Treated residue from aluminium lamination as adsorbent of toxic reactive dyes - a kinetic, equilibrium and thermodynamic study

Removal of p-Nitrophenol by Adsorption with 2-Phenylimidazole-Modified ZIF-8

Petrochemical wastewater contains p-nitrophenol, a highly toxic, bioaccumulative and persistent pollutant that can harm ecosystems and environmental sustainability. In this study, ZIF-8-PhIm was prepared for p-nitrophenol removal from petrochemical wastewater using solvent-assisted ligand exchange (SALE) with 2-phenylimidazole(2-PhIm). The ZIF-8-PhIm's composition and structure were characterised using the XRD, SEM, FT-IR, ¹H NMR, XPS and BET methods. The adsorption effect of ZIF-8-PhIm on p-nitrophenol was investigated with the static adsorption method. Compared to the ZIF-8 materials, ZIF-8-PhIm exhibited stronger π-π interactions, produced a multistage pore structure with larger pore capacity and size, and had increased hydrophilicity and exposure of adsorption sites. Under optimised conditions (dose = 0.4 g/L, T = 298 K, C₀ = 400 mg/L), ZIF-8-PhIm achieved an adsorption amount of 828.29 mg/g, which had a greater p-nitrophenol adsorption capacity compared to the ZIF-8 material. The Langmuir isotherm and pseudo-second-order kinetic models appropriately described the p-nitrophenol adsorption of ZIF-8-PhIm. Hydrogen bonding and π-π interactions dominated the p-nitrophenol adsorption of ZIF-8-PhIm. It also had relatively good regeneration properties.

The Synthesis of Magnetic Nitrogen-Doped Graphene Oxide Nanocomposite for the Removal of Reactive Orange 12 Dye

Herein, we report the nanofabrication of magnetic calcium ferrite (CaFe2O4) with nitrogen-doped graphene oxide (N-GO) via facile ultrasonication method to produce CaFe2O4/N-GO nanocomposite for the potential removal of reactive orange 12 (RO12) dye from aqueous solution. The successful construction of the nanocomposite was confirmed using different characterization techniques including scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform-infrared spectroscopy (FT-IR), and X-ray diffraction (XRD). The magnetic properties were studied using vibrating sample magnetometer (VSM) indicating ferromagnetic behavior of the synthesized materials that facilitate their separation using an external magnetic field after adsorption treatment. The addition of N-GO to CaFe2O4 nanoparticles enhanced the BET surface area from 24 to 52.93 m2/g as resulted from the N2 adsorption-desorption isotherm. The adsorption of the synthesized nanomaterials is controlled by several parameters (initial concentration of dye, contact time, adsorbent dosage, and pH), and the RO12 dye removal on the surface of CaFe2O4 nanoparticles and CaFe2O4/N-GO nanocomposite was reached through the chemisorption process as indicated from the kinetic study. The adsorption isotherm study indicated that the adsorption process of RO12 dye was best described through the Langmuir isotherm approving the monolayer adsorption. According to the Langmuir model, the maximum adsorption capacity for RO12 was 250 and 333.33 mg/g for CaFe2O4 nanoparticles and CaFe2O4/N-GO nanocomposite, respectively. The adsorption capacity offered by CaFe2O4/N-GO nanocomposite was higher than reported in the literature for adsorbent materials. Additionally, the regeneration study indicated that CaFe2O4/N-GO nanocomposite is reusable and cost-effective adsorbent. Therefore, the nanofabricated CaFe2O4/N-GO hybrid material is a promising adsorbent for water treatment.

Removal of textile dyes by benefited marine shells wastes: From circular economy to multi-phenomenological modeling

Marine shell wastes were thermally activated and characterized as aragonite and calcite phases and were used in the removal of synthetic anionic dyes, Bright Blue Acid (NB180) and Reactive Red 133 (RR133). Benefited marine shells were classified as low-cost (USD 0.33/g of adsorbent) in comparison with other reported materials. Furthermore, the absence of chemicals in the adsorbent preparation allows its further employment in economic activities. The coexistence of adsorption and exchange-precipitation reaction was responsible for up to 93% of dye removal, whilst the maximum adsorption capacities were 225 mg g^-1 for NB180 and 36 mg g^-1 for RR133. The observed kinetic behavior of the dye removal by the adsorbent allowed the proposal of a mechanism for dye-adsorbent interaction in liquid-solid interface considering both adsorption and exchange-precipitation reaction. Contribution of the exchange-precipitation reaction in the removal process was quantified as being approximately 75% for NB180 and 25% for RR133. The mathematical model that phenomenologically described the kinetic behavior of the dye removals gave the magnitude order of the kinetic parameters as k_ads = 8.67-9.49 min^-1 and k_p = 1.18-2.84 min^-1, due to the adsorption and the (exchange-reaction)-precipitation, respectively. This work indicates the step (exchange reaction)-precipitation as an additional contribution to improve the dye removal from aqueous effluents, achieving in the evolution of the process up to 24% in terms of kinetic selectivity of removal.

Resource Recycling of Mn-Rich Sludge: Effective Separation of Impure Fe/Al and Recovery of High-Purity Hausmannite

Groundwater treatment sludge is a Fe/Mn-rich waste generated in mass production in a groundwater treatment plant for potable water production. The conventional disposal of sludge, such as direct discharge into river/lake, sea, and landfill, is not environmentally sustainable. Herein, a novel method was proposed to effectively separate Fe/Al and recover Mn via a combined hydrochloric acid leaching and hydrothermal route. The sludge contained 14.6% Fe, 6.3% Mn, and 11.5% Al and was first dissolved in 5 M HCl to prepare a leaching solution. Second, the leaching solution was hydrothermally treated, in which 97.1% Fe and 94.8% Al were precipitated as hematite and boehmite and more than 98% Mn was kept. Increasing the reaction temperature to 270 °C was beneficial for Fe/Al removal. With the consumption of abundant H+, the reaction of added glucose and nitrate accelerated as the temperature increased. An optimal pH was utilized for Fe/Al hydrolysis and crystallization, leading to extensive removal of Fe/Al. Third, the residual solution was adjusted to pH 8.3 with NaOH, and approximately, 99.2% Mn was removed as hausmannite with a Mn content of 63.6%. This method exhibited efficient separation of impure Fe/Al from Mn-rich groundwater treatment plant iron mud, and the recycled high-purity hausmannite was a marketable active pharmaceutical ingredient.

Promoting adsorption of organic pollutants via tailoring surface physicochemical properties of biomass-derived carbon-attapulgite

Biomass-derived carbon-attapulgite adsorbent was developed for organic pollutants removal. All the batch assays were performed to evaluate the effects of organic components, contact time, and initial concentration of organic pollutants on the adsorption performance of the as-prepared adsorbent. The samples were characterized via Brunauer-Emmett-Teller (BET), Fourier transform infrared (FTIR), X-ray diffractometer (XRD), and scanning electron microscopy (SEM). The results demonstrated that the acid-treated carbon-attapulgite adsorbent (H-ATP/BC) showed a large specific surface area (237 m² g^-1) and possessed abundant oxygen-containing functional groups and silicon-oxygen bonds (i.e., O-Si-O and O-Si), which provided more active sites and conduced to the adhesive of organic pollutants. Both physical adsorption and chemical adsorption were involved in the adsorption process, and competitive adsorption occurred when two or more target pollutants coexist. Especially, phenol and/or aniline with an aromatic ring were much more likely to adhere to the H-ATP/BC surface than pyridine, and the selectivity order of H-ATP/BC for these pollutants was phenol > aniline > pyridine. From the model fitting, it was observed that the adsorption data could be described well by a pseudo-second-order model and Freundlich isotherms. The theoretical maximum phenol, aniline, and pyridine adsorption capacities of the H-ATP/BC were 14.31 mg g^-1, 15.21 mg g^-1, and 20.74 mg g^-1, respectively. Comparison among the commercial adsorbents price also illustrated that H-ATP/BC could be a promising material for efficient treatment of organic pollutants.Graphical abstract.

Effect of bifunctional acid on the porosity improvement of biomass-derived activated carbon for methylene blue adsorption

Activated carbon (AC) with high specific surface area was prepared by using bifunctional H₃PO₄ agent, which led to dehydrating and activation effects through hydrothermal pretreatment and subsequent pyrolysis process. N₂ adsorption and desorption isotherms of AC showed a high BET surface area of 2434 m² g^-1 and a total volume of pores (V_T) of 2.0447 m³ g^-1 for AC. The morphology and the chemical components of hydrochar and AC were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy, which indicated that H₃PO₄ was benefitting for the formation of porous structure of AC. Subsequently, the effect of H₃PO₄ in hydrothermal pretreatment and activation process was investigated by comparative experiments. The removal and adsorption of methylene blue (MB) dye with different concentrations onto the AC were studied. The monolayer equilibrium adsorption capacity was 644 mg g^-1, showing that AC has good adsorption qualities for methylene blue (MB). The adsorption balance data of MB on AC was best fitted to the Redlich-Peterson model. The adsorption kinetic data fit better to the pseudo-first-order model at low MB concentration, and the pseudo-second-order and Elovich models fit better when the MB concentration was rising.

Removal of azo dye from water via adsorption on biochar produced by the gasification of wood wastes

It was the aim of this work to evaluate the adsorptive performance of the biochar obtained from the gasification of wood residues onto a solution of Indosol Black NF1200 dye. The study was performed by means of factorial design 2², having as control variables: pH and adsorbent's granulometry. Batch tests were carried out at 200 rpm for 3 h (T = 28 °C). As output variable, the percentage removal of dye was determined. The best operating conditions were pH = 2 and 100 mesh granulometry. Also, adsorbent dosage studies were carried out, as well as equilibrium and adsorption kinetics. Both kinetics and equilibrium of adsorption tests were proceeded in basic and acid medium. For a basic pH value (pH = 12), it was concluded the equilibrium was reached in about 3 h of experiment, the experimental q_max value was near 12 mg g^-1, and the equilibrium data fitted the Langmuir model. On the other hand, for tests with pH = 2, the equilibrium was reached after 5 min of experiment, the experimental q_max value was over 185 mg g^-1, and the equilibrium data fitted both the Langmuir and Freundlich models. Thus, the biochar produced via gasification of wood wastes appears to be a promising adsorbent for the removal of azo dyes from textile wastewater, especially when working at lower pH values. Also, for a 10-kg/h consumption of wood residue, approximately 10 kW of energy is generated and 1 kg of biochar is produced, which represents another advantage from the environmentally friendly point of view. Graphical abstract.