Magnetite nanoparticles modified β-cyclodextrin PolymerCoupled with KMnO4 oxidation for adsorption and degradation of acetaminophen

Peracetic acid pretreatment improves biogas production from anaerobic digestion of sewage sludge by promoting organic matter release, conversion and affecting microbial community

Peracetic acid (PAA) pretreatment is considered as a novel and effective chemical pretreatment method for sludge. However, there is little information available on potential mechanisms of how PAA pretreatment affects sludge anaerobic digestion (AD). To fill the knowledge gap, this study investigated the effects and potential mechanisms of PAA pretreatment on sludge AD systems from physicochemical and microbiological perspectives. Batch experiments resulted that biogas production was enhanced by PAA pretreatment and the highest cumulative biogas yield (297.94 mL/g VS (volatile solid)) was obtained with 2 mM/g VS of PAA pretreatment. Kinetic model analysis illustrated that the PAA pretreatment improved the biogas potential (Pt) of sludge AD, but prolonged the lag phase (λ) of AD. Mechanistic studies revealed that reactive oxygen species (ROS) (HO•, O2-•, 1O2 and CH3C(O)OO•) were the major intermediate products of PAA decomposition. These ROS effectively promoted the decomposition and solubilization of sludge, and provided more biodegradable organic matter for the following AD reactions. 16S rRNA amplicon sequencing showed that some functional microorganisms associated with hydrolysis, acidogenesis, acetogenesis as well as methanogenesis, such as Hydrogenispora, Romboutsia, Longivirga, Methanosarcina and Methanosaet, were significantly enriched in reactors pretreated with PAA. Redundancy analysis and variation partitioning analysis indicated that functional microorganisms were significantly correlated with intermediate metabolites (soluble carbohydrate, soluble protein, soluble chemical oxygen demand and volatile fatty acids) and cumulative biogas production. This study provides a fresh understanding of the effects and mechanisms of PAA pretreatment on sludge AD, updates the insights into the response of functional microorganisms to PAA pretreatment, and the findings obtained might provide a fundamental basis for chemical pretreatment of sludge AD using oxidants.

Mechanism analysis of efficient degradation of carbamazepine by chalcopyrite-activated persulfate

In this study, natural chalcopyrite (NCP) was used to activate peroxymonosulfate (PMS) to degrade carbamazepine (CBZ) oxidatively. Before and after the NCP reaction, the physical and chemical properties were characterized by SEM-EDS, XRD, XPS, XRF, and VSM. The effects of the amount of NCP and PMS, the initial pH value, and the reaction temperature on the catalytic performance of NCP were systematically studied. The research results show that the degradation efficiency of the NCP/PMS system for CBZ can reach 82.34% under the optimal reaction conditions, and the degradation process follows a pseudo-second-order kinetic model. The results of the radical quenching experiment and EPR analysis show that the active species in the system are OH·, SO₄^-·, and ¹O², of which SO₄^-· is the main active species. In addition, this study shows that the NCP/PMS system can degrade CBZ with high efficiency of 90.73% only with the assistance of 0.15 g/L Fe⁰. This study determined the optimal reaction conditions for natural chalcopyrite to activate PMS to degrade CBZ and clarified the activation mechanism, which broadened the application of natural ores in the field of water treatment.

Construction of a magnetic solid-phase extraction method for the analysis of azole pesticides residue in medicinal plants

In this work, a sensitive and cost-effective method for the quantitative analysis of azole pesticides residues in six medicinal plants was established based on magnetic cyclodextrin crosslinked with tetrafluoroterephthalonitrile (Fe₃O₄@TFN-CDPs) coupled with high-performance liquid chromatography (HPLC). Through characterization analysis, the outer shell of Fe₃O₄@TFN-CDPs has observed coating with a network of the polymer and forming a core-shell structure. Under the optimum conditions, the limits of detection (LODs) and limits of qualification (LOQs) of target pesticides were ranged from 0.011 to 0.106 µg Kg^-1 and from 0.036 to 0.354 µg Kg^-1, respectively. Finally, the achieved recoveries of pesticides in six medicinal samples fluctuated from 60.1% to 102.3%. Altogether, this method based on Fe₃O₄@TFN-CDPs composites provided a new idea for the analysis of trace pesticides in complicated matrices.

Synthesis of a highly recoverable 3D MnO2/rGO hybrid aerogel for efficient adsorptive separation of pharmaceutical residue

Water contamination by non-steroidal anti-inflammatory drugs, such as acetaminophen, is an emerging ecological concern. In this study, a new three-dimensional manganese dioxide-engrafted reduced graphene oxide (3D MnO₂/rGO) hybrid aerogel was developed for acetaminophen sequestration. The synthesis involved firstly the self-assembly of GO aerogel, followed by thermal reduction and in-situ MnO₂ growth by redox-reaction. The aerogel demonstrated interlinked planes with smooth surfaces deposited with MnO₂ nanospheres and pores of 138.4 - 235.3 µm width. The influences of adsorbent dosage, initial pH, acetaminophen concentration, temperature and contact time were investigated. It was determined that the adsorption of acetaminophen occurred on uniform sorption sites in the aerogel, as suggested by the best fit of data to the Langmuir isotherm, yielding a maximum adsorption capacity of 252.87 mg/g. This highest adsorption performance of the 3D MnO₂/rGO aerogel was attained at a dosage of 0.6 g/L, initial pH of 6.2 and temperature of 40°C. The process kinetics were in-line with the pseudo-first-order and pseudo-second-order kinetics at 10 and 20 - 500 mg/L concentrations, respectively. Thermodynamic assay showed the spontaneity and endothermicity features of the 3D MnO₂/rGO-acetaminophen system. The acetaminophen adsorption mechanisms were mainly hydrogen bonding and pore entrapment. Moreover, the as-synthesised aerogel was effectively regenerated using acetone and re-utilised in four adsorption-desorption cycles. Overall, the results highly recommend the implementation of the 3D MnO₂/rGO hybrid aerogel for purification of wastewater polluted by acetaminophen residue.

Sustainable Mitigation of Paracetamol with a Novel Dual-Functionalized Pullulan/Kaolin Hydrogel Nanocomposite from Simulated Wastewater

In the present investigation, a novel, green, and economical dual-functionalized pullulan/kaolin hydrogel nanocomposite (f-PKHN) was fabricated and subsequently applied for the liquid-phase decontamination of paracetamol (PCT), a pharmaceutical pollutant. Pullulan and kaolin were functionalized with l-asparagine and gallic acid, respectively. The physicochemical facets of the functionalized pullulan/kaolin hydrogel nanocomposite and its interactive behavior with PCT were elucidated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDX), and elemental mapping. The process parameters along with the isotherm, kinetics, and thermodynamics were methodically appraised via a batch technique to unveil the adsorption performance of the as-fabricated hydrogel nanocomposite. The adsorption isotherm and kinetics of PCT uptake by f-PKHN conform well to Freundlich and pseudo-second-order models, respectively. Relying on hydrogen bonding, n-π, and van der Waals interactions, the maximum adsorption capacity was 332.54 mg g^-1, higher than for most of the previous adsorbents reported in the literature for PCT removal. Thermodynamic calculations corroborated endothermic, spontaneous, and feasible adsorption phenomena. The maintenance of a high uptake percentage (69.11%) in the fifth consecutive adsorption-desorption cycle implied the significant reusable potential of f-PKHN. Swelling studies exhibited 90% swelling within 200 min, indicating the successful fabrication of a cross-linked hydrogel network. The real water (distilled water, tap water, and river water) samples spiked with PCT specified a significant uptake of PCT (>85%), and the minor influence of ionic strength on the adsorptive potential of f-PKHN validated its potentiality for the decontamination of real effluents. In conclusion, f-PKHN with substantial adsorption capacity, green characteristics, and excellent reusability can be reckoned with as a promising adsorbent for the de-escalation of PCT from aquatic sources as well as at the industrial level.

Enhanced degradation of sulfamethoxazole by a modified nano zero-valent iron with a β-cyclodextrin polymer: Mechanism and toxicity evaluation

Rising concern about emerging and already persisting pollutants in water has urged the scientific community to develop novel remedial techniques. A new group of remediation methods is based on the modification of nanoscale zero-valent iron particles (nZVI), which are well known for treating volatile organic compounds and heavy metals. The properties of nZVI may be further enhanced by modifying their structure or surface using "green" polymers. Herein, nZVI was modified by a β-cyclodextrin polymer (β-CDP), which is considered an environmentally safe and inexpensive adsorbent of contaminants. This composite was used for the first time for the degradation of sulfamethoxazole (SMX). Coating by β-CDP not only enhanced the degradation of SMX (>95%, under 10 min) by the nanoparticles in a wide pH range (3-9) and enabled their efficient reusability (for three cycles) but also made the coated nZVI less toxic to the model bioindicator microalga Raphidocelis subcapitata. Moreover, degradation products of SMX were found to be less toxic to Escherichia coli bacteria and R. subcapitata microalga, contrary to the SMX antibiotic itself, indicating a simple and eco-friendly cleaning process. This research aims to further stimulate and develop novel remedial techniques based on nZVI, and provides a potential application in the degradation of antibiotics in a wide pH range. Moreover, the wealth of available cyclodextrin materials used for surface modification may open a way to discover more efficient and attractive composites for environmental applications.

Environmentally friendly fabrication of new β-Cyclodextrin/ZrO2 nanocomposite for simultaneous removal of Pb(II) and BPA from water

Heavy metals and endocrine disrupters often co-exist in wastewater, while their possible competition behaviours make uptake removal more challenging. Therefore, β-Cyclodextrin based nanocomposite adsorbent was successfully fabricated (β-Cyclodextrin/ZrO₂) for the simultaneous uptake of Pb(II) and Bisphenol A from wastewater. FTIR, XRD, and XPS confirmed the successful fabrication of the β-Cyclodextrin/ZrO₂ nanocomposite. In this setting, oxygen-containing groups are primarily responsible for the Pb(II) binding, while the β-Cyclodextrin cavities adsorb Bisphenol A through host-guest interaction, enabling the simultaneous removal of Pb(II) and Bisphenol A. In the mono contaminant system, the nanocomposite displayed prominent removal ability toward Pb(II) and Bisphenol A with adsorption characteristics of pseudo-second-order, Langmuir, and Freundlich isotherm model. The maximum adsorption capacities were identified for Pb(II) and Bisphenol A to be 274.4 mg/g and 174.9 mg/g at 298 K, respectively. Most importantly, the β-Cyclodextrin/ZrO₂ could efficiently attain simultaneous removal of Pb(II) and Bisphenol A by avoiding their competitive behaviours was due to the different adsorption mechanisms (electrostatic interaction and host-guest interaction). Moreover, the adsorbed Pb(II) and Bisphenol A could be successfully recovered with a slight decline in nanocomposite removal performance even after 4 cycles in the binary-component system. All these findings provide insights into the fabrication of highly effective adsorbent with separated adsorption sites to treat wastewater bearing heavy metal and endocrine disrupters.

Comparison of the Efficiency of Ultraviolet/Zinc Oxide (UV/ZnO) and Ozone/Zinc Oxide (O3/ZnO) Techniques as Advanced Oxidation Processes in the Removal of Trimethoprim from Aqueous Solutions

Nowadays, advanced oxidation processes, particularly photocatalyst process and catalytic ozonation by ZnO nanoparticles, are the most efficient method of eliminating pharmaceuticals. The purpose of this study was to compare the efficiency of ultraviolet/zinc oxide (UV/ZnO) and ozone/zinc oxide (O3/ZnO) techniques as advanced oxidation processes in the removal of trimethoprim (TMP) from aqueous solutions. The process consisted of 0.6 g/L of ozone (O3), pH = 7.5 ± 0.5, TMP with a concentration of 0.5–5 mg/L, ZnO with a dose of 50–500 mg/L, 5–30 min reaction time, and 30–180 min contact time with UV radiation (6 W, 256 nm) in a continuous reactor. The high removal efficiency was achieved after 25 minutes when ZnO is used in 1 mg/L TMP under an operational condition at pH 7.5. When the concentration of the pollutant increased from 0.5 to 1, the average removal efficiency increased from 78% to 94%, and then, it remained almost constant. An increase in the reaction time from 5 to 25 minutes will cause the average elimination to increase from 84% to 94%. The results showed that the efficiency of O3/ZnO process in the removal of TMP was 94%, while the removal efficiency of UV/ZnO process was 91%. The findings exhibited that the kinetic study followed the second-order kinetics, both processes. With regard to the results, the photocatalyst process and catalytic ozonation by ZnO nanoparticles can make acceptable levels for an efficient posttreatment. Finally, this combined system is proven to be a technically effective method for treating antibiotic contaminants.

Cyclodextrin-based adsorbents for the removal of pollutants from wastewater: a review

Water is a vital substance that constitutes biological structures and sustains life. However, water pollution is currently among the major environmental challenges and has attracted increasing study attention. How to handle contaminated water now mainly focuses on removing or reducing the pollutants from the wastewater. Cyclodextrin derivatives, possessing external hydrophilic and internal hydrophobic properties, have been recognized as new-generation adsorbents to exert positive effects on water pollution treatment. This article outlines recent contributions of cyclodextrin-based adsorbents on wastewater treatment, highlighting different adsorption mechanisms of cyclodextrin-based adsorbents under different influencing factors. The crosslinked and immobilized cyclodextrin-based adsorbents all displayed outstanding adsorption capacities. Particularly, according to specific pollutants including metal ions, organic chemicals, pesticides, and drugs in wastewater, this article has classified and organized various cyclodextrin-based adsorbents into tables, which could pave an intuitive shortcut for designing and developing efficient cyclodextrin-based adsorbents for targeted wastewater pollutants. Besides, this article specially discusses cost-effectiveness and regeneration performance of current cyclodextrin-based adsorbents. Finally, the challenges and future directions of cyclodextrin-based adsorbents are prospected in this article, which may shed substantial light on practical industrial applications of cyclodextrin-based adsorbents.

Simultaneously enhanced removal and stepwise recovery of atrazine and Pb(II) from water using β-cyclodextrin functionalized cellulose: Characterization, adsorptive performance and mechanism exploration

Heavy metals and pesticides often coexist in contaminated water, while their potential competition behaviors make the adsorptive removal more challenging. Thus, decorating an adsorbent with independent functional sites could be a promising alternative to radically prevent the competitive process for improving the adsorption performance. Herein, β-cyclodextrin functionalized rice husk-based cellulose (β-CD@RH-C) was designed and applied for synchronous removal of atrazine and Pb(II). The characterization results supported the successful grafting of β-cyclodextrin onto the cellulose. The β-CD@RH-C presented a pH-dependent adsorption performance for Pb(II) with a theoretical monolayer adsorption capacity of 283.00 mg/g, while was mostly unrelated to pH for atrazine adsorption with a heterogeneous uptake of 162.21 mg/g in the mono-component system. Most importantly, the β-CD@RH-C could efficiently achieve simultaneous removal of atrazine and Pb(II) via avoiding their competitive behaviors, which was due to the different adsorption mechanisms for atrazine (i.e. host-guest interaction) and Pb(II) (i.e. complexation and electrostatic interaction). Moreover, the adsorbed atrazine and Pb(II) could be sequentially desorbed with slight decrease in the adsorption performance of β-CD@RH-C even after four cycles in the atrazine-Pb(II) multi-component system. All these results suggested β-CD@RH-C to be a tailored adsorbent with high-performance elimination of co-existing heavy metals and organic pollutants in water.

Removal of 17β-Estradiol (E2) from Aqueous Solutions Using Potassium Permanganate Combined with Ultraviolet (KMnO4/UV)

17β-Estradiol (E2) has a significant health risk to humans, even at the ng/L level, and is discharged to the aqueous environment through wastewater. Advanced oxidation processes were proposed as an efficient process for the removal of E2. In this study, a combination of ultraviolet-C (UV-C) and KMnO4 was applied for the removal of E2. Results have shown that the removal efficiency of E2 in pH 4 (acidic condition) was 93.80 ± 0.42%. But, removal efficiency in neutral (7) and alkaline (10) conditions was 78.3 ± 2.12% and 84 ± 0.71%, respectively. The effect of Fe+2, Ca+2, Mg+2, Mn+2, and Fe+3 ions (1 mg/L) was investigated in optimized pH (4). Mn+2, Fe+2, and Ca+2 ions enhanced the removal efficiency to 94.8 ± 0.84%, 95.55 ± 0.07%, and 94.7 ± 0.14%, respectively $\left(p>0.05\right)$ , while Mg+2 and Fe+3 ions decreased the removal efficiency significantly to 76.15 ± 1% and 83.91 ± 0.3% $\left(p<0.05\right)$ . The efficiency of E2 removal in the presence of 5 mg/L of PAC reduced significantly to 85 ± 4.24% $\left(p<0.05\right)$ . Also, humic substances like humic acid, fulvic acid, and a combination of them could enhance the efficiency to 99.87 ± 0.01%, 99.9 ± 0.06%, and 99.93 ± 0.014%, respectively $\left(p>0.05\right)$ . The result indicates that the rate of oxidation of E2 is related to the second exponent of the initial concentration of E2 for optimum pH and the presence of all ions. But, in the presence of humic substances, the first-order kinetic reaction was best applicable in describing oxidation of E2. Removal of chemical oxygen demand for E2 after 120 minutes’ of contact time at optimum pH (86 ± 4.2%) demonstrated mineralization of these compounds at acceptable levels. Results presented that the UV-C/KMnO4 process is efficient for the removal of hormones from the aqueous solution.

The classification and application of cyclodextrin polymers: a review

After introducing the concept of cyclodextrin polymers, their classification and applications have been summarized.