Ultrafast removal of Cu(II) by a novel hierarchically structured faujasite-type zeolite fabricated from lithium silica fume

Insights into the interaction between cadmium/tetracycline and nano-TiO2 on a zeolite surface

Titanium dioxide (TiO₂) nanoparticles interact with organic-inorganic pollutants in the environment, and these interactions affect their environmental behavior. The mechanisms of the interaction between TiO₂ and organic-inorganic pollutants on the surface of clay minerals are still unclear. In this work, isotherm adsorption was studied to explore the interactions between Cd²⁺/tetracycline (TC), TiO₂ nanoparticles, and a zeolite (Zeo). SEM, FT-IR, and XPS were also used to reveal the interaction mechanism between organic-inorganic pollutants and TiO₂ on their stability and mobility in the environment. Compared to the single systems, the adsorption of Cd²⁺ and TiO₂ in the Cd + TiO₂ composite system decreased by 3.43% and 9.90%, respectively; the TC and TiO₂ adsorption in the TC + TiO₂ composite system decreased by 14.39% and 45.47%, respectively. The antagonism between Cd²⁺ and TiO₂ was due to Cd²⁺ and TiO₂ competing for the electrostatic attraction (-OH) and hydrogen bonding sites (Si-O), and TC and TiO₂ competing for the hydrogen bonding sites (-OH and C = O) on Zeo. The presence of TiO₂ will increase the mobility of Cd²⁺ and TC on a clay surface, and this effect is more significant for organic pollutants TC. Compared with Cd²⁺, TC has a more significant boosting impact on the TiO₂ mobility.

Synthesis of high-quality NaP1 zeolite from municipal solid waste incineration fly ash by microwave-assisted hydrothermal method and its adsorption capacity

The Si and Al in municipal solid waste incineration fly ash (MSWI FA) can be utilized for zeolite fabrication, which can improve the application value of the products. This study focuses on the fabrication of zeolite from MSWI FA by microwave-assisted hydrothermal (MH) treatment. The effects of magnetic stirring time, Na₂SiO₃ dosage, MH time, and NaOH solution concentration on the crystallization of zeolite NaP1 from MSWI FA are systematically analyzed. The synthetic products are analyzed through spectroscopic and mineralogical methods. The results show that zeolite NaP1 with high crystallinity (51.68 %) can be fabricated by magnetic stirring and MH treatment, and the cation exchange capacity (CEC) of the product can reach a value of 2.58 meq/g, which is approximately 133 times that of the CEC of MSWI FA. The Si/Al ratio plays a decisive role in the zeolite NaP1 synthesis, and a Na₂SiO₃ dosage of 30 wt% is adopted for zeolite NaP1 fabrication. A NaOH concentration of 1 M is sufficient for zeolite NaP1 synthesis. Additionally, the zeolite NaP1 content is found to obviously increase with increasing MH time from 0.5 h to 2 h. To demonstrate the feasibility of the method provided in this study, the optimal experimental condition is employed for various MSWI FAs, and zeolite NaP1 and analcime are fabricated successfully. The leachability of heavy metals for the synthetic products was evaluated, which met the requirements for pollution control. The BET surface area and total pore volume of zeolite NaP1 fabricated at optimal condition are 61.42 m²/g and 0.44 cm³/g, respectively. The adsorption capacity of zeolite NaP1 for Cu²⁺ ion and methylene blue are determined to be 84.65 mg/g and 84.55 mg/g, respectively, indicating zeolite NaP1 is a potential adsorbent for cation ion and dyes. This study provides an environmentally friendly scheme for the utilization of MSWI FA.

A Mesoporous Faujasite Prepared by Space-Confined Method for Highly Effective Selectivity of Copper Ions

The discharge of copper ion (Cu(II)) into natural waters can lead to serious environmental and health problems; however, an abundantly porous hierarchical adsorbent, such as faujasite (FAU), can rapidly remove unwanted Cu(II). In this research, a hierarchically structured, abundantly mesoporous faujasite (FAU) was fabricated from industrial-waste lithium-silicon powder (LSP), with the addition of biochar and graphene oxide (GO) via hydrothermal synthesis without high-temperature calcination. The results demonstrated that just a small amount of biochar or GO can significantly improve the mesopore volume (0.14 cm³/g) and the Cu(II) adsorption capacity (115.65 mg/g) of composite FAU. In particular, careful examination of the properties of the composite FAU showed that the biochar and GO had favorably affected the growth of the zeolite crystals, thus promoting the formation of the FAU skeleton structure, ion-exchange sites and Si-OH. The composite FAU exhibited superior adsorption capacities and highly effective Cu(II) selectivity. Thus, the findings of this study provide a novel and cost-effective avenue for the synthesis of composite FAU with high copper-selective removal capacity.

Characterization of Cu(II) and Zn(II) Sorption onto Zeolite

In this study, a batch sorption study approach was combined with an instrumental analytical approach of atomic absorption spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) for the sorption of copper and zinc ions from aqueous solution on zeolites. Both copper and zinc are biogenic elements; nevertheless, many industrial processes produce an excessive amount, which is why their efficient removal from water must be studied. Two types of zeolites, Zeolite Micro 20 (Z-M20) and Zeolite Micro 50 (Z-M50), were used. The results showed that the maximum sorption capacities for removal of Cu and Zn were 1.06 for CuSO4, 42.35 for Cu(NO3)2, 1.15 for ZnSO4 and 2.29 for Zn(NO3)2 adsorption onto Z-M20 and 0.45 for CuSO4, 1.67 for Cu(NO3)2, 0.39 for ZnSO4 and 1.51 for Zn(NO3)2 adsorption onto Z-M50. The maximum sorption capacities are higher for sulfates and the sorbent with smaller particle size. The sorption capacities of Cu and Zn for corresponding anion and particle size differ only up to 5–15%. Using XRD and XPS analyses before and after the sorption process, it was found that the content of both Cu and Zn in the surface layer and the bulk are the same for sorption onto sorbent with smaller particle size, but are higher in the surface layer than in the bulk for sorption onto sorbent with larger particle size. One of the main findings of this study is that a zeolite with smaller particles takes Cu and Zn by the whole particle, while with bigger particles, Cu and Zn concentrate in the surface of the particle. The results of the study may be used as an indicator for sorption efficiency of the studied zeolites for their application in the treatment of copper and zinc contaminated effluents.

Low-cost Mn-Fe/SAPO-34 catalyst from natural ferromanganese ore and lithium-silicon-powder waste for efficient low-temperature NH3-SCR removal of NOx

The development of low-temperature selective catalytic reduction of NO_x with NH₃ (NH₃-SCR) catalysts is desirable but still challenging. Herein, a low-cost Mn-Fe/SAPO-34 catalyst was successfully synthesized using natural ferromanganese ore (FO) and industrial waste lithium-silicon-powder (LSP) by solid-state ion exchange (SSIE) method, and showed high NH₃-SCR activity at low temperature range (150-200 °C) with high N₂ selectivity. After loading FO, Mn-O and Fe-O bonds on Mn-Fe/SAPO-34 were weakened, which were beneficial to electron transfer and the oxidation-reduction cycle of SCR. The coexisting of Mn and Fe promoted the dispersion of Fe, resulted in high amounts of O_a, Mn⁴⁺ and Fe³⁺ which facilitated the adsorption and activization of NH₃ over Mn-Fe/SAPO-34 catalyst. The Brønsted and Lewis acid sites participate in NH₃-SCR, and the adsorbed nitrate species could quickly react with the adsorbed NH₃ species via the Langmuir-Hinshelwood (L-H) mechanism. The Mn-Fe/SAPO-34 integrated the advantages of low-cost, resource saving and environment friendly, giving a low-carbon and sustainable choice for the industrial application of NO_x abatement.

Preparation of a novel bio-adsorbent of sodium alginate grafted polyacrylamide/graphene oxide hydrogel for the adsorption of heavy metal ion

A novel bio-adsorbent named SA-PAM/GO hydrogel composites was synthesized through free radical polymerization. The structure and performance were characterized and analyzed by BET, SEM-EDS, FTIR and TGA. After modification, the BET surface area increased more than tripled, which was consistent with SEM results. Under optimal conditions, the maximum adsorption capacity of Cu²⁺ and Pb²⁺ were 68.76 mg/g and 240.69 mg/g, respectively. In addition, the research of kinetics and isotherms displayed that the pseudo-second-order kinetic model and the Langmuir isotherm model fitted the data well. After further research, the different adsorption mechanism including physical adsorption, chemical adsorption and electrostatic interactions were discussed. The chemical adsorption accompanying the ion exchange process was confirmed as the staple adsorption mechanism. Furthermore, the adsorbent still maintained good adsorption capacity after 5 cycles of adsorption-regeneration. Therefore, the SA-PAM/GO hydrogel composites have potential to remove the heavy metal ions from water body effectively.