ZnO nanoparticles loaded different mesh size of porous activated carbon prepared from Pinus eldarica and its effects on simultaneous removal of dyes: Multivariate optimization

Highly efficient and rapid purification of organic dye wastewater using lignin-derived hierarchical porous carbon

Coating manufacturing, textile processing, and plastic industry have led to dramatical release levels of hazardous organic dye pollutants threatening public health and the environment. To solve this problem, porous carbon materials are being developed following with the United Nations initiative on water purification. However, conventional porous carbon materials face many challenges, such as limited removal rates, low adsorption capacity, and high chemicals consumption, hampering their large-scale utilization in dye wastewater treatment. Herein, we demonstrate a high-performance lignin-derived hierarchical porous carbon (LHPC) material directly prepared from renewable lignin through a low-cost activation procedure. The large specific surface area (1824 m²/g) enables the rapid and effective adsorption of organic dyes. Therefore, the LHPC exhibits an ultrahigh adsorption ability (1980.63 mg/g) and removal rate (99.03% in 10 min) for Azure B, superior to that of other adsorbents. Additionally, the LHPC adsorbent, organic dyes, eluting agent, and water all can be recycled and reused in a designed close-looped system. Its high removal ability and rate, strong retrievability, low-cost and scalable production combined with high dyes adsorption universality, positions our LHPC as a promising commercial adsorbent candidate for the purification of harmful organic dye wastewater, especially for heavily polluted area with an insistent demand for clear water.

Preparation of mesoporous silica-based nanocomposites with synergistically antibacterial performance from nano-metal (oxide) and polydopamine

In this work, a novel antibacterial nanocomposite system was developed using mesoporous silica (MSN) as an effective nanocarrier, and the resultant nanocomposites demonstrated remarkable antibacterial performance due to the synergistic effect among nano zinc oxides, silver nanoparticles, and polydopamine (PDA). The successful synthesis of MSN/ZnO@PDA/Ag nanocomposites was confirmed. The physicochemical properties and the morphologies of these nanocomposites were investigated. It was found that the particle size increased along with the evolution of these nanocomposites. Besides, nano zinc oxides were formed in the nanochannels of mesoporous silica with a particle size about 2 nm, and that of silver nanoparticle was less than 50 nm. In addition, the results revealed that the presence of mesoporous silica could effectively prevent the formation of large-size silver nanoparticles and facilitate their well dispersion. Due to the synergistic effect among nano zinc oxides, silver nanoparticles, and polydopamine, these nanocomposites exhibited remarkable antibacterial performance even at a low concentration of 313 ppm, and the antibacterial mechanism was also elucidated. Therefore, this work provides a facile and controllable approach to preparing synergistically antibacterial nanocomposites, and the remarkable antibacterial performance make them suitable for practical applications.

A State-of-the-Art Review on Innovative Geopolymer Composites Designed for Water and Wastewater Treatment

There is nothing more fundamental than clean potable water for living beings next to air. On the other hand, wastewater management is cropping up as a challenging task day-by-day due to lots of new additions of novel pollutants as well as the development of infrastructures and regulations that could not maintain its pace with the burgeoning escalation of populace and urbanizations. Therefore, momentous approaches must be sought-after to reclaim fresh water from wastewaters in order to address this great societal challenge. One of the routes is to clean wastewater through treatment processes using diverse adsorbents. However, most of them are unsustainable and quite costly e.g. activated carbon adsorbents, etc. Quite recently, innovative, sustainable, durable, affordable, user and eco-benevolent Geopolymer composites have been brought into play to serve the purpose as a pretty novel subject matter since they can be manufactured by a simple process of Geopolymerization at low temperature, lower energy with mitigated carbon footprints and marvellously, exhibit outstanding properties of physical and chemical stability, ion-exchange, dielectric characteristics, etc., with a porous structure and of course lucrative too because of the incorporation of wastes with them, which is in harmony with the goal to transit from linear to circular economy, i.e., "one's waste is the treasure for another". For these reasons, nowadays, this ground-breaking inorganic class of amorphous alumina-silicate materials are drawing the attention of the world researchers for designing them as adsorbents for water and wastewater treatment where the chemical nature and structure of the materials have a great impact on their adsorption competence. The aim of the current most recent state-of-the-art and scientometric review is to comprehend and assess thoroughly the advancements in geo-synthesis, properties and applications of geopolymer composites designed for the elimination of hazardous contaminants viz., heavy metal ions, dyes, etc. The adsorption mechanisms and effects of various environmental conditions on adsorption efficiency are also taken into account for review of the importance of Geopolymers as most recent adsorbents to get rid of the death-defying and toxic pollutants from wastewater with a view to obtaining reclaimed potable and sparkling water for reuse offering to trim down the massive crisis of scarcity of water promoting sustainable water and wastewater treatment for greener environments. The appraisal is made on the performance estimation of Geopolymers for water and wastewater treatment along with the three-dimensional printed components are characterized for mechanical, physical and chemical attributes, permeability and Ammonium (NH4+) ion removal competence of Geopolymer composites as alternative adsorbents for sequestration of an assortment of contaminants during wastewater treatment.

Adsorptive removal of eriochrome black T (EBT) dye by using surface active low cost zinc oxide nanoparticles: A comparative overview

The ecological toxicity imparted by non-biodegradable organic dyes has been considered as a major risk to handle in front of mankind. In this view, the low-cost zinc oxide nanoparticles (ZnO-NPs) were facially synthesized by coating the surface with surfactant (CTAB) and ionic liquid (BMTF) molecules for the effective removal of Eriochrome Black T (EBT) from aqueous media. Various advanced characterization techniques have given insight into the morphological features, crystalline structure and physio-chemical properties of as-synthesized ZnO-NPs. The systematic analysis of the adsorption isotherms and kinetics models specifies that the adsorption of EBT follow Freundlich model and pseudo-second-order kinetics. The intraparticle diffusion model displayed a linear relationship (R² = 0.98, 0.97 and 0.94 for BMTF@ZnO, CTAB@ZnO and bare ZnO-NPs), which shows that pore diffusion rate is affected by surface modification and effects the overall EBT adsorption process. Furthermore, after the removal of 87% and 84% of EBT dye by BMTF@ZnO-NPs and CTAB@ZnO-NPs, the fabricated nanoadsorbents of ZnO were successfully regenerated and reused after the treatments up to four times. The adsorption aptitude of ZnO-NPs towards EBT dye was systematically explored in real wastewater samples and interference study of inorganic metallic salts was also performed. The toxicity estimations of the treated dye solutions were made using floral and fungal activities, to ascertain their non-toxic nature before releasing into the environment. These outcomes have supported the immense potential of ZnO-NPs towards the removal of EBT in a cost effective manner.

Robust charge carrier by Fe3O4 in Fe3O4/WO3 core-shell photocatalyst loaded on UiO-66(Ti) for urea photo-oxidation

In this study, a facile four-step hydrothermal method was utilized to deposit a core-shell structure on UiO-66(Zr/Ti) nanoflake (NFs) as a visible-light-driven photocatalyst. The core was magnetic Fe₃O₄ which served as a charge carrier coated with WO₃ shell. The as-prepared photocatalyst was characterized by XRD, VSM, BET, FTIR, FE-SEM, UV-Vis-DRS, and PL techniques which proved successful deposition of Fe₃O₄@WO₃ core/shell particle on UiO-66(Zr/Ti)-NFs. The obtained photocatalyst was subsequently applied for urea photo-oxidation. This magnetically recoverable photocatalyst exhibited superior activity due to its desirable band alignment, high stability, and generation of the photo-induced charge carriers, as well as providing a high surface area with low mass transfer resistance. Fe₃O₄ core acted as charge-carrier to transport the photogenerated charges of UiO-66(Zr/Ti)-NFs (electron-donor) to WO₃ charge-collectors for effective photoconversion. The central composite design was applied to design the experiments matrix in which flow rate, pH, irradiation time, catalyst mass, and initial urea concentration were considered as operational factors. The optimized condition was found by defining the desirability function. 90% degradation percentage was achieved at 550 mL/min solution flowrate, pH = 7, 120 min irradiation time, 0.22 g UiO-66(Zr)-NFs-Fe₃O₄@WO_3, and 40 mg/L of the initial concentration of urea with the desirability value of 0.89. Such a superior photocatalytic activity of UiO-66-Fe₃O₄@WO₃ can be ascribed to the reclamation of Fe₃O₄ as a low bandgap carrier, which accelerated the conveyance of electrons and followed surpassing charge separation. Our present findings open a new strategy to produce a wide range of core-shell heterogeneous catalysts to be applied in photoreactors scale-up.

Chiral poly(amide-imide)/ZnS nanocomposite as a new adsorbent for simultaneous removal of cationic dyes from aqueous solution

A new adsorbent, poly(amide-imide)/zinc sulfide nanocomposite (PAI/ZnS NC), was fabricated and identified by Fourier-transform infrared spectroscopy, X-ray diffraction, energy-dispersive X-ray spectroscopy, field emission-scanning electron microscopy, and transmission electron microscopy. Then, the obtained NC was applied for the simultaneous removal of auramine O (AO) and rhodamine B (RB) dyes from aqueous solution via the interactions of hydrogen bonding, π– π stacking, and Lewis acid–base interaction. The effects of operational variables including pH, PAI/ZnS NC mass, AO and RB concentration, and sonication time on removal efficiency were examined and optimized values were found to be 8.0, 16 mg, 11 mg L−1, and 6 min, respectively. The adsorption capacities of PAI/ZnS NC for the removal of AO and RB dyes were found to be 70.92 and 91.74 mg g−1, respectively. Ultraviolet–visible spectrophotometer was used to determine the amount of residual dye in solution. Fitting the experimental equilibrium data to isotherm models such as Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich reveals the suitability of the Langmuir model with high correlation coefficients ( R2 = 0.998 for AO and R2 = 0.999 for RB). Pseudo-first-order, pseudo-second-order, intraparticle diffusion, and Elovich kinetic models applicability was tested and the pseudo-second-order equation controls the kinetics of the adsorption process. Furthermore, this study establishes that PAI/ZnS NC can be successfully applied as a low-cost adsorbent and conserve its high efficiency after nine cycles for the removal of AO and RB dyes.

Modeling of Degradation of Diazo Dye in Swirl-Flow Photocatalytic Reactor: Response Surface Approach

Photocatalytic degradation of Direct Blue 15 (DB15), an azo dye, was studied using a swirl-flow monolithic reactor under UV irradiation. The degradation reactions were carried out to investigate effects of initial dye concentration, catalyst loading, and light intensity at an optimal pH. The experiments were designed and mathematically modelled by CCD-RSM (central composite design-response surface methodology) approach. It was found that the selected parameters significantly affect DB15 degradation. In terms of the linear term, catalyst loading and light intensity had a synergistic effect, while dye concentration registered the opposite effect. Strong interaction was observed between catalyst loading and both light intensity and initial dye concentration compared with the interaction of light intensity and initial dye concentration. Based on the experimental results, a quadratic model was developed to predict the percentage removal of DB15. The predicted values of the model were in good agreement with the experimental values (R2 = 0.987), indicating the model fits well for the parameter space for which experiments were performed. According to diagnostic plots, the model credibility was valid because its residuals were distributed normally and exhibited a random pattern based on their examination versus the predicted values. The results revealed that the initial dye concentration and catalyst concentration have a significant effect on the mineralization time.

Simultaneous removal of Cd(II) and As(III) by graphene-like biochar-supported zero-valent iron from irrigation waters under aerobic conditions: Synergistic effects and mechanisms

Irrigation water is commonly contaminated with cadmium and arsenic near mining regions, which significantly contributes to excessive heavy metals in rice grains. Herein, we have developed a novel graphene-like biochar (GB)-supported nanoscale zero-valent iron (nZVI) and the underlying mechanisms of synergistic effects between GB and nZVI for the simultaneous removal of Cd(II) and As(III) under aerobic conditions. The results show that GB/nZVI has a high removal capacity of 363 mg/g (nZVI) for As(III) at pH 4 and 92.8 mg/g (nZVI) for Cd(II) at pH 7. These values are significantly higher than GB and nZVI (1.7 times for Cd(II); 1.4 times for As(III)) alone, suggesting strong synergistic effects between GB and nZVI. GB promotes nZVI oxidation to form iron oxyhydroxides and causing 35 % of As(III) converting to As(V). Importantly, As(III) significantly enhance Cd(II) removal by GB/nZVI (i.e., 131.8 mg/g as nZVI). Coexisting ions such as phosphate and humic acid have a stronger inhibitory effect on the simultaneous removal of Cd(II) and As(III). Our results indicate that oxidation and surface complexation are the dominant mechanisms and electrostatic binding exists for As(III) removal, while surface complexation predominates for Cd(II) removal. These findings provide insight into developing an effective solution for removing Cd(II)/As(III) from irrigation waters.

Microwave-assisted urea modified crop residue in Cu2+ scavenging

Raphia hookeri fruit epicarp (RHFE) was used in a novel adsorbent preparation via a combination of urea modification and microwave irradiation. The prepared adsorbent (URHFE) was characterized physicochemically, spectroscopically and microscopically characterized. URHFE efficiency in Cu²⁺ scavenging was tested with focus on operational parameters such as pH, dosage, concentration, contact time, ionic strength and temperature. Adsorption data were tested with isotherms and kinetics models. Optimum adsorption occurred at pH of 5.5. The presence of competing ion decreased Cu²⁺ removal and this varied with competing ion concentration. Cu²⁺ uptake decreased with increase in temperature. Percentage desorption was found generally low. The Langmuir monolayer adsorption capacity (q_max) was obtained to be 144.93 mg/g, this compared well in effectiveness with other adsorbent previously reported. Dubinin Radushkevich (D-R) isotherm model suggests that adsorption mechanism was chemical in nature. Pseudo second order kinetics best described the adsorption kinetics while multilinear adsorption was observed from the intraparticle diffusion model.

Evaluation of curcumin assistance in the antimicrobial and photocatalytic activity of a carbon based TiO2nanocomposite

The present study focuses on the synthesis of visible light active curcumin supported TiO₂/AC (curcumin–TiO₂/AC) through sol–gel and wet impregnation methods for the decolourization of Reactive Blue 160.

As(III) adsorption onto different-sized polystyrene microplastic particles and its mechanism

We systematically investigated the surface characteristics of polystyrene microplastic particles (PSMPs) prepared by ball milling to impart a porous surface structure and special surface characteristics, and studied the mechanism of adsorption of As(III) onto PSMPs. The sizes of the PSMPs prepared by ball milling for 2, 4, and 8 h were in the ranges of 0.1-1, 1-10, and 10-100 μm, respectively. That is, the longer the milling time is, the larger the specific surface area of the particles is. Moreover, the higher the point of zero charge is, the higher the adsorbed amount of As(III) is. The highest adsorption rate of As(III) onto PSMPs was found to be 1.12 mg g^-1. After 1200 min, the adsorption reached equilibrium, and a pseudo-second-order model better fitted the As(III) adsorption kinetics. The Langmuir and Freundlich models could well describe the adsorption isotherms. Furthermore, hydrogen bonds between As(III) and PSMPs were broken at high temperatures, resulting in a decrease in As(III) adsorption onto PSMP, which indicated that the adsorption process was exothermic. Increases in the pH and concentrations of interfering nitrate and phosphate ions in the solution led to inhibited As(III) adsorption of PSMPs. The electrostatic potential of most areas of the PSMP surface was positive, and the H atom on the carboxyl group exhibited a very large positive potential (+56.6 kcal/mol), and thus attracted arsenic oxyanions. Thus, it was determined that As(III) adsorbed to the surface of PSMPs through hydrogen bonding with the carboxyl group. Electrostatic forces and non-covalent interactions are the key mechanisms affecting the adsorption of As(III) onto PSMPs. This work provides a clear theoretical basis for the behavior of the PSMP as an arsenic carrier and might aid to improve the environmental toxicity of arsenic.

Fabrication of a Novel Bifunctional Nanocomposite with Improved Selectivity for Simultaneous Nitrate and Phosphate Removal from Water

Phosphorus and nitrogen compounds are both the main sources of eutrophication and coexist in some municipal effluents or eutrophic waters; elimination of phosphorus and nitrogen from wastewater is becoming an imperative but also a hard task. Herein, an innovative bifunctional nanocomposite HFO@TPR was developed for synchronous nitrate/phosphate elimination from water. A macroporous polystyrene microspheres modified with triethylamine functional groups was synthesized as the host of HFO@TPR for selective nitrate removal, and Fe(III) hydroxide (HFO) nanoparticles were implanted inside as the active species for specific phosphate removal. Compared to other commercial adsorbents, HFO@TPR exhibited outstanding selectivity and preference toward nitrates and phosphates, and the coexisting anions exert an insignificant effect on adsorption performance. Such exceptional bifuntionality of HFO@TPR was achieved through two pathways, that is, nitrate was preferentially adsorbed by the fixed triethylamine groups through the electrostatic attraction, and phosphate was preferentially captured by the encapsulated HFO nanoparticles through the inner-sphere complexation. The exhausted HFO@TPR could be effectively regenerated by using a NaOH-NaCl mixed reagent for cyclic use with a relative constant efficiency. In addition, column adsorption experiments demonstrated that HFO@TPR could eliminate nitrate from 18 to <10 mg N/L with the treatment capacity of ∼600 bed volume (BV), and meanwhile remove phosphate from 2.5 to <0.2 mg P/L with the treatment capacity of ∼750 BV. We believe what we found in this study could advance the method on how to develop bifunctional adsorbents for synchronous removal of coexisting contaminants from water.

Co-adsorption of an anionic dye in the presence of a cationic dye and a heavy metal ion by graphene oxide and photoreduced graphene oxide

To investigate the adsorption behavior of contaminants with different adsorbents and co-adsorbates under identical conditions, the adsorption capacities of anionic orange II (OII) dye onto graphene oxide (GO) and photoreduced GO (PRGO) in a single-component system and in the presence of cationic methylene blue (MB) dye as well as heavy metal ion Pb²⁺ were explored. In this work, PRGO was prepared by solar light irradiation of a GO dispersion. GO and PRGO were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, Raman spectroscopy, atomic force microscopy, scanning electron microscopy, and transmission electron microscopy. The adsorption isotherms of OII, MB, and Pb²⁺ onto GO and PRGO in single and binary systems have been studied and analyzed by the Langmuir model. In the single system, the adsorption capacity of OII on GO can be promoted from 8.4 mg g⁻¹ to 32.5 mg g⁻¹ after solar light irradiation. While the adsorption capacities of MB and Pb²⁺ are not affected by the photoreduction process. In the binary system, a marked synergistic effect for the adsorption of OII has been determined in the presence of both MB and Pb²⁺, where the adsorption capacity of OII on PRGO has been improved from 8.4 mg g⁻¹ to 295 mg g⁻¹ and 105 mg g⁻¹, enhancements of 35- and 12.5-fold, respectively. In contrast, the presence of OII leads to a mildly antagonistic effect on the adsorption of MB and Pb²⁺. These findings show that the adsorption of anionic dyes by graphene-based materials can be strongly improved in the presence of either cationic dyes or heavy metal ions, which will be of great value in practical applications.

The adsorption capacity of graphene oxide (GO) for orange II (OII) can be remarkably enhanced in the presence of methylene blue (MB) and Pb²⁺.

A simple approach for the sonochemical loading of Au, Ag and Pd nanoparticle on functionalized MWCNT and subsequent dispersion studies for removal of organic dyes: Artificial neural network and response surface methodology studies

In this study, the artificial neural network (ANN) and response surface methodology (RSM) based on central composite design (CCD) were applied for modeling and optimization of the simultaneous ultrasound-assisted removal of quinoline yellow (QY) and eosin B (EB). The MWCNT-NH₂ and its composites were prepared by sonochemistry method and characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) analysis's. Initial dyes concentrations, adsorbent mass, sonication time and pH contribution on QY and EB removal percentage were investigated by CCD and replication of experiments at conditions suggested by model has results which statistically are close to experimented data. The ultrasound irradiation is associated with raising mass transfer of process so that small amount of the adsorbent (0.025 g) is able to remove high percentage (88.00% and 91.00%) of QY and EB, respectively in short time (6.0 min) at pH = 6. Analysis of experimental data by conventional models is good indication of Langmuir efficiency for fitting and explanation of experimented data. The ANN based on the Levenberg-Marquardt algorithm (LMA) combined of linear transfer function at output layer and tangent sigmoid transfer function at hidden layer with 20 hidden neurons supply best operation conditions for good prediction of adsorption data. Accurate and efficient artificial neural network was obtained by changing the number of neurons in the hidden layer, while data was divided into training, test and validation sets which contained 70, 15 and 15% of data points respectively. The Average absolute deviation (AAD)% of a collection of 128 data points for MWCNT-NH₂ and composites is 0.58%.for EB and 0.55 for YQ.