Conversion of post consumer waste polystyrene into a high value adsorbent and its sorptive properties for Congo Red removal from aqueous solution

A novel mycelial pellet applied to remove polycyclic aromatic hydrocarbons: High adsorption performance & its mechanisms

Mycelial pellets formed by Penicillium thomii ZJJ were applied as efficient biosorbents for the removal of polycyclic aromatic hydrocarbons (PAHs), which are a type of ubiquitous harmful hydrophobic pollutants. The live mycelial pellets were able to remove 93.48 % of pyrene at a concentration of 100 mg/L within 48 h, demonstrating a maximum adsorption capacity of 285.63 mg/g. Meanwhile, the heat-killed one also achieved a removal rate of 65.01 %. Among the six typical PAHs (pyrene, phenanthrene, fluorene, anthracene, fluoranthene, benzo[a]pyrene), the mycelial pellets preferentially adsorbed the high molecular weight PAHs, which also have higher toxicity, resulting in higher removal efficiency. The experimental results showed that the biosorption of mycelial pellets was mainly a spontaneous physical adsorption process that occurred as a monolayer on a homogeneous surface, with mass transfer being the key rate-limiting step. The main adsorption sites on the surface of mycelia were carboxyl and N-containing groups. Extracellular polymeric substances (EPS) produced by mycelial pellets could enhance adsorption, and its coupling with dead mycelia could achieve basically the same removal effect to that of living one. It can be concluded that biosorption by mycelial pellets occurred due to the influence of electrostatic and hydrophobic interactions, consisting of five steps. Furthermore, the potential applicability of mycelial pellets has been investigated considering diverse factors. The mycelia showed high environmental tolerance, which could effectively remove pyrene across a wide range of pH and salt concentration. And pellets diameters and humic acid concentration had a significant effect on microbial adsorption effect. Based on a cost-effectiveness analysis, mycelium pellets were found to be a low-cost adsorbent. The research outcomes facilitate a thorough comprehension of the adsorption process of pyrene by mycelial pellets and their relevant applications, proposing a cost-effective method without potential environmental issues (heat-killed mycelial pellets plus EPS) to removal PAHs.

Recoverable cellulose composite adsorbents for anionic/cationic dyes removal

GO/HEC/PGDE/Fe₃O₄ materials were successfully fabricated using environmentally-friendly hydroxyethyl cellulose (HEC), poly(ethylene glycol) diglycidyl ether (PGDE), graphene oxide (GO) and magnetic Fe₃O₄. Systematic investigations were completed to explore the influences of GO content in GO/HEC/PGDE/Fe₃O₄ and adsorption conditions on the adsorptions of cationic dyes (methylene blue (MB), crystal violet (CV)) and anionic dye acid blue 25 (AB-25). The increase of GO content can remarkably improve the adsorption capacity of GO/HEC/PGDE/Fe₃O₄ for the dyes. The three kinetic, four isothermic and three thermodynamic models were investigated to reveal the adsorption behaviors of the dyes. The formation of HEC/PGDE/Fe₃O₄ and adsorption mechanisms of the dyes by GO/HEC/PGDE/Fe₃O₄ were suggested. The GO/HEC/PGDE/Fe₃O₄ endowed with easy-fabrication, eco-friendly feature, efficient adsorption capacity of anionic/cationic dyes, convenient separation and reusability has potential applications in wastewater purification industry.

Waste expanded polystyrene modified with H2SO4/biodegradable chelating agent for reuse: As a highly efficient adsorbent to remove fluoroquinolone antibiotic from water

Untreated wastewater containing fluoroquinolone antibiotics poses serious hazards to aquatic species and human health; therefore, treatment of waste expanded polystyrene (EPS) is a crucial environmental matter. In this study, waste EPS was modified with a H₂SO₄/biodegradable chelating agent, [S,S]-ethylenediamine-N,N'-disuccinic acid (EDDS), and used for highly efficient adsorption of the fluoroquinolone antibiotic ciprofloxacin. When ciprofloxacin of 25 mg/L was used, the H₂SO₄-modified EPS (EPS_H2SO4) adsorbed 60.5% of the ciprofloxacin. During sulfonation, adding a low dose of EDDS markedly improved the adsorption ability of EPS_H2SO4+EDDS. The optimal modification conditions were 95% H₂SO₄, 0.002 M EDDS, 80 °C, and 40 min. The increased adsorbent doses enhanced the adsorption. Approximately 0.2 g/L of EPS_H2SO4+EDDS could effectively adsorb 97.8% of the ciprofloxacin (554.3 mg/g) within 30 min. Solution pH₀ greatly influenced the adsorption, and the most suitable pH₀ was 6. The Langmuir isotherm accurately described the adsorption behaviors of both EPS_H2SO4 and EPS_H2SO4+EDDS (R² = 0.997-0.998). The adsorption ability of EPS_H2SO4+EDDS (q_max = 1250 mg/g) was 32 times higher than that of EPS_H2SO4 (q_max = 38.6 mg/g). A total of 1 M HCl effectively regenerated the exhausted adsorbent. The optimal solid/liquid ratio and time were 0.08 g/20 mL and 60 min, respectively. The regenerated EPS_H2SO4+EDDS maintained a high adsorption ability (87.2%) after 10 regeneration cycles. The results thus indicate that the EPS_H2SO4+EDDS adsorption-regeneration process is a potential approach to remove ciprofloxacin from water.

Self-immobilized biochar fungal pellet combined with bacterial strain H29 enhanced the removal performance of cadmium and nitrate

A newly isolated strain Phoma sp. ZJ6, which could form fungal pellet (FP) by self-immobilization, was identified. A novel longan seed biochar embedded in FP (BFP) combined with strain H29 (BFP-H29) effectively improved the Cd(II) removal efficiency and simultaneously removed nitrate. The adsorption process of BFP was well fitted with the pseudo-second-order kinetics model and Langmuir isotherm model, which demonstrated that the adsorption process was favorable and mainly dominated by chemisorption. Compared with single FP, biochar, and strain H29, BFP-H29 significantly enhanced the Cd(II) removal and the removal ratio reached 90.47%. Meanwhile, the simultaneous removal efficiency of the BFP-H29 for nitrate could reach 93.80%. Characterization analysis demonstrated that the primary removal mechanisms of BFP-H29 were precipitation and surface complexation. BFP-H29 had excellent performance in simultaneous removal of Cd(II) and nitrate, indicating its potential as a promising composite in the removal of cadmium and nitrate in wastewater.

Thiol-Yne Click Postsynthesis of a Sulfonate Group-Enriched Magnetic Microporous Organic Network for Efficient Extraction of Benzimidazole Fungicides

The lack of functional groups or binding sites largely hindered the broad application of microporous organic networks (MONs). Herein, we report the fabrication of the sulfonate group-enriched magnetic MON composite (MMON-SO₃H@SO₃Na) via the combination of the sulfonic acid group containing the monomer and thiol-yne click postmodification for efficient magnetic solid-phase extraction (MSPE) of benzimidazole fungicides (BZDs) from complex sample matrices. The well-defined core-shell-structured MMON-SO₃H@SO₃Na was obtained and served as an advanced adsorbent for MSPE for concentrating and monitoring trace BZDs. The MMON-SO₃H@SO₃Na with numerous sulfonate groups provides plenty of ion-exchange, hydrogen-bonding, and π-π sites, leading to the favorable affinity to BZDs via multiple interaction mechanisms. The MMON-SO₃H@SO₃Na-based MSPE-high-performance liquid chromatography method afforded a wide linear range, low limits of detection, large enrichment factors, good precisions, and reusability for BZDs. Trace BZDs in complex vegetables and fruit samples were successfully detected by the established method. The MMON-SO₃H@SO₃Na also exhibited good selectivity toward multiple types of polar contaminants containing hydrogen-bonding sites and aromatic structures. This work provided a new postsynthesis strategy for constructing novel and multifunctioned magnetic MONs for preconcentration of trace analytes in a complex matrix.

Fabrication of magnetic polydopamine@naphthyl microporous organic network nanosphere for efficient extraction of hydroxylated polycyclic aromatic hydrocarbons and p-nitrophenol from wastewater samples

Herein, we report the fabrication of a novel, well-defined core-double-shell-structured magnetic Fe₃O₄@polydopamine@naphthyl microporous organic network (MON), Fe₃O₄@PDA@NMON, for the efficient magnetic extraction of hydroxylated polycyclic aromatic hydrocarbons (OH-PAHs) and p-nitrophenol (p-Npn) from wastewater samples. The hierarchical nanospheres were designed and constructed with the Fe₃O₄ nanoparticle core, the inner shell of a polydopamine (PDA) layer, and the outer shell of a porous naphthyl MON (NMON) coating, allowing efficient and synergistic extraction of OH-PAHs and p-Npn via hydrophobic, hydrogen bonding, and π-π interactions. The Fe₃O₄@PDA@NMON nanospheres were well characterized and employed as an efficient sorbent for magnetic solid-phase extraction (MSPE) coupled with high performance liquid chromatography (HPLC) for analyzing of OH-PAHs and p-Npn. Under optimal conditions, the Fe₃O₄@PDA@NMON-based-MSPE-HPLC-UV method afforded wide linear range (0.18-500 μg L^-1), low limits of detection (0.070 μg L^-1 for p-Npn, 0.090 μg L^-1 for 2-OH-Nap, 0.090 μg L^-1 for 9-OH-Fluo and 0.055 μg L^-1 for 9-OH-Phe, respectively), large enrichment factors (92.6-98.4), good precisions (intra-day and inter-day relative standard deviations (RSDs); <6.4%, n=6) and less consumption of the adsorbent. Furthermore, trace OH-PAHs and p-Npn with concentrations of 0.29-0.80 μg L^-1 were successfully detected in various wastewater samples. Fe₃O₄@PDA@NMON also functioned as a good adsorbent to enrich a wide scope of trace contaminants containing hydrogen bonding sites and aromatic structures, highlighting the potential of functional MONs in sample pretreatment.

Amidation modified waste polystyrene foam as an efficient recyclable adsorbent for organic dyes removal

Modifying environmentally harmful waste polystyrene foam as an efficient recyclable adsorbent for organic dyes is important. Amidation modified polystyrene (PS-SD) was prepared by the Friedel-Crafts reaction and N,N'-dicyclohexylcarbodiimide (DCC) dehydration condensation reaction of waste polystyrene foam. PS-SD had highly efficient removal performance for organic dyes in large volume water sample solutions, and equilibrium was achieved in 0.5 h. The maximum adsorption capacities for Methylene blue (MB) and Congo red (CR) were 881.62 and 1,880.91 mg/g, respectively, at room temperature according to the Langmuir adsorption isotherm (R² > 0.99). The kinetic data of the two dyes followed pseudo-second-order kinetics. The removal percentage remained high (>85%) after eight filtration-regeneration cycles. Experimental results showed that PS-SD was an excellent adsorbent for water treatment with high recyclability and long life.

Biosorption of Congo Red from Aqueous Solutions Based on Self-Immobilized Mycelial Pellets: Kinetics, Isotherms, and Thermodynamic Studies

In the current study, Aspergillus fumigatus and Pseudomonas putida were co-cultured to obtain self-immobilized mycelial pellets to evaluate the decolorization efficiency of Congo red (CR). The obtained co-culture exhibited the highest decolorization efficiency of 99.22% compared to monoculture of A. fumigatus (89.20%) and P. putida (55.04%). The morphology and surface properties of the mycelial pellets were characterized by SEM, FTIR, BET, and XPS. The adsorption kinetics and isotherms were well described by pseudo-second-order and Langmuir models. The findings revealed that the removal efficiency of the mycelial pellet for CR was significantly influenced by physicochemical parameters. Thermodynamic result showed that the biosorption process was endothermic. The maximum adsorption capacity can be obtained from the Langmuir model, which is 316.46 mg/g, it suggests that mycelial pellet was an efficient biosorbent to remove CR from aqueous solution. This study indicates that the mycelial pellet can develop a sustainable approach to eliminate CR from the wastewater.

The effect of solvent parameters on properties of iron-based silica binary aerogels as adsorbents

The magnetic Fe₃O₄-SiO₂ binary aerogel and nonmagnetic α-Fe₂O₃-SiO₂ binary aerogels are obtained by adjusting the solvent type during the solvothermal reaction and varying the Fe/Si proportion in the sol-gel process. The microstructure, surface charge and the formation mechanism of iron-based silica binary aerogels are analyzed by SEM, zeta potential and BET. The influence of the Fe/Si proportion on the surface group and morphology of binary aerogels is also investigated by FTIR and TEM analysis. The adsorption behavior of the iron-based silica binary aerogels on the Congo Red (CR) dye is also discussed by adsorption kinetics model and adsorption isotherm model. In addition, the effects of pH and initial concentration of the solutions, adsorption time and the maximum adsorption capacities for CR of iron-based silica binary aerogels adsorbents are also discussed, respectively. Moreover, the maximum adsorption capacity of as-prepared magnetic Fe₃O₄-SiO₂ binary aerogels for dyes achieved 489.13 mg g^-1, the maximum adsorption capacity of nonmagnetic α-Fe₂O₃-SiO₂ reached 454.55 mg g^-1, respectively. Thus, the iron-based silica binary aerogels provides valuable clues for the study of other aerogel materials as adsorbents.

Abatement of humic acid from aqueous solution using a carbonaceous conjugated microporous polymer derived from waste polystyrene

Humic acid (HA) is a major constituent of natural organic matter (NOM) found in water systems. Although NOM generally does not have any known harmful effects to humans, it imparts repulsive organoleptic properties to water, reacts with disinfectants to produce toxic products, and interferes with the efficiency of water treatment processes. The removal of NOM and related compounds from water is therefore important to render water potable and suitable for other applications. In this work, a hitherto unreported carbonaceous conjugated microporous polymer (CCMP) prepared through the organic-polymeric-precursor-controlled carbonization of hypercrosslinked post-consumer waste polystyrene (WPS) was evaluated for its capacity to remove HA from synthetic wastewater. This advanced material retained the morphology of the precursor material, while its porosity and chemical integrity were significantly improved. The approach is an environmentally friendly way of handling WPS while at the same time remediating NOM-contaminated water. Overall, with a maximum adsorption capacity of 340 mg/g in batch experiments, and a maximum initial removal rate of 95.7% in column experiments, the results showed that CCMP can be used for the remediation of HA-contaminated water at high pH.

A Valuable Biochar from Poplar Catkins with High Adsorption Capacity for Both Organic Pollutants and Inorganic Heavy Metal Ions

In this paper, biochar derived from poplar catkins was used as an economical and renewable adsorbent for adsorption organic and inorganic pollutants such as, dyes, organic compounds, and heavy metal ions from wastewater. Mesoporous activated carbonized poplar catkins (ACPCs) were produced from char as a by-product by carbonized poplar catkins (CPCs). With their high surface area, ACPCs exhibited the maximum adsorption capacities of 71.85 and 110.17 mg/g for the removal of inorganic U(VI) and Co(II). Compared other biochars adsorbents, ACPCs can also adsorb organic pollutants with the maximum adsorption capacities of 534, 154, 350, 148 and 384 mg/g for methylene blue (MB), methyl orange (MO), Congo red (CR), chloramphenicol (CAP) and naphthalene. The adsorption of organic pollutants was fitted with pseudo-first order, pseudo-second order, and intra-particle diffusion kinetic models figure out the kinetic parameters and adsorption mechanisms. Langmuir adsorption isotherm was found to be suitable for Co(II) and U(VI) adsorption and thermodynamic studies indicated adsorption processes to be endothermic and spontaneous. The adsorption process includes both outer-sphere surface complexes and hydrogen-bonding interactions. The results showed that biochar derived from poplar catkins was a potential material to remove pollutants in wastewater.

Abnormal adsorption and desorption behavior of pharmaceutical drugs on polystyrene microspheres

We report an abnormal adsorption and desorption behavior where a stronger adsorption interaction between polystyrene particles and pharmaceutical drugs results in preferable desorption behavior.