teller (BET) surface area substantially increased from 1.05 m2/g in CFA to 94.0 m2/g in the synthesised zeolite (SZ). Furthermore, the modified zeolite (MZ) showed improved functionality as a reactive site for Be sorption. A comparative sorption study revealed inferior sorption (11.3 %) and higher desorption (56.1 %) of Be using CFA than the sorption using SZ (93.0 % sorption, 2.9 % desorption) and MZ (93.0 % sorption, 1.5 % desorption). Consequently, SZ and MZ exhibited higher sorption efficacy than commercial zeolite (57.4 %) and other commercial sorbents. At an experimental pH of 5.5 [relevant to the pH of Little Forest Legacy Waste Site (LFLS) soil, a representative site for potential Be contamination], MZ showed higher sorption than SZ. The higher sorption in MZ resulted from its elevated ligand complexation [with nitrogen (N), phosphorous (P), and oxygen (O)] and some ion exchange (with Na+, -NH3+, and H+ ions) mechanisms. Moreover, increased sorption (up to 99 %) was observed using colloidal soil solution (CSS) collected from LFLS soil to simulate field conditions after extensive rainfall. Different environmental factors (e.g. pH, temperature, time, CSS, concentrations of sorbate, and sorbent) regulated Be sorption. The sorption mechanism was best described by the Langmuir model, and the pseudo-second-order kinetic model (R2 = 0.999). Moreover, the sorption reaction was spontaneous (ΔG = -Ve), enthalpically, and entropically influenced. Desorption hysteresis (ndesorption/nsorption < 1) suggested irreversible sorption, and the chemisorption mechanism of Be was confirmed by Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) analysis.

Fusion-Assisted Hydrothermal Synthesis of Technogenic-Waste-Derived Zeolites and Nanocomposites: Synthesis, Characterization, and Mercury (II) Adsorption

This study presents the synthesis of zeolites derived from coal fly ash (CFA) using the fusion-assisted alkaline hydrothermal method. The zeolites were synthesized by combining CFA and NaOH at a molar ratio of 1:1.2 under fusion temperatures of 500, 600, and 700 °C. Subsequently, the obtained zeolites were subjected to further modifications through the incorporation of magnetic (Fe₃O₄) and silver (Ag⁰) nanoparticles (NPs). The Fe₃O₄ NPs were introduced through co-precipitation of Fe(NO₃)₂ and FeCl₃ at a molar ratio of 1:1, followed by thermal curing at 120 °C. On the other hand, the Ag⁰ NPs were incorporated via ion exchange of Na⁺ with Ag⁺ and subsequent reduction using NaBH₄. The synthesized porous materials exhibited the formation of zeolites, specifically analcime and sodalite, as confirmed by X-ray diffraction (XRD) analysis. Additionally, the presence of Fe₃O₄ and Ag⁰ NPs was also confirmed by XRD analysis. The elemental composition analysis of the synthesized nanocomposites further validated the successful formation of Fe₃O₄ and Ag⁰ NPs. Nitrogen porosimetric analysis revealed the formation of a microporous structure, with the BET surface area of the zeolites and nanocomposites ranging from 48.6 to 128.7 m²/g and pore sizes ranging from 0.6 to 4.8 nm. The porosimetric characteristics of the zeolites exhibited noticeable changes after the modification process, which can be attributed to the impregnation of Fe₃O₄ and Ag⁰ NPs. The findings of this research demonstrate the effectiveness of the fusion-assisted method in producing synthetic zeolites and nanocomposites derived from CFA. The resulting composites were evaluated for their potential application in the removal of mercury ions from aqueous solutions. Among the samples tested, the composite containing Ag⁰ NPs exhibited the highest adsorption capacity, reaching 107.4 mg of Hg²⁺ per gram of composite. The composites modified with Fe₃O₄ NPs and Ag/Fe₃O₄ nanocomposites displayed adsorption capacities of 68.4 mg/g and 71.4 mg/g, respectively.

Emerging waste-to-wealth applications of fly ash for environmental remediation: A review

The considerable increase in world energy consumption owing to rising global population, intercontinental transportation and industrialization has posed numerous environmental concerns. Particularly, in order to meet the required electricity supply, thermal power plants for electricity generation are widely used in many countries. However, an annually excessive quantity of waste fly ash up to 1 billion tones was globally discarded from the combustion of various carbon-containing feedstocks in thermoelectricity plants. About half of the industrially generated fly ash is dumped into landfills and hence causing soil and water contamination. Nonetheless, fly ash still contains many valuable components and possesses outstanding physicochemical properties. Utilizing waste fly ash for producing value-added products has gained significant interests. Therefore, in this work, we reviewed the current implementation of fly ash-derived materials, namely, zeolite and geopolymer as efficient adsorbents for the environmental treatment of flue gas and polluted water. Additionally, the usage of fly ash as a catalyst support for the photodegradation of organic pollutants and reforming processes for the corresponding wastewater remediation and H₂ energy generation is thoroughly covered. In comparison with conventional carbon-based adsorbents, fly ash-derived geopolymer and zeolite materials reportedly exhibited greater heavy metal ions removal and reached the maximum adsorption capacity of about 150 mg g^-1. As a support for biogas reforming process, fly ash could enhance the activity of Ni catalyst with 96% and 97% of CO₂ and CH₄ conversions, respectively.

Zeolite fly ash-enhanced coagulation treatment of oil recovery wastewater from polymer flooding

Herein, an enhanced coagulation model is proposed in which zeolite is used as a crystal nucleus to promote flocs. The zeolite is prepared from fly ash by microwave-assisted hydrothermal synthesis. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and specific surface area and pore size analysis (BET) characterization confirmed the successful synthesis of ZFA, and improved the surface properties. Thus, the adsorption capacity of ZFA as crystal nucleus was improved, which enabled it to achieve better results in the process of enhanced coagulation. Compared with those of conventional coagulation, the oil content and SS removal rate of ZFA-enhanced coagulation increased by 85% and 44%, respectively. Compared with that of CFA-enhanced coagulation, the oil removal efficiency increased by 4%, and the SS removal efficiency increased by 9%. The optimal conditions of ZFA-enhanced coagulation were as follows: ZFA dosage of 100 mg/L, pH value of 5-8, ZFA particle size range of 60-75 μm, temperature of 40-50 ℃, and precipitation time of 30 min.

Ammonium continuous removal by zeolite P synthesized using fly ash combined with bacteria in aqueous solution

The new composite product synthesized by zeolite P and bacteria consisting of nitrobacteria and denitrobacteria can efficiently and continuously remove ammonium in solution through zeolite adsorption and bacteria degradation. In this study, we used fly ash to prepared zeolite P, and then combined bacteria to synthesize the composite product. The adsorption efficiency and mechanism of products for ammonium were further studied by batch and dynamic experiments, and adsorption model. The zeolite P with a relative crystallinity of 84.7% was synthesized using fly ash by an alkali fusion-hydrothermal method. The synthetic zeolite P could combine with bacteria to be prepared an integral adsorption composite that had hierarchical pore structure including macropores, mesopores, and micropores, and its maximum compressive strength reached 106.2 N. The zeolite P could remove ammonium from solution, and Freundlich, Temkin, and Dubinin-Radushkevich models as well as thermodynamic models all showed that the ammonium adsorption by zeolite was mainly physical adsorption. Thus, the adsorbed ammonium was easy to be desorbed and became the nitrogen source for bacteria in composites. By batch experiments, the ammonium adsorption rate of composite product was significantly improved (P < 0.05) compared with zeolite P due to zeolite adsorption and the bacteria degradation. Through dynamic experiments, the composite product could efficiently and continuously remove ammonium from solution than zeolite P and bacteria alone. Therefore, the composite product could form a stable system for the adsorption, desorption, and degradation of ammonium in solution.

Surfactant modified waste ash for the removal of chloro and nitro group substituted benzene from wastewater

A surfactant-modified coal fly ash was developed as a multifunctional adsorbent for the removal of organic pollutants from wastewater. Sodium dodecyl sulfate (SDS) was used to modify the surface of coal fly ash (CFA). The modified CFA was characterized using scanning electron microscopy (SEM), surface porosity analyzer, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The results showed that loading CFA with SDS not only improved the functionality and surface morphology of the raw ash for the adsorption of organic pollutants, but also enhanced its thermal stability. The efficiency of the modified fly ash was tested in terms of removal of two non-polar organic pollutants namely chlorobenzene (CB) and nitrobenzene (NB) from aqueous phase. The maximum uptake capacity of chlorobenzene and nitrobenzene with SDS-modified coal fly ash (SCFA) was 225 mg/g and 90 mg/g, respectively. The kinetic analysis was done by controlled kinetic models, i.e., pseudo first and second order kinetic models. The results showed that adsorption of CB and NB onto SCFA followed a pseudo second order kinetic model. The adsorption of chlorobenzene was exothermic over the modified adsorbent while nitrobenzene showed an endothermic behavior. The isotherm analysis depicted the multilayer adsorption of both pollutants onto the surface of the surfactant modified adsorbent. This work has shown that surface modification using surfactants can be a viable option to enhance the adsorption capacity of fly ash for pollutants removal.

Performance and mechanisms of fly ash for graphene oxide removal from aqueous solution

The potential wide use of graphene oxide in various fields results in the possibility of its dispersion throughout natural water systems, with a negative impact on organisms and ecosystems. This study evaluated the removal of graphene oxide (GO) from water by fly ash (FA). The effects of various conditions (including the initial concentration of graphene oxide, the pH of the initial solution, the amount of absorbent, and temperature) on the removal rate of GO were investigated in detail. The results show that the maximum removal rate of graphene oxide by fly ash is 93%; the isotherm adsorption process conforms to a Langmuir model; the adsorption reaction is a spontaneous exothermic process. Under optimal conditions, the pH of the solution was adjusted to 6, the amount of fly ash was 5 mg, the initial concentration of GO was 60 mg·L^-1, and the temperature was 303 K. Using X-ray diffraction (XRD), Raman spectroscopy (Raman), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), transmission electron microscopy (TEM), Zeta potential and X-ray electron spectroscopy (XPS), the adsorption mechanism was characterized. The experimental results demonstrate that fly ash is a good material for GO removal from aqueous solution.

Synthesis of zeolites from residual diatomite using a microwave-assisted hydrothermal method

Population growth directly affects the industrial production sector, as well as the quantities of waste generated in this sector. Diatomite is a typical example of such industrial waste and is used for the filtration of various products. With the aim of increasing its value, the present study employs this residue, following its usage in beer filtration, as a silicon source for the synthesis of zeolites. Two synthetic routes are used, namely, hydrothermal treatment with and without a pre-treatment step in a conventional microwave for 3-24 h. The results of the compositional and morphological characterization show that the use of a few minutes of microwave radiation reduces the process of zeolite synthesis to 15 h compared to the synthesis without pre-treatment, as well as reducing the production costs. The efficiency of microwave radiation is assessed with regards to solubilizing the residue, the possibility of employing a device of conventional use and the possibility of putting to use the diatomite residue, turning it into a versatile material that can be applied in several areas and process, such as industrial catalysts, the adsorption of environmental pollutants (ions and molecules) and water treatment via ion-exchange resins.

Recycling of Waste Solution after Hydrothermal Conversion of Fly Ash on a Semi-Technical Scale for Zeolite Synthesis

Nowadays, using fly ash for zeolites production has become a well-known strategy aimed on sustainable development. During zeolite synthesis in a hydrothermal conversion large amount of post-reaction solution is generated. In this work, the solution was used as a substrate for Na-A and Na-X zeolites synthesis at laboratory and technical scale. Obtained materials were characterized using particle size analysis, X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FTIR), and nitrogen adsorption/desorption isotherm. Produced zeolites revealed high purity (>98%) and monomineral zeolitic phase composition. The SiO₂ content was in the range 39–42% and 40–38%, whereas Al₂O₃ content was 23–22% and 25–26% for Na-X and Na-A, respectively. TEM and BET analyses revealed Na-X zeolite pores were almost identical to commercial 13X with S_BET in the range 671–734 m²/g. FTIR indicated slight differences between materials obtained at laboratory and technical scale in Si-O-(Si/Al) bridges of the zeolitic skeleton. The results showed good replicability of the laboratory process in the larger scale. The proposed method allows for waste solution reusability with a view to highly pure zeolites production in line with circular economy assumptions.

A Novel Open-System Method for Synthesizing Muscovite from a Biotite-Rich Coal Tailing

According to the wide application of muscovite in various industries, many studies have focused on its fabrication. However, the process of its synthesis faces long-standing challenges mainly related to the elevated temperature and pressure ambient, together with time and cost-consuming processes. This research work aims at synthesizing muscovite through a straightforward and direct wet thermal oxidation of an ash sample produced from biotite-rich coal tailings. For this purpose, the lab ash powder was mixed with 35% H2O2 at the room temperature of 25 °C while stirring at 480 rpm. Then, the temperature was gradually raised to 80 °C, and the process ran for 180 min. The dried product and the raw lab ash were characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR) methods. The XRD results indicated that the biotite was efficiently converted to the muscovite as the number of relevant peaks was significantly increased in the synthesized product’s pattern. The SEM and FTIR results showed some structural changes, from pseudo-hexagonal in the starting material to amorphous pseudo-crystals in the synthetic product, as well as the growth of the product’s crystals. The crystallographic study and lattice parameter calculations revealed that the starting material and product peaks matched to International Center for Diffraction Data (ICDD reference patterns of 01-080-1110 and 01-082-2450 for the biotite and the muscovite, respectively. Moreover, the calculation of the mean crystallite size of the starting material and treated samples were obtained as 55 nm and 87 nm, respectively. Finally, according to the characterization properties of synthesized muscovite, the presented method was introduced as an effective technique. Therefore, we highly suggest it for further consideration and its development in future investigations.

Mg17Al12 phase in magnesium alloy waste facilitating the Ni2+ reduction in nickel plating wastewater

A process for recycling Ni²⁺ in Ni-plating wastewater was investigated. This study employed Mg alloy flash waste to reduce the Ni²⁺ in the wastewater into metallic Ni. Fine second-phase Mg₁₇Al₁₂ in a network is the critical point for promoting the reduction reaction of Ni²⁺. The microstructures of the Mg alloy flash scrap and the die-cast Mg alloy scrap waste fulfilled the requirement. The Mg₁₇Al₁₂ is like a catalyst for the quick reduction of the Ni²⁺ ions into pure Ni metal. Contrarily, pure Mg (not containing Mg₁₇Al₁₂ particles) and gravity-cast AZ91D Mg alloy (having coarse Mg₁₇Al₁₂ particles) were not suitable for being used for the Ni²⁺ wastewater treatment. Based on the above results and discussion, using the Mg alloy flash scrap waste for treating the laboratory-made Ni²⁺-containing wastewater, the wastewater initially with ∼5600 ppm of Ni²⁺ ions could be reduced to ∼20 ppm in 2 h. When applying the Mg alloy flash scrap for the Ni plating wastewater from industry, the concentration of Ni²⁺ was able to be reduced from ∼16,670 ppm to ∼1434 ppm in 10 min for the wastewater at 90 °C.

Preparation of Mg(OH)2/Calcined Fly Ash Nanocomposite for Removal of Heavy Metals from Aqueous Acidic Solutions

A magnesium hydroxide (MH)-modified calcined fly ash (CFA) nanocomposite (CFAMH) with core-shell structure was obtained with a heterogeneous nucleation method, and its application for removal of copper, zinc and nickel ions from aqueous acidic solution was studied. The microstructure and surface properties of CFA, CFAMH and MH powders were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller specific surface area (BET), X-ray diffraction (XRD) and Fourier translation infrared spectroscopy (FTIR), respectively. The preparation mechanism of CFAMH was discussed based on zeta potential and FTIR data. The results showed that nano-flake MH with thickness 13.4 nm was well coated on the surface of CFA. The specific surface area was increased from 2.5 to 31.0 m²/g. Si-O-Mg-OH bonds formed from the condensation of Si-OH and Mg-OH. The removal efficiency of heavy metals on CFAMH nanocomposite is higher than that of CFA and MH and follows an order of Cu²⁺ > Zn²⁺ > Ni²⁺. Solubility product constant (Ksp) is an important constant for the removal order of heavy metals on FA, CFAMH and MH. CFAMH nanocomposite can be a cheap material for removing heavy metal ions from acidic wastewater.

Biogenic and chemically synthesized Solanum tuberosum peel-silver nanoparticle hybrid for the ultrasonic aided adsorption of bromophenol blue dye

This work was aimed at the synthesis of a hybrid (STpe-AgNP), obtained by impregnation of silver nanoparticles (AgNP) onto Solanum tuberosum peel (STpe), for the ultrasonic assisted adsorption of bromophenol blue (BB) dye. SEM, FTIR, XRD, EDX, TGA and BET techniques were used to characterize the adsorbents. The XRD, SEM and EDX confirmed successful impregnation of AgNPs onto STpe to form the hybrid. The AgNPs impregnated onto the hybrid were found to be water stable at various pH values of 2.0-9.0. Chi-square (χ2 < 0.024) and linear regression (R2 > 0.996) showed that the Freundlich model was best fitted among the isotherm models, corroborated by the oriented site model. Kinetic analysis conformed to the intraparticle diffusion and pseudo-first-order rate equations, while thermodynamics displayed a physical, spontaneous and endothermic adsorption process. The presence of competing Pb(II), Ni(II), Cd(II) and Zn(II) metal ions in solution interfered with the adsorption of BB onto the biosorbents. In terms of reusability, STpe and STpe-AgNP showed BB desorption of 91.3% and 88.5% respectively, using NaOH as eluent. Ultra-sonication significantly enhanced the adsorption of BB by both adsorbents, but the impregnation of AgNPs only slightly improved adsorption of the dye from the simulated wastewater. This study also illustrated that pristine STpe biomass waste is a cheap viable option for the decontamination of BB from water.

Studies on the Potential of Nonmodified and Metal Oxide-Modified Coal Fly Ash Zeolites For Adsorption of Heavy Metals and Catalytic Degradation of Organics for Waste Water Recovery

A nanocrystalline zeolite of Na-X type (CFAZ) was synthesized by ultrasonic-assisted double stage fusion-hydrothermal alkaline conversion of lignite coal fly ash. Modified CFAZ with magnetic nanoparticles (MNP-CFAZ) was obtained by adding presynthesized magnetic nanoparticles between the synthesis stages. CFAZs loaded by particles of copper (Cu-CFAZ) and cobalt (Co-CFAZ) oxides were prepared by postsynthesis modification of the parent CFAZ, applying a wet impregnation technique. The parent and modified CFAZs were examined for their phase composition by X-ray diffraction, morphology by scanning electron microscopy, and surface characteristics by N2 physisorption. Comparative studies have been carried out on the adsorption capacity of the starting CFAZ and its derivatives with respect to Cd2+- and Pb2+-ions from aqueous solutions. Adsorption isotherms of Cd2+-ions on the studied samples were plotted and described by the adsorption equations of Langmuir, Freundlich, Langmuir–Freundlich, and Temkin. The best correlation between the experimental and model isotherms for the parent and modified CFAZ was found with the Langmuir linear model, assuming a monolayer adsorption mechanism. Parent and modified CFAZs were also studied as catalysts for heterogeneous thermal Fenton oxidation of methylene blue. At 90 °C, the higher catalytic activity exhibits the nonmodified sample, but with the decrease in temperature to 60 °C, the modified samples are more effective catalysts.