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Using synthetic zeolite from fly ash to treat high concentration phosphorus wastewater does not only improve the utilization of fly ash as solid waste but also reduce the environmental pressure caused by eutrophication. A synthetic zeolite was prepared from coal fly ash by one-step hydrothermal synthesis and applied for phosphorus adsorption from industrial wastewater (∼8,000 mg-P/L), and its adsorption characteristics and performance were studied. The results indicated that the product was a well-crystallized Na-P1 zeolite with typical morphology of plate- and rod-shaped crystals. Compared with the original fly ash, the specific surface area and average pore volume of the synthetic zeolite were nine and six times larger than the fly ash, reaching 43.817 m2/g and 0.122 cm3/g. The results from phosphorus adsorption onto the synthetic zeolite showed that the synthetic zeolite had good phosphorus adsorption properties. The adsorption process highly conformed to the pseudo-second-order kinetic model with the regression coefficient R2 of 0.998. Phosphorus adsorption on the synthetic zeolite was fitted to the Langmuir monolayer adsorption model, and the regression coefficient R2 was 0.989. The maximum phosphorus adsorption capacity was 84.4 mg-P/g-zeolite. [ABSTRACT FROM AUTHOR]

The increasing requirement and consumption of coal has resulted in a large accumulation of coal gangue. The reuse and recycling of coal gangue have become a high priority for sustainable development. A sustainable and efficient ceramsite adsorbent was prepared for copper ions adsorption by using coal gangue, coal fly ash, and copper slag as the main materials. The appropriate performance of the ceramsite could be obtained at a mixture of coal gangue, coal fly ash, and copper slag at a weight ratio of 3:4:1. The optimal sintering temperature and time were 1050 °C and 20 min, respectively. The main crystalline phases of ceramsite were quartz, mullite, and anorthite. Many micropores are connecting the interior on the surface of ceramsite under scanning electron microscope. The maximum copper ions adsorption capacity reached up to 20.6 mg/g at 303 K when pH and time were 5 and 1440 min, respectively. The adsorption kinetics and isotherm could be described by the pseudo-second-order model and Freundlich model, respectively. The adsorption mechanisms of Cu2+ with ceramsite were attributed to Cu(OH) 2 precipitation formed on the alkaline surface of ceramsite and complexation reactions occurred between the O-containing groups (including C–O, Fe–O, and Si–O) from ceramsite and Cu2+. The prepared ceramsite may be also applied to other heavy metal wastewater treatments. • A green and efficient ceramsite adsorbent was prepared by industrial waste. • The adsorption capacity of copper ions with ceramsite was improved. • The adsorption kinetics could be described by the Freundlich model. • The adsorption mechanism of copper ions was studied deeply. [ABSTRACT FROM AUTHOR]

Directive, acid and reactive dyes are the carcinogenic dyes which have complex structures and difficult to remove from the industrial wastewater. In this study, coal fly ash (CFA) was modified with HCl and NaOH solution and used for the removal of direct fast scarlet 4BS, direct sky blue 5B, acid navy blue R, and reactive turquoise blue KN-G dyes. Laboratory experiments were carried out to analyze the performance of modified coal fly ash (MCFA) to check the removal efficiency and adsorption capacity of dyes. The maximum removal efficiency of direct fast scarlet 4BS and direct sky blue 5B were recorded 96.03% and 93.820%, respectively using 0.05 g adsorbent dosage at 100 mg/L initial concentration. The results of MCFA were compared with carbon black, chitosan, starch, zeolite and unmodified coal fly ash (UMCFA) at lower dosage 0.05 g and higher dosage 0.4 g. Adsorption isotherm were analyzed by Langmuir and Freundlich model by different dyes concentrations, the result stated that Freundlich and Langmuir model (±0.9918, ±0.9974) was fitted by chemisorption and physisorption methods for all four dyes. Adsorption kinetic were also determined by Pseudo-first-order and Pseudo-second-order at different contact times with dye molecules and adsorbent active sites, and the results showed that the adsorption behaviors of all four dyes were described better by pseudo-second-order kinetics than pseudo-first-order kinetics. Recommended dosage of modified fly ash is between 10 ‱ to 20 ‱ for simulated textile industrial waste water and regeneration temperature is 300 ℃. [Display omitted] • Coal fly ash was modified by HCl and NaOH for the dye adsorption. • After modification the surface area and porosity of CFA were increased. • Modified coal fly ash was used for the removal of directive, acid and reactive dyes. • Maximum removal efficiency of directive dye was recorded up to 98% by using modified CFA. • The results of MCFA were compared with carbon black, chitosan, starch, zeolite and unmodified coal fly ash. [ABSTRACT FROM AUTHOR]