A critical global issue in the 21st century is water shortage, as well as its pollution with noxious metal ions and organic dyes. To extract these pollutants from wastewater, a variety of traditional methods have been employed but they lack reusability/recyclability, are expensive, environmentally unfriendly, unsafe and the remediation process takes a long time. Therefore, to treat these contaminants, nanotechnology (NT) has recently been granted several leeways in terms of making the desirable nanomaterials (NMs) with high surface-to-volume ratios and special surface functionalities. In particular, fly ash (FA) has stood out as one of the greatest exciting new-found affordable and high efficient materials for water decontamination owing to its high porosity, huge surface area, and exceptional features. Hence, this present review study will attempt to compile data from existing literature on the utilization of FA-based adsorbent for the removal of heavy metals (HMs) and dyes from wastewater. Based on the reviewed publications, Langmuir's isotherm models (LIMs) and Freundlich's isotherm models (FIMs) best described the sorption process thus signalling monolayer and multi-layer sorptions. Pseudo-second-order (PSO) model provided the best appropriate means in elucidating the kinetic process and both exothermic and endothermic processes revealed the nature of the thermodynamic process during sorption. Some recommendations in the form of future prospects on how to advance the capacity of the adsorption and effectiveness of FA on the removal of HMs, dyes and other environmental contaminants using innovative technologies such as the nanofiber technology is also been proposed.

Fly ash-based adsorbent for adsorption of heavy metals and dyes from aqueous solution: a review

The current study reports the first use of Fe-ZSM-5 as a potential adsorbent for textile effluent purification. The Fe-ZSM-5 zeolite was synthesized through a hydrothermal method using tetrapropylammonium bromide as an organic structure-directing template for application as a binder for basic Fuchsin (BF) dye from aqueous media. SEM observations confirmed that Fe-ZSM-5 exhibits a granular shape with a quasi-hexagonal structure, which is in agreement with its crystallinity demonstrated by XRD analysis. FTIR analysis indicates the abundance of Si OH groups on the Fe-ZSM-5 surface. N2 adsorption-desorption measurement showed the microporous structure (pore size around 1.93 nm) of Fe-ZSM-5 with a BET surface area of 399 m2/g. The uptake performance of Fe-ZSM-5 zeolite for BF dye was systematically studied as a function of different operational parameters. The experimental adsorption data were in good agreement with pseudo-second-order kinetics and Langmuir isotherm with a maximum adsorbed amount of 251.87 mg/g. BF dye adsorption onto Fe-ZSM-5 was a spontaneous and endothermic phenomenon. The binding mechanism is attributed to electrostatic interactions combined with H-bonding. Further, the response surface modeling permits us to optimize BF dye adsorption process. The highest BF dye removal performance was found to be 99.6 % under optimum conditions of pH 5, Fe-ZSM-5 dose 0.75 g/L, initial BF concentration 10 mg/L for 120 min at 20 °C. The findings of this work revealed that Fe-ZSM-5 zeolite could be proposed as an alternative adsorbent with outstanding performance for BF dye removal from wastewaters.

Fe-ZSM-5 zeolite for efficient removal of basic Fuchsin dye from aqueous solutions: Synthesis, characterization and adsorption process optimization using BBD-RSM modeling

A review on accessible techniques for removal of hexavalent Chromium and divalent Nickel from industrial wastewater: Recent research and future outlook

Synthesis of zeolite from sugarcane bagasse fly ash and its application as a low-cost adsorbent to remove heavy metals

Graded synthesis of highly ordered MCM-41 and carbon/zeolite composite from coal gasification fine residue for crystal violet removal

Zeolite P synthesis based on fly ash and its removal of Cu(II) and Ni (II) ions

https://iopscience.iop.org/article/10.1088/2053-1591/aaea41/pdf

The thermodynamics and kinetics for the removal of copper and nickel ions by the zeolite Y synthesized from fly ash

Fly ash (FA) from coal-based thermal power plant was used to synthesize zeolite in NaOH solution with hydrothermal method in this work. Firstly, the effects of calcination and acid treatment on the removal of impurities in fly ash were studied. Then based on the pretreated FA, the effects of alkali concentration, reaction temperature and Si/Al ratio on the synthesis of zeolite were studied in detail. The mineralogy, morphology, thermal behavior, infrared spectrum and specific surface for the synthetic sample were investigated. The results indicated that calcination at 750 °C for 1.5 h can basically remove unburned carbon from FA, and 4 M hydrochloric acid treatment of calcined FA at 90 °C for 2 h will reduce the quality of about 34.3%wt, which are mainly iron, calcium and sulfur elements. The concentration of NaOH, reaction temperature and Si/Al ratio have important effect on the synthesis of zeolite. In this study, 0.5 M NaOH cannot obtain any zeolite. High temperature is beneficial to zeolite synthesis from FA, but easily lead to a variety of zeolites. The synthetic sample contains three kinds of zeolites such as zeolite P, sodalite and zeolite X, when the reaction conditions are 2 M NaOH and 120 °C for 24 h. In this research, quartz always exists in the synthetic sample, but will reduce with the increase of temperature. The synthetic zeolite has the specific surface area of about 42 m2 g−1 and better thermal stability.

https://iopscience.iop.org/article/10.1088/2053-1591/aac3ae/pdf

Synthesis and characterization of zeolite from coal fly ash

https://iopscience.iop.org/article/10.1088/2053-1591/ab4e45/pdf

The influencing factors of hydrothermal synthesis of ZSM-5 zeolite and its adsorption of phenol, quinoline and indole

The invention relates to a method for synthesizing HZSM-5 type zeolite by pulverized fuel ash. The method is characterized in that the pulverized fuel ash is subjected to grinding sieving, alkali fusion and acid dissolution treatment under the boiling condition; a pretreatment product with the obviously improved silica alumina ratio is obtained; then, a certain quantity of water and template agents are added into the product; after uniform stirring is performed, the solution pH is regulated by sodium hydroxide; aging is performed for a period of time under the room temperature condition; high-quality HZSM-5 type zeolite is synthetized through hydrothermal reaction. The method has the advantages that the operation is simple and convenient; the resource utilization of solid waste of pulverized fuel ash is realized; the synthesized zeolite product is single crystalline phase HZSM-5 type zeolite; the crystallinity degree is greater than 95 percent; the purity is greater than 98 percent; good hexagonal prism feature morphology is realized.

Qiong Luo

Papers

Zeolite P synthesis based on fly ash and its removal of Cu(II) and Ni (II) ions

The thermodynamics and kinetics for the removal of copper and nickel ions by the zeolite Y synthesized from fly ash

Synthesis and characterization of zeolite from coal fly ash

The influencing factors of hydrothermal synthesis of ZSM-5 zeolite and its adsorption of phenol, quinoline and indole

Method for synthesizing HZSM-5 type zeolite by pulverized fuel ash