Modified Coal Fly Ash Research Articles

Adsorption study of modified coal fly ash with sulfonic acid as a potential adsorbent for the removal of toxic reactive dyes from aqueous solution: Kinetics and thermodynamics

Great emphasis is being put in to develop green, efficient and inexpensive adsorbent in recent years. In this study, we demonstrate the potential of coal fly ash (CFA) materials as environmental pollutant adsorbent. The Sulfonic acid functionalized heat and alkali treated CFA (HATF-SO3H), is synthesized by condensation of 3-mercaptopropyltrimethoxysilane (3-MPTS) and heat and alkali treated CFA (HATF) followed by oxidation of surface thiol groups by H2O2 to sulfonic acid groups. The as-synthesized product is used to remove toxic and reactive dyes i.e. Malachite green (MG) and Rhodamine 6G (R6G), which are the main contaminant from the dye manufacturing and textile finishing. The efficiency of the dye adsorption on HATF-SO3H surface was investigated under various experimental parameter such as adsorbent dose, contact time, stirring speed, pH, and temperature. The proficient sorption efficacy of HATF-SO3H qm towards toxic and reactive dyes (efficiency of MG removal, 99.20%; maximum specific removal qm 233.30 mg g−1: efficiency of R6G removal, 98.70%; maximum specific removal 381.70 mg g−1) can be explained from the perspective of both electrostatic and H-bonding interactions between the surface of HATF-SO3H and dye molecules.

Methylene blue adsorption properties of mechanochemistry modified coal fly ash

ABSTRACTIn this study, the adsorption properties of Methylene blue (MB) on fly ash were investigated. By mechanochemistry modification, two different fly ashes, including raw fly ash and high-energy ball milled fly ash were selected for the adsorption experiment. The physical and morphology properties after the milling process were analyzed using mercury intrusion porosimetry, scanning electron micrograph, X-ray diffraction, and Fourier transform infrared spectroscopy. The results showed that the milling process modification will enhance the MB adsorption capacity of fly ash, with the value of adsorption capacity increasing from 5.06 to 7.97 mg g−1. The adsorption can be well described by the pseudo-second-order rate model. The results of this study indicated that the milled fly ash has the potential to be an attractive material for dye removal from aqueous solution. Meanwhile, some pollutants in fly ash should be considered before application.

Modified coal fly ash as low cost adsorbent for removal reactive dyes from batik industry

The removal of reactive dyes on modified coal fly ash has been investigated during a series of batch adsorption experiments. Physical characteristics of modified coal fly ash was characterized by Brunauer Emmett Teller (BET) surface area analysis, X-ray powder diffraction (XRD), Fourier transform infrared spectrophotometer (FT-IR), and scanning electron microscope (SEM). The effects of operational parameters such as initial dye concentration (50–200 mg/L), solution pH (4–10) and adsorbent dosage (50–200 mg/L) were studied. The adsorption experiments indicated that modified coal fly ash was effective in removing of Remazol Blue. The percentage removal of dyes increased while the modified fly ash dosage increased. The percentage removal of dyes increased with decreased initial concentration of the dye and also increased with amount of adsorbent used. The optimum of removal of dyes was found to be 94% at initial dye concentration 50 g/mL, modified fly ash dosage 250 g/mL, and pH of 2.0.

Phosphate removal from industrial wastewater effluent using modified coal fly ash

Phosphate removal from industrial wastewater effluent using modified coal fly ash

Enhancement of cationic polyacrylamide conditioning of sewage sludge with modified coal fly ash

Enhancement of cationic polyacrylamide conditioning of sewage sludge with modified coal fly ash

Preparation, characterization and sludge conditioning performance of modified coal fly ash

Filtration aids have been widely used in improving sludge dewatering performance, while the previous filtration aids have relatively lower efficiency in adsorption and bridging ability. In this study, a modified coal fly ash (MCFA) was prepared by soaking raw coal fly ash (RCFA) with sulfuric acid. Scanning electron microscopy (SEM), X-ray powder diffraction (XRD), Specific Surface Area and Pore Size Analyzer (BET) and X-ray photoelectron spectroscopy (XPS) were utilized to characterize its structure and morphology. The sludge conditioning performance and dewatering performance on secondary sludge was carried out based on the specific resistance to filtration, capillary suction time and LB-EPS protein content analysis. It showed that the optimum conditions for preparing MCFA from RCFA was a soaking time of 2h, the acid concentration of 5.0mol/L and the ratio of acid to RCFA 5:1, under which MCFA exhibited a higher efficiency in sludge conditioning. XRD analysis revealed a high proportion of silicon in MCFA at ca. 26.80%, whereas XPS implied that more silicon was grafted onto the Si–O structure. SEM and BET measurements indicated that the surface of MCFA had underwent a strong corrosion, exhibiting a larger surface area, high pore volume and small average particle size, which had promoted its adsorption capacity and permeability in aiding sludge dewatering.

Microwave radiation improves biodiesel yields from waste cooking oil in the presence of modified coal fly ash

This paper studied the effects of using modified coal fly ash as a catalyst to convert waste cooking oil (WCO) into biodiesel under microwave-strengthened action. Coal fly ash was modified with sodium sulphate and sodium hydroxide, and the obtained catalyst was characterized using FT-IR and X-ray diffraction (XRD). The experimental results showed that the modified coal fly ash catalyst improved biodiesel yields under the microwave-assisted system, and the maximum biodiesel yield from waste cooking oil reached 94.91% at a molar ratio of methanol to WCO of 9.67:1 with 3.99% wt% of modified coal fly ash catalyst (based on oil weight) at a 66.20°C reaction temperature. The reusability of the modified coal fly ash catalyst was excellent, and the conversion yield remained greater than 90% after the catalyst was reused 8 times. The produced biodiesel met the main parameters of the ASTM D-6751 and EN14214 standards.

Fabrication and Application of Low-Cost Thiol Functionalized Coal Fly Ash for Selective Adsorption of Heavy Toxic Metal Ions from Water

A novel thiol modified coal fly ash (CFA-SH) is successfully synthesized by a facile, efficient, and environmentally friendly process using 3-mercaptopropyltrimethoxysilane (MPTS). Various techniques have been used to characterize thoroughly the structure, the surface property, and the presence of the mercaptopropyl groups. The synthesized material proves to be an effective and selective adsorbent for removal of Hg2+ and Cd2+ ions from aqueous solution. The effect of time, pH, sample dose, speed, temperature, and metal ion concentrations were investigated thoroughly to optimize the sorption process. The kinetics data fitted in accordance with the pseudo-second-order model. It is also noticed that the Langmuir equation provides an accurate description of these sorption data, implying that monolayer sorption took place during adsorption. The quick and excellent uptake capacities (qm of 361.01 mg g–1 for Hg2+ within 50 min at pH 8 and 106.38 mg g–1 for Cd2+ within 60 min at pH 8) of the sorbent can be descri...

Catalytic oxidation of organic pollutants in wastewater via a Fenton-like process under the catalysis of HNO3-modified coal fly ash

Organic wastewater can be treated effectively via a heterogeneous Fenton-like process under the catalysis of HNO3-modified coal fly ash.

Fabrication of Inexpensive Polyethylenimine-Functionalized Fly Ash for Highly Enhanced Adsorption of Both Cationic and Anionic Toxic Dyes from Water

Polyethylenimine-based modified coal fly ash (CFA-PEI) is synthesized by the wet impregnation method. The material was found to be an excellent adsorbent for removal of cationic (Malachite Green; MG) and anionic (Reactive Red 2; RR2) dyes from aqueous solution. CFA-PEI was characterized by various sophisticated instruments such as FTIR spectroscopy, 13C MAS NMR spectroscopy, XRD, elemental analysis, Brunauer–Emmett–Teller (BET) isotherm, TGA, FESEM, and HRTEM. The FTIR spectra reveal that the N-containing functional group is introduced on the surface of CFA-PEI, which plays a vital role in the removal of these dyes. The adsorption behavior of the CFA-PEI toward toxic dyes is evaluated by investigating the effect of solution pH, contact time, solution temperature, adsorbent dose, and concentration of dye solution. The obtained adsorption isotherm and the kinetics data of both MG and RR2 are in compliance with the Langmuir adsorption isotherm and pseudo-second-order kinetics, respectively. Moreover, excelle...

Comparison of adsorption of Cd(II) and Pb(II) ions on pure and chemically modified fly ashes

Abstract The study investigates chemical modifications of coal fly ash (FA) treated with HCl or NH4HCO3 or NaOH or Na2edta, based on the research conducted to examine the behaviour of Cd(II) and Pb(II) ions adsorbed from water solution on treated fly ash. In laboratory tests, the equilibrium and kinetics were examined applying various temperatures (293 - 333 K) and pH (2 - 11) values. The maximum Cd(II) and Pb(II) ions adsorption capacity obtained at 293 K, pH 9 and mixing time 2 h from the Langmuir model can be grouped in the following order: FA-NaOH > FA-NH4HCO3 > FA > FA-Na2edta > FA-HCl. The morphology of fly ash grains was examined via small-angle X-ray scattering (SAXS) and images of scanning electron microscope (SEM). The adsorption kinetics data were well fitted by a pseudo-second-order rate model but showed a very poor fit for the pseudofirst order model. The intra-particle model also revealed that there are two separate stages in the sorption process, i.e. the external diffusion and the inter-particle diffusion. Thermodynamics parameters such as free energy, enthalpy and entropy were also determined. A laboratory test demonstrated that the modified coal fly ash worked well for the Cd(II) and Pb(II) ion uptake from polluted waters.

Ultrasound strengthened biodiesel production from waste cooking oil using modified coal fly ash as catalyst

This paper investigated the effects of modified coal fly ash as catalyst on the waste cooking oil (WCO) conversion into biodiesel under ultrasound strengthened action. Experimental results showed that the modified coal fly ash catalyst could improve biodiesel yields under ultrasound assisting system, and the maximum biodiesel yield from waste cooking oil reached 95.57% under a molar ratio of methanol to WCO of 10.71:1, a 4.97wt% modified CFA catalyst (based on oil weight), and a 1.41min reaction time. The reusability of the modified coal fly ash catalyst was well, and the conversion yield was still higher than 90% after the catalyst was used for 8 times repeatedly.

Disintegration of excess sludge enhanced by a combined treatment of gamma irradiation and modified coal fly ash

Abstract In order to improve the disintegration performance and accelerate the disintegration rate of excess sludge, the individual and combined influences of γ-ray irradiation and modified coal fly ash treatment on the disintegration of excess sludge were investigated based on physicochemical properties of excess sludge. The changes in constituents of excess sludge were examined by means of UV/vis spectra and SEM images. The results showed that the disintegration performance of excess sludge was effectively improved by gamma ray irradiation in the presence of modified coal fly ash. A new band from 250 nm to 290 nm appeared on all irradiated sludge samples. The SEM images illustrated the cells surfaces of the sludge by the combined treatment were disfigured. The SCOD, soluble carbohydrate and protein from sludge supernatant increased obviously with increasing modified CFA dosage from 0 to 0.2 g ml −1 and dose from 0 to 10 kGy. The sludge SRF and filter cake moisture declined significantly, and the filtration speed was faster. In conclusion, γ-ray irradiation-modified coal fly ash pretreatment is an effective method to disintegrate excess sludge.

Removal of sulfonated humic acid from aqueous phase by modified coal fly ash waste: Equilibrium and kinetic adsorption studies

Sulfonated humic acid (SHA) is a representative organic pollutant in oilfield wastewater. This study investigated the performance of modified fly ash in removal of SHA from aqueous solution. Two types of raw fly ash, including Shand fly ash (class C) and BD fly ash (class F) were used. X-ray diffraction and surface area analyses were also implemented to characterize the change of fly ash after modification. The results showed suitable acid- and microwave-assisted modification could enhance adsorption capacity of fly ash. The efficiency for SHA removal by treated Shand fly ash was higher than that by treated BD fly ash under the same conditions. Among different factors, pH was the most critical factor which could influence the adsorption performance of treated fly ash. The SHA removal efficiency increased as modified fly ash dosage increased up to 1 and 6g/L for Shand and BD fly ash, respectively. Langmuir isotherm could better fit equilibrium data. Kinetic analysis results showed this process could be well described by pseudo-second-order model. There was higher adsorption capacity at higher temperature when temperature varied between 15 and 35°C. The addition of NaCl also had influence on the adsorption performance of modified fly ash. The results of this study can help reveal the interactions of SHA pollutant and fly ash characteristics, which have important implications for the application of adsorption technologies in the treatment of oilfield wastewater.

Treatment of Cr(VI) WasteWater with Modified Coal Fly Ash

In this work, modified fly ash by Na2CO3 was prepared and used to remove the Cr (VI) in simulate wastewater, which was rarely reported in domestic and foreign. In the meantime, every single-factor experiment, which maybe influenced the removal ratio of Cr (VI), was done. The major-minor order of test factors and the optimum combination processing conditions influencing the treatment effects of Cr (VI) were determined according to the orthogonal experiment. The results showed that the major-minor order was initial concentration of Cr (VI), dosage of modified fly ash, adsorption duration, temperature and pH values. And the optimum combination of above discussed factors was 15 mg/L, 5 g, 90 min, 30 oC and 2.5, respectively. Under this optimum condition, the removal rate of Cr (VI) can reach more than 74.86%, approximately 1.35 times compared to that of original fly ash.

Improving Dehydration Property of Elutriation Sludge by CPAM and Modified Coal Fly Ash

This article studied the dehydration effect of elutriation sludge produced in the process of cultivating aerobic granular sludge, which is a joint regulation of cationic polyacrylamide (CPAM) and modified coal fly ash, using sludge specific resistance(SRF) and moisture content of sludge extent as the target. The results show that the greater the relative molecular weight, the better effect is. CPAM whose relative molecular weight is 8 million is the best type when solo casted. When casted by15 mg/L, SRF is reduced to 0.43×108 S2/g, The 1 g/L coal fly ash and 15 mg/L 8 million CPAM joint control, SRF is reduced to 0.4×108 S2/g, moisture content is 72.04%. When using modified coal fly ash, the result is better. Modified coal fly ash can effectively promote the efficiency of CPAM as the coagulant aid. It can further reduce SRF and moisture content of the sludge. We can observe the effects modified coal fly ash joint CPAM has on elutriation sludge morphology by scanning electron microscopy (SEM).

Treatment of Phenol WasteWater with Modified Coal Fly Ash-Fenton Reagent

Autonomous coal fly ash modified by vitriol (H2SO4) was used to treat Phenol Waste Water. The treatment influences were determined by single-factor experiment and the prioritizing importance and optimizing combination of the influences were studied using orthogonal experiment. We found that the prioritizing importance of the influencing factors was as follow: dosage of ferrous sulfate (FeSO4) > dosage of hydrogen peroxide (H2O2) > initial concentration of phenol > PH > the dosage of modified coal fly ash. The optimizing combination of the influences was 5 wt.% FeSO4, 1 mL ; 3 wt.%H2O2, 7 mL; PH=5; initial concentration of phenol , 300 mg/L and the dosage of modified coal fly ash, 200 mg/L. Under the condition above, phenol removal rate was 99.46%.

Characterization of the surface and physical properties of South African coal fly ash modified by sodium lauryl sulphate (SLS) for applications in PVC composites

The application of coal fly ash as mineral filler in polymers is hampered by the aggregation of the ash particles and a lack of interaction between the ash and polymer. Therefore surface treatment is usually performed on mineral fillers to enhance workability and compatibility between the polymer and filler. In this study, a commercially available South African coal fly ash sample was surface modified under a variety of conditions with an anionic surfactant, sodium lauryl sulphate (SLS), with the aim to alter the surface properties of the ash. The properties of the modified products were compared to those of the untreated samples by means of scanning electron microscopy (SEM), transmission electron microscopy (TEM), thermogravimetric analysis (TGA-IR), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray fluorescence spectroscopy (XRF). A small shift of the SO stretch vibration in FTIR spectra of SLS treated fly ash is indicative of interaction between fly ash and SLS. Although the overall chemical composition of the SLS modified coal fly ash sample was not altered extensively, significant changes could be observed in its physical properties. Contact angle measurements indicated that the hydrophilic surface of untreated fly ash was rendered hydrophobic after SLS treatment. SEM and TEM results showed agglomerates on the surface of most of the fly ash spheres. Feasibility tests of using fly ash samples as filler in PVC indicated that SLS treated fly ash can successfully replace CaCO3 as filler in PVC under conditions of low filler loadings.

Experimental Study of Modified Coal Fly Ash Adsorption Properties on Ammonia-Nitrogen in Biogas Slurry

With the development of the biogas construction, a plenty of biogas slurry was generated. It brought destruction to the environment for the biogas slurry was rich in nutrient components, especially ammonia-nitrogen. Its important that biogas slurry should be treated before it returns to the environment. The zeolite is extensively used in ammonia-nitrogen adsorption for its good adsorption effect. In this study, a modified coal fly ash (CFA) which was produced from raw CFA and had similar structure with zeolite was used as the adsorbent to adsorb ammonia-nitrogen in biogas slurry. The optimum adsorption conditions of modified CAF on adsorbing ammonia-nitrogen in biogas slurry were explored. The results showed that the best conditions were: the mass of modified CAF 1.3g, the initial pH value of solution 5~7 and the adsorption time 20 min.

Removal of Natural Organic Matter of Artificial Lake by Modified Fly Ash

Coal fly ash (CFA) modified by sulfuric acid treatment was used as a low-cost adsorbent for removing natural organic matter (NOM) in an artificial lake. The specific surface areas and SEM images of modified coal fly ash (MCFA) and CFA were observed. Two equilibrium models were compared to evaluate NOM removal process with a better fitting using the Freundlich model. Kinetic studies were also carried out to fit the experimental data. The pseudo second-order provided the highest coefficients of determination.