Studies on the adsorption of dyes, Methylene blue, Safranin T, and Malachite green onto Polystyrene foam

Interaction behavior, mechanisms and hazardous changes of microplastics on single and binary component pesticide in the environment and food: Diethofencarb and pyrimethanil

In order to investigate the adsorption behavior and mechanism of microplastics (MPs) on multiple coexisting pesticides in practical systems, as well as their hazardous changes upon binding, diethofencarb and pyrimethanil were selected to be studied with four MPs. The adsorption rate of both pesticides would be faster in the binary-component case, conforming to pseudo-second-order kinetics, with adsorption sites and chemical adsorption dominating. And the more hydrophobic the pesticide, the faster the adsorption rate and the higher the adsorption capacity. Diethofencarb belonged to monolayer adsorption, whereas pyrimethanil belonged to monomolecular combined with multilayer adsorption, depending on the size of pesticides. And the adsorption process was both competitive and synergistic when pesticides coexist. In addition, the adsorption process was a spontaneous heat absorption process. Electrostatic forces have little effect on adsorption, while the adsorption capacity can be altered by the adsorption sites and hydrophobicity of MPs. The salting-out effect also facilitated the adsorption process. As for changes in hazard, the bioluminescence of A. fischeri wasn't significantly inhibited, lacking of acute environmental toxicity. However, in vitro digestion experiments demonstrated a significant increase in bioavailability of diethofencarb and pyrimethanil in combination with MPs. These findings suggest the stronger adsorption behaviors and higher loading capacities between pesticides and MPs could lead more serious hazards to the human body, which deserves further attention.

A comparative study on the malachite green dye adsorption of chemically synthesized and green MgFe2O4 nanoparticles using gerbera floral waste extract

The situation of discharging a large amount of dyes from the textile industries has caused many adverse effects on human health and the ecosystems. Emerging bio-nanomaterials represent a new trend in efficient dye removal in aqueous media. Herein, we mention that MgFe2O4 bioprepared using gerbera extract has been successfully used to adsorb malachite green (MG) in water. A comparison was made to determine the dye removal efficiency between biogenic MgFe2O4 (MFOB) and chemical MgFe2O4 (MFOC). The spherical MFOB material exhibited a large surface area of 85.0 m2 g-1 and high crystallinity. The obtained outcomes showed that the highest adsorption capacity of MG dye was 584.49 mg g-1 at a MFOB dose of 0.05 g L-1 and MG concentration of 10 mg L-1. Higher correlation coefficients in the Langmuir isotherm suggested monolayer adsorption of MG. The Box-Behnken design and response surface method were established to optimize MG removal percentage under the conditions, i.e., initial MG concentration (10-30 mg L-1), adsorbent dose (0.02-0.08 g L-1), and pH of dye solution (6-8). MFOB had good reusability with high removal efficiencies after three continuous cycles. Post reuse, this adsorbent still showed excellent stability through the verification of their structural properties in comparison with fresh MFOB, showing potential for practical applications.

The influence of electrolytes in the adsorption kinetics of reactive BF-5G blue dye on bone char: a mass transfer model

The discharge of harmful dyes in water bodies is a serious pollution problem, dangerous for the ecosystem's equilibrium and human health. In this sense, the aim of this work was to determine the influence of electrolytes (NaCl, KCl, CaCl2 and MgCl2) in the adsorption of Reactive Blue BF-5G dye, the most common dye used in industrial process for fabric colouring, using bovine bone char as the adsorbent. The bovine bone char was characterized by pH of point of zero charge (pHPZC), N2 adsorption-desorption isotherms, Fourier transform-infrared spectroscopy (FT-IR) and X-ray diffractometry (XDR). The characterization revealed a mesoporous structure (pore mean diameter of 94 Å and SBET ∼107 m2 g-1) with negative charge distribution at the surface (pHPZC = 3.8). The adsorption experiments revealed that the presence of KCl enhanced the material adsorption capacity (qmax = 195 mg g-1), that the Sips isotherm best fitted the experimental data (R2 > 0.9 except for KCl solution) and the adsorption process was mono- and multilayered. The kinetic adsorption experiments indicated that the inorganic electrolytes increased the initial adsorption velocity and the data was best modelled by the surface diffusional model (SDM), implying a resistance (aqueous > CaCl2 > NaCl > MgCl2 > KCl) to mass transfer at the surface of the pores which, in turn, prevented the dye diffusion to the interior of the adsorbent (qe = 71 mg g-1). Therefore, small quantities of KCl can be used to lower the mass transfer resistance and provide higher adsorption capacity with reduced time of operation, thus increasing the overall process efficiency.

Conversion of Waste Expanded Polystyrene into Blue-Emitting Polymer Film for Light-Emitting Diode Applications

The wide range of applications and continuous demand for plastics is causing serious global environmental problems. Massive discharges of expanded polystyrene (EPS) are thought to be primarily responsible for the increased white pollution. Waste EPS has received wide attention in the development of innovative products. White light-emitting diodes pumped by a near-UV chip (n-UV WLEDs) are regarded as a very promising solid-state lighting. The performance of the n-UV WLED is largely determined by the properties of the tricolor luminescence materials. In this work, a blue-emitting polymer film for n-UV WLED applications was developed from waste EPS. First, using waste EPS as a raw material, benzimidazole groups were bonded to PS benzene rings by chemical reactions to obtain modified PS (PS-PBI). Then, a film based on PS-PBI was prepared by a simple solution drop-casting method. The PS-PBI film can emit intense blue light when irradiated with 365 nm light. An n-UV WLED pumped by a 365 nm UV chip was fabricated using PS-PBI film as the blue-emitting layer. The fabricated n-UV WLED shows excellent luminescence properties, such as a bright white light with color coordinates of (0.337, 0.331), a relatively low color temperature (CCT, 5270 K), and an especially high color rendering index (CRI, 93.6). The results prove that the blue-emitting PS-PBI film prepared from waste EPS is a very promising candidate for n-UV WLED applications. The strategy of converting waste EPS into a high-value-added blue-emitting film in this work provides a convenient and feasible approach for upcycling waste EPS, achieving significant environmental and economic benefits.

Comparing the adsorption of methyl orange and malachite green on similar yet distinct polyamide microplastics: Uncovering hydrogen bond interactions

Microplastics (MPs) and dye pollutants are widespread in aquatic environments. Here, the adsorption characteristics of anionic dye methyl orange (MO) and cationic dye malachite green (MG) on polyamide 6 (PA6) and polyamide 66 (PA66) MPs were investigated, including kinetics, isotherm equilibrium and thermodynamics. The co-adsorption of MO and MG under different pH was also evaluated. The results reveal that the adsorption process of MO and MG is suitably expounded by a pseudo-second-order kinetic model. The process can be characterized by two stages: internal diffusion and external diffusion. The isothermal adsorption equilibrium of MO and MG can be effectively described using the Langmuir model, signifying monolayer adsorption. Furthermore, the thermodynamic results indicated that the adsorption was spontaneous with exothermic and endothermic properties, respectively. The results of binary systems reveal that MO dominates the adsorption at low pH (2-5), while MG dominates at high pH (8-10). Strong competitive adsorption was observed between MO and MG in neutral conditions (pH 6-8). The desorption experiments confirm that PA6 and PA66 could serve as potential carriers of MO and MG. The interaction between dyes and polyamide MPs is primarily mediated through hydrogen bonds and electrostatic attraction. The results reveal that PA6 formed more hydrogen bonds with the dyes, resulting in higher adsorption capacity than that of PA66. This difference can be attributed to the disparities in the synthesis process and polymerization method. Our study uncovered the adsorption mechanism of dye pollutants on PA6 and PA66, and provided a more comprehensive theoretical basis for the risk assessment concerning different types of polyamide MPs in aquatic environments.

Efficient removal of cationic dye using ZIF-8 based sodium alginate composite beads: Performance evaluation in batch and column systems

The environmental and health risks associated with dye contamination in water sources are alarming. Recently, researchers have been focusing on developing an innovative and susceptible solution using composite beads that effectively combat this issue. In this paper, beads were synthesized using a sodium alginate (SA) and zeolitic imidazolate framework-8 (ZIF-8) through a simple dipping process. Several characterization tests were performed including XRD, FTIR, BET, TGA, and SEM-EDX. The SEM images confirmed that SA effectively coated the cubical structure of the ZIF-8, ensuring optimal performance. The efficiency of the resulting SA@ZIF-8 composite beads was tested on both synthetic malachite green dye and real industrial wastewater samples using batch and fixed bed column reactors. The findings revealed that maximum adsorption of 95.5% was achieved at pH 6 in 120 min of reaction time. FTIR and SEM analysis also confirmed the adsorption of MG dye onto the beads. The Freundlich isotherm model (R2 > 0.99) has a better fit than the Langmuir (R2 > 0.96) for describing the adsorption process. The PSO model predicted the kinetics of the system, whereas the intraparticle diffusion study supported the system's mechanistic analysis. Furthermore, the study also investigated the efficacy of the beads in treating real wastewater effluent samples collected from the dye industry. Overall, using sodium alginate-coated ZIF-8 beads was found to have many advantages over powdered ZIF-8, including higher selectivity, stability, reusability, and practicality, making them a promising alternative for adsorption applications. Therefore, these composite beads have the potential for the removal of the dye from wastewater, which could be widely applied in various industries.

Characterization of the microbial community and prediction of metabolic functions in an anaerobic/oxic system with magnetic micropolystyrene as a biocarrier

Polystyrene (PS) and magnetic polystyrene (MPS) materials have been used extensively in wastewater treatment. In this research, a 55-day anaerobic/oxic process was carried out to evaluate the effects of PS and MPS on microorganisms under aerobic and anaerobic conditions. Scanning electron microscopy results revealed differences in the entanglement state of the sludge with the biocarrier due to differences in surface morphology. High-throughput sequencing analysis showed that the microbial communities differed considerably in the presence of PS and MPS addition under both aerobic and anaerobic conditions. The highest abundance and diversity were observed in the PS reactor, with 929 observed species and a PD_whole_tree index of 91.58 under anaerobic conditions. MPS promoted the enrichment of bacteria related to nitrogen recycling such as Nitrospirota which increased from 1.13% in the seeding sludge to 3.48% and 10.07% in the aerobic reactors with PS and MPS, respectively. Moreover, advanced analysis showed that PS inhibited many microbial functions (e.g., protein export, nitrogen metabolism), and MPS alleviated this inhibition. This study provides significant insights into the microbial effects of PS and MPS and may shed light on biocarrier selection in future studies.

Adsorptive removal of Safranine T dye from aqueous solutions using sodium alginate-Festuca arundinacea seeds bio-composite microbeads

In this study, composite microbeads were prepared using Festuca arundinacea seeds and sodium alginate biopolymer at different ratios and utilized as sorbents for the sorption of Safranine T from wastewater. The sorbents were characterized by FTIR, SEM, XRD, and BET analysis. According to BET analysis, the specific surface area of the adsorbents was calculated to be 10.99 m2/g and the surface was found to be mesoporous. The optimum conditions for adsorption studies including initial pH (2-12), concentration (10-50 mg/L), contact time (0-150 min), and adsorbent mass (0.05 g/50 mL-0.25 g/50 mL) were determined at 25 °C. The raw data obtained from sorption tests were applied to Freundlich, Langmuir-1, Langmuir-2, Langmuir-3, Langmuir-4, Temkin, Toth, and Koble-Corrigan isotherm models. The best results were obtained from the Langmuir-2 and accordingly the qm values were calculated as 454.54, 833.33, and 625.00 mg/g for FA, FA-SA-20, and FA-SA-30 at 25 °C, respectively. Adsorption kinetic data illustrated that the process followed the PSO model. Reusability and desorption studies were performed for composite microbeads. Additionally, the thermodynamic studies were performed at 25, 35 and 45 °C. Considering all these results, it was seen that the FA-SA-20 composite had the highest adsorption capacity and the best desorption efficiency.

Adsorbents obtained from recycled polymeric materials for retention of different pollutants: A review

Polymeric waste is an environmental problem, with an annual world production of approximately 368 million metric tons, and increasing every year. Therefore, different strategies for polymer waste treatment have been developed, and the most common are (1) redesign, (2) reusing and (3) recycling. The latter strategy represents a useful option to generate new materials. This work reviews the emerging trends in the development of adsorbent materials obtained from polymer wastes. Adsorbents are used in filtration systems or in extraction techniques for the removal of contaminants such as heavy metals, dyes, polycyclic aromatic hydrocarbons and other organic compounds from air, biological and water samples. The methods used to obtain different adsorbents are detailed, as well as the interaction mechanisms with the compounds of interest (contaminants). The adsorbents obtained are an alternative to recycle polymeric and they are competitive with other materials applied in the removal and extraction of contaminants.

Preparation of benzenesulfonyl hydrazone modified guar gum and its adsorption properties for dyes and phytotoxicity assays

Herein, a novel environmentally friendly benzenesulfonyl hydrazone modified guar gum (DGH) that carries excellent adsorption performance towards dyes was facilely prepared through oxidation and condensation. The structure, morphology, and physics-chemical of DGH were fully characterized by multiple analysis techniques. The as-prepared adsorbent yielded highly efficient separating performance towards multiple anionic and cation dyes, including CR, MG, and ST with the maximum adsorption capacity of 1065.3839 ± 10.5695, 1256.4467 ± 2.9425, and 1043.8140 ± 0.9789 mg/g at 298.15 K, respectively. The adsorption process well fitted the Langmuir isotherm models and the pseudo-second-order kinetic models. The adsorption thermodynamics revealed that the adsorption of dyes onto DGH was spontaneous and endothermic. The adsorption mechanism indicated that the hydrogen bonding and electrostatic interaction participated in the fast and efficient removal of dyes. Furthermore, the removal efficiency of DGH still remained above 90 % after six adsorption-desorption cycles, and the presence of Na⁺, Ca²⁺, and Mg²⁺ have weakly impacted the removal efficiency of DGH. The phytotoxicity assay was conducted via the germination of mung bean seeds, which confirmed the adsorbent can effectivity decreased the toxicity of dyes. Overall, the modified gum-based multifunctional material has good promising applications for wastewater treatment.

Upcycling waste expanded polystyrene into UV-excited dual-mode multicolor luminescent electrospun fiber membranes for advanced anti-counterfeiting†

Expanded polystyrene (EPS) is causing severe environmental problems due to its high consumption and non-biodegradability. Upcycling waste EPS into high value-added functional materials is highly advisable in terms of sustainability and environmental concerns. Meanwhile, it is imperative to develop new anti-counterfeiting materials with high security against increasingly high-tech counterfeiting. Developing UV-excited dual-mode luminescent advanced anti-counterfeiting materials that can be excited by commonly used commercial UV light sources (such as 254 nm and 365 nm wavelengths) remains a challenge. Herein, UV-excited dual-mode multicolor luminescent electrospun fiber membranes were fabricated from waste EPS by co-doping with a Eu³⁺ complex and a Tb³⁺ complex via electrospinning. The SEM results prove that the lanthanide complexes are uniformly dispersed in the PS matrix. The luminescence analysis results suggest that all the as-prepared fiber membranes with the different mass ratios of the two complexes can exhibit the characteristic emission of Eu³⁺ ions and Tb³⁺ ions under UV light excitation. The corresponding fiber membrane samples can exhibit intense visible luminescence with different colors under UV lights. Moreover, each membrane sample can display different color luminescence irradiated with UV light at 254 nm and 365 nm, respectively, e.g. show excellent UV-excited dual-mode luminescent properties. This is owing to the different UV absorption properties of the two lanthanide complexes doped in the fiber membrane. Finally, the fiber membranes with different color luminescence from green light to red light were achieved by tuning the mass ratio of the two complexes in the PS matrix and changing UV irradiation wavelengths. The as-prepared fiber membranes with tunable multicolor luminescence are very promising for high-level anti-counterfeiting applications. This work is very meaningful not only to upcycle waste EPS to high value-added functional products but also to develop advanced anti-counterfeiting materials.

A simple and effective method to upcycle waste EPS to UV-excited dual-mode multicolor luminescent membranes for advanced anti-counterfeiting was developed.

Multi-step preparation of Fe and Si modified biochar derived from waterworks sludge towards methylene blue adsorption

A magnetic nitrogen-doped sludge-based biochar (NAlSB-Fe-Si) was prepared based on waterworks sludge for raw material and dicyandiamide for nitrogen source to adsorb methylene blue (MB) from water. And the magnetic particles loaded on the adsorbent were obtained through functionalizing iron and silicon ions which were extracted from the biochar by acid and alkali impregnation. Physicochemical properties of sludge-based biochar (SB) were analyzed by SEM, BET, FTIR, XRD, XPS and VSM. Compared with the original biochar, NAlSB-Fe-Si had richer pore structure and higher pore volume, and the SiO₂ and Fe₃O₄ loading made the specific surface area increased by 200%. Possible adsorption mechanism was proposed by exploring the initial pH, MB concentration and reaction time. Results revealed that alkaline environment was more conducive to the rapid removal of cationic dyes such as MB. Pseudo-second-order kinetic model and intra-particle diffusion model could describe the adsorption behavior of MB on NAlSB-Fe-Si. The fitting results of Langmuir model showed that adsorption temperature is positively correlated with adsorption capacity, and the maximum adsorption capacity of MB on nitrogen-doped sludge-based biochar (NSB) and NAlSB-Fe-Si at 25 °C was 26.47 and 300.36 mg/g, respectively. Finally, the MB removal rate of NAlSB-Fe-Si could still reach 70% after four cycles, indicating that the composite was an efficient cationic dye adsorbent, and its preparation could be regarded as a way of resource utilization of waterworks sludge.

Magnetic cross-linked chitosan for efficient removing anionic and cationic dyes from aqueous solution

Herein, a novel magnetic cross-linked chitosan CS-BA@Fe₃O₄ was rationally synthesized by cross-linked with epichlorohydrin and coated with Fe₃O₄ to the acylated chitosan, which was prepared by the reaction of chitosan with benzenetricarboxylic anhydride. The as-obtained absorbent was characterized by FTIR, XRD, VSM, TGA, TEM, BET, SEM and EDS. The results showed that the maximum adsorption capacities of CR and CV were 471.46 ± 16.97 mg/g and 515.91 ± 25.12 mg/g at 318.15 K, respectively. The main adsorption mechanisms were H-bonding and electrostatic interaction. The kinetic data were in good agreement with the pseudo-second-order model and closed to adsorption equilibrium at 30 min. Thermodynamic studies showed that the adsorption on CS-BA@Fe₃O₄ were spontaneous and endothermic. More importantly, the adsorbent exhibited excellent regeneration properties after 6 cycles and remarkable stability under harsh environments including strong acid, strong alkali, multi-salt and mixed dyes conditions. Therefore, abundant efforts revealed a broad application prospect of CS-BA@Fe₃O₄ in water remediation.