Dye removal from water and wastewater by nanosized metal oxides - modified activated carbon: a review on recent researches

Annona glabra L. Seeds: An Agricultural Waste Biosorbent for the Eco-Friendly Removal of Methylene Blue

The seeds of Annona glabra L., an invasive plant in Vietnam, were first employed as a new biosorbent for the adsorption of methylene blue (MB) from aqueous media. The characterizations of the material using FT-IR, SEM, nitrogen adsorption-desorption analysis, and point of zero charge reveals that it possesses a rough and irregular surface, various polar functional groups, and pHpzc of 5.5. Certain adsorption conditions including adsorbent dose, solution pH, contact time, and initial concentration of MB were found to affect adsorption efficiency. The kinetic data are well fitted with pseudo-second-order model with the adsorption rate of 0.002 g mg-1 min-1 and initial rate of 4.46 mg g-1 min-1. For the adsorption isotherm, three nonlinear models were used to analyze the experiment data, including Langmuir, Freundlich, and Temkin. The results indicate that the Langmuir model best describes the adsorption of Annona glabra L. seeds powder (AGSP) with a maximum adsorption capacity of 98.0 mg g-1. The investigation underpins the adsorption mechanism, whereby the electrostatic attraction between positively charged MB and negatively charged surface of AGSP is expected to be the predominant mechanism, together with hydrogen bonding and pi-pi interaction. These results make AGSP an interesting biosorbent concerning its environmental friendliness, cost-effectiveness, and relatively high dye adsorption capacity.

Microwave-assisted synthesis of Vulcan Carbon supported Palladium-Nickel (PdNi@VC) bimetallic nanoparticles, and investigation of antibacterial and Safranine dye removing effects

As an alternative to antibiotics, nanoparticles (NPs) are increasingly being used for targeting bacteria. Nanotechnology holds great potential in the treatment of bacterial infections. Although the mechanisms of antibacterial activity of NPs are not fully understood, widely accepted explanations include oxidative stress induction, metal ion release, and non-oxidative processes. Several simultaneous gene changes would be required in the bacterial cell, making it difficult for bacterial cells to develop resistance to NPs. One important application of nanoparticles is in dye removal. Nanoparticle structures can be utilized effectively as adsorbents due to their reduced size and increased surface area, by combining noble metals, Palladium-Nickel (Pd-Ni), with a carbon structure known as Vulcan Carbon (VC), it is anticipated that the consumption of precious metals can be reduced while benefiting from the enhanced properties of the bimetallic structure. The PdNi@VC structure was synthesized using the microwave synthesis technique. Characterization techniques such as Transmission Electron Microscope (TEM) and X-Ray diffraction (XRD) were employed to confirm the formation of the bimetallic structure. According to the Debye-Scherrer equation, the size is 2.74 nm. In addition, photodegradation assays using simulator solar radiation yielded 67% efficacy against Safranine dye. In addition, The PdNi@VC had a high percentage of bacterial inhibition at the concentration of 200 g/ml against Staphylococcus aureus (S.aureus), and Escherichia coli (E.coli). This study focuses on the synthesis of bimetallic nanoparticles for antibacterial applications and investigates their effectiveness in dye removal from wastewater. The obtained results provide valuable insights for the implementation of innovative methods in these areas.

Cellulose nanofibers decorated with SiO2 nanoparticles: Green adsorbents for removal of cationic and anionic dyes; kinetics, isotherms, and thermodynamic studies

Cellulose nanofibers decorated with SiO2 nanoparticles (SiO2-CNF) were prepared by the extraction of cellulose nanofibers from Yucca leaves, followed by modification with SiO2 nanoparticles, and used as efficient materials for the removal of both anionic and cationic dyes from the aqueous solution. Prepared nanostructures were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction powder (XRD), Thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy dispersive X-ray (EDX), and transmission electron microscopy (TEM) analysis. The adsorption capacity of the nanostructures was investigated for the removal of both cationic (Methylene Blue, MB, and Crystal Violet, CV) and anionic (Eriochrome Black-T, EB) dyes. The kinetics of adsorption were investigated using some well-known models, including intraparticular diffusion (IPD), pseudo-first-order (PFO), pseudo-second-order (PSO), and Elovich. The adsorption isotherms were also explored using the Langmuir, Freundlich, Temkin, and Redlich-Peterson models. The obtained results revealed that the adsorption processes follow PSO kinetic and Langmuir isotherm models. Thermodynamic parameters of the adsorption were measured at different temperatures, indicating the feasibility and spontaneity of the adsorption. The pH and salt effects on adsorption were also explored. Finally, according to the reusability tests, the prepared adsorbents showed high recoverability without considerable loss in adsorption efficiency after five repeated runs.

In vitro analysis of green synthesized CuO nanoparticles using Tanacetum parthenium extract for multifunctional applications

Tanacetum parthenium L. is a popular traditional medicinal plant that the role of presence of particular phytochemical compounds are still unconsidered particularly in the bio-nano researches. Here, for the first time, the green fabrication of CuO NPs using Tanacetum parthenium L. extract was performed and assessed for the antimicrobial, cytotoxicity, and dye degradation activities. Characterization of CuO NPs was done by UV-visible spectra, XRD, FT-IR, TEM, and EDX. The synthesized CuO NPs possess a crystalline nature, a functional group that resembles T. parthenium, with a spherical shape particle with an average size of 28 nm. EDX confirmed CuO NPs formation. The CuO NPs showed excellent antimicrobial activity against tested microorganisms. The cytotoxicity of CuO NPs was demonstrated the concentration-dependent inhibition of the growth against both cancer and normal cell lines. The results exhibited concentration-dependent inhibition of the growth of Hela, A 549, and MCF7 cancer cells (IC₅₀ = 65.0, 57.4, and 71.8 µg/mL, respectively), which were statistically significant comparing control cells (IC₅₀ = 226.1 µg/mL). Furthermore, we observed that CuO NPs-induced programmed cell death in the cancer cells were mediated with the downregulation of Bcl2 and upregulation of bax, caspase-3. CuO NPs were verified to be a superb catalyst as they had excellent activity for the degradation of 99.6%, 98.7%, 96.6%, and 96.6% of Congo red, methylene blue, methylene orange, and rhodamine B as industrial dyes in 3, 6.5, 6.5, and 6.5 min, respectively. Overall, the present study nominates T. parthenium as a proper bio-agent in the biosynthesis of CuO NPs with powerful catalytic and antimicrobial activities as well as a cancer treatment.

Facile fabrication of three-dimensional nanofibrous foams of cellulose@g-C3N4@Cu2O with superior visible-light photocatalytic performance

In this work, a unique three-dimensional nanofibrous foam of cellulose@g-C₃N₄@Cu₂O was prepared via electrospinning followed by a foaming process. A cellulose solution in DMAc/LiCl containing g-C₃N₄ and CuSO₄ was applied for electrospinning, while aqueous alkali was used as the coagulation bath. The solidification of electrospun cellulose/g-C₃N₄ nanofibers would be accompanied with in-situ formation of Cu(OH)₂ nanoparticles. Interestingly, the hydrogen gas (H₂) generated from NaBH₄ could transform the two-dimensional membrane into a three-dimensional foam, leading to the increased specific surface area and porosity of the material. Meanwhile, the Cu(OH)₂ nanoparticles attached on the electrospun nanofibers were reduced to Cu₂O to form a p-n heterostructure between Cu₂O and g-C₃N₄. The as-prepared cellulose@g-C₃N₄@Cu₂O foam exhibited a high degradation efficiency (99.5 %) for the dye of Congo Red under visible light radiation. And ·O^2- was discovered to be the dominant reactive species responsive for dye degradation. Moreover, the cellulose@g-C₃N₄@Cu₂O could maintain its initial degradation efficiency even after seven cycles of reuse, suggesting the excellent stability and cycling performance.

Emerging Modification Technologies of Lignin-based Activated Carbon toward Advanced Applications

Lignin-based activated carbon (LAC) is a promising high-quality functional material due to high surface area, abundant porous structure, and various functional groups. Modification is the most important step to functionalize LAC by altering its porous and chemical properties. This Review summarizes the state-of-the-art modification technologies of LAC toward advanced applications. Promising modification approaches are reviewed to display their effects on the preparation of LAC. The multiscale changes in the porosity and the surface chemistry of LAC are fully discussed. Advanced applications are then introduced to show the potential of LAC for supercapacitor electrode, catalyst support, hydrogen storage, and carbon dioxide capture. Finally, the mechanistic structure-function relationships of LAC are elaborated. These results highlight that modification technologies play a special role in altering the properties and defining the functionalities of LAC, which could be a promising porous carbon material toward industrial applications.

Modified Beaded Materials from Recycled Wastes of Bagasse and Bagasse Fly Ash with Iron(III) Oxide-Hydroxide and Zinc Oxide for the Removal of Reactive Blue 4 Dye in Aqueous Solution

Dye contamination in wastewater affects the photosynthesis of aquatic plants and algae by blocking the sunlight, and it induces toxicity to aquatic organisms, which might result in human health effects. Thus, the treatment of dyes in wastewater is required before discharging into the receiving water for safety purposes. Six dye adsorbent materials bagasse beads (BB), bagasse fly ash beads (BFB), bagasse beads with mixed iron(III) oxide-hydroxide (BBF), bagasse fly ash beads with mixed iron(III) oxide-hydroxide (BFBF), bagasse beads with mixed zinc oxide (BBZ), and bagasse fly ash beads with mixed zinc oxide (BFBZ) were synthesized and investigated using various characterization techniques such as X-ray diffractometry (XRD), field emission scanning electron microscopy with focused ion beam (FESEM-FIB), energy dispersive X-ray spectrometry (EDX), and Fourier transform infrared spectroscopy (FTIR). A series of batch experiments on the effects of dosage (0.5-3 g), contact time (3-18 h), temperature (30-80°C), pH (3-11), and initial concentration (30-90 mg/L) were used to investigate reactive blue 4 (RB4) dye removal efficiencies in aqueous solution, and their adsorption isotherms and kinetics were studied for explaining their adsorption patterns and mechanisms. All dye adsorbent materials demonstrated semicrystalline structures, and their surface morphologies had a spherical shape with coarse surfaces. Five main elements of oxygen, carbon, calcium, chlorine, and sodium and six main functional groups of alcohol and carboxylic acid (O-H), carbon dioxide (O=C=O), aromatic groups (C=O and N=O), alkene (C-H), and sodium alginate (C-O-C) were detected in all dye adsorbent materials. For batch tests, they could remove RB4 dye by more than 90%, and BFBF exhibited the highest RB4 dye removal efficiency at 99.36%. Freundlich and pseudo-second-order kinetic models well explained their adsorption patterns and mechanisms, in which BFBF demonstrated a higher maximum adsorption capacity (q _m) of 10.277 mg/g than that of other dye adsorbent materials. Therefore, all dye adsorbent materials offer good potential for further industrial applications.

Transformation of industrial and organic waste into titanium doped activated carbon - cellulose nanocomposite for rapid removal of organic pollutants

Production of cost-efficient composite materials with desired physicochemical properties from low-cost waste material is much needed to meet the growing needs of the industrial sector. As a step forward, the current study reports for the first time an effective utilization of industrial metal (inorganic) waste as well as fall leaves (organic waste), to produce three types of nanomaterials at the same time; "Titanium Doped Activated Carbon Nanostructures (Ti-ACNs)", "Nanocellulose (NCel)", and combination of both "Titanium Doped Activated Carbon Cellulose Nanocomposite (Ti-AC-Cel-NC)". X-ray diffraction (XRD), transmission electron microscopy (TEM) and microanalysis (EDXS) measurements reveal that the Ti-ACNs material is formed by Ti-nanostructures, generally poorly crystalized but in some cases forming hexagonal Ti-crystallites of 15 nm, embedded in mutated graphene clouds. Micro- Fourier transform infrared spectroscopy (micro-FTIR) confirms that the chemical structure of NCel with bond vibrations between 1035 to 2917 cm^-1 remained preserved during Ti-AC-Cel-NC formation. The prepared materials (Ti-ACNs, Ti-AC-Cel-NC) have demonstrated rapid removal of organic pollutants (Crystal Violet, Methyl Violet) from wastewater through surface adsorption and photocatalysis. In the first 20 min, Ti-ACNs have adsorbed ≈87% of the organic pollutants and further photocatalyzed them up to ≈96%. When Ti-ACNs are combined with NCel, their efficiency is increased of about four times. This performance originates from the adsorption by mutated graphene-like carbon and assisted photocatalysis by Ti nanostructures as well as the good supporting capacity of NCel for the homogenous Ti-ACNs distribution.

A resin containing motifs of maleic acid and glycine: a super-adsorbent for adsorptive removal of basic dye pararosaniline hydrochloride and Cd(II) from water

The cyclocopolymerization of N,N-diallylglycine hydrochloride, maleic acid and 1,1,4,4-tetraallylpiperazinium dichloride afforded a cross-linked polyzwitterionic acid, which, upon treatment with NaOH, gave the corresponding cross-linked anionic polyelectrolyte (CAPE) in quantitative yield. The pH-responsive resins contained a high density of CO2 - motifs as well as the chelating motifs of glycine residues. The resin CAPE was found to be a super-adsorbent for the removal of pararosaniline hydrochloride (PRH); having a q max of 1534 mg/g. The adsorption process followed pseudo-second-order kinetics and was found to be a nearly irreversible process as suggested by the parameters obtained from Elovich kinetic model. The resin demonstrated excellent adsorption/desorption efficiencies, thereby ensuring its recycling and reuse in potent applications like remediation of industrial dye-waste water. The resin's chelating motifs were also efficient in the adsorptive removal of Cd(II) ions with a q max of 248 mg/g. It was also employed for the simultaneous and effective trapping of Cd(II) and the dye from industrial wastewater. The resin's impressive performance accords it a prestigious place among many sorbents in recent works.

Decontamination of fenitrothion from aqueous solutions using rGO/MoS2/Fe3O4 magnetic nanosorbent: synthesis, characterization and removal application

In the present work, rGO/MoS2/Fe3O4 nanocomposite was synthesized and after confirmation of the structure by FTIR, XRD, and FESEM techniques, its performance as nanosorbent was investigated for the removal of fenitrothion pesticide from the aqueous media. The parameters affecting the removal process including agitation time, pH of the reaction medium, adsorbent content, initial analyte concentration as well as desorption parameters were investigated and optimized. Under optimum conditions (pH = 7, adsorbent amount: 30 mg, adsorption and desorption time: 5 min, eluent type and volume: 0.01 M ethanol-acetic acid and 4 mL), the synthesized adsorbent was able to remove fenitrothion pesticide up to 98% with an adsorption capacity of 33.4 mg/g. By investigation of the line equation and the correlation coefficient value, it was found that the adsorption process, in this study, follows the Langmuir model.

Statistical Modeling and Kinetic Studies on the Adsorption of Reactive Red 2 by a Low-Cost Adsorbent: Grape Waste-Based Activated Carbon Using Sulfuric Acid Activator-Assisted Thermal Activation

The efficiency of activated carbon produced from grape waste as a low-cost, nontoxic, and available adsorbent to remove Reactive Red 2 from aqueous solution has been investigated. The prepared activated carbon has been characterized by FTIR, SEM, and BET. The results of characterization indicate the successful conversion of grape waste into mesoporous AC with desirable surface area consist of different functional groups. The results of statistical modeling displayed high $R^2$ value of 0.97% for dye removal that shows the developed model has acceptable accuracy. The effect of independent variables indicated that the highest adsorption (96.83%) obtained at pH 3, adsorbent dosage of 12.25 g/L, and initial dye concentration of 100 mg/L when the adsorption time was 90 min. The results of isotherms modeling showed that the data fit well with the Langmuir (type II). The kinetic studies using pseudofirst-order and pseudosecond-order models pointed out that the type (I) of pseudosecond-order kinetic model provided the best fit to the adsorption data. Parameters of thermodynamics including Gibbs energy ( $\Delta G^{°}$ ) and $k_{\text{o}}$ were calculated. The values of $\Delta G^{°}$ indicated that the dye adsorption of RR2 is spontaneous. The agricultural wastes due to special points such as low-cost, availability, and high ability to produce an adsorbent with high efficiency to remove dye can be proposed for water and wastewater treatment.

Biodegradable polymers and their nano-composites for the removal of endocrine-disrupting chemicals (EDCs) from wastewater: A review

Endocrine-disrupting chemicals (EDCs) target the endocrine system by interfering with the natural hormones in the body leading to adverse effects on human and animal health. These chemicals have been identified as major polluting agents in wastewater effluents. Pharmaceuticals, personal care products, industrial compounds, pesticides, dyes, and heavy metals are examples of substances that could be considered endocrine active chemicals. In humans, these chemicals could cause obesity, cancer, Alzheimer's disease, autism, reproductive abnormalities, and thyroid problems. While in wildlife, dysfunctional gene expression could lead to the feminization of some aquatic organisms, metabolic diseases, cardiovascular risk, and problems in the reproductive system as well as its levels of hatchability and vitellogenin. EDCs could be effectively removed from wastewater using advanced technologies such as reverse osmosis, membrane treatment, ozonation, advanced oxidation, filtration, and biodegradation. However, adsorption has been proposed as a more promising and sustainable method for water treatment than any other reported technique. Increased attention has been paid to biodegradable polymers and their nano-composites as promising adsorbents for the removal of EDCs from wastewater. These polymers could be either natural, synthetic, or a combination of both. This review presents a summary of the most relevant cases where natural and synthetic biodegradable polymers have been used for the successful removal of EDCs from wastewater. It demonstrates the effectiveness of these polymers as favorable adsorbents for novel wastewater treatment technologies. Hitherto, very limited work has been published on the use of both natural and synthetic biodegradable polymers to remove EDCs from wastewater, as most of the studies focused on the utilization of only one type, either natural or synthetic. Therefore, this review could pave the way for future exploration of biodegradable polymers as promising and sustainable adsorbents for the removal of various types of pollutants from wastewater.

Factors Affecting Synthetic Dye Adsorption; Desorption Studies: A Review of Results from the Last Five Years (2017-2021)

The primary, most obvious parameter indicating water quality is the color of the water. Not only can it be aesthetically disturbing, but it can also be an indicator of contamination. Clean, high-quality water is a valuable, essential asset. Of the available technologies for removing dyes, adsorption is the most used method due to its ease of use, cost-effectiveness, and high efficiency. The adsorption process is influenced by several parameters, which are the basis of all laboratories researching the optimum conditions. The main objective of this review is to provide up-to-date information on the most studied influencing factors. The effects of initial dye concentration, pH, adsorbent dosage, particle size and temperature are illustrated through examples from the last five years (2017-2021) of research. Moreover, general trends are drawn based on these findings. The removal time ranged from 5 min to 36 h (E = 100% was achieved within 5-60 min). In addition, nearly 80% efficiency can be achieved with just 0.05 g of adsorbent. It is important to reduce adsorbent particle size (with Φ decrease E = 8-99%). Among the dyes analyzed in this paper, Methylene Blue, Congo Red, Malachite Green, Crystal Violet were the most frequently studied. Our conclusions are based on previously published literature.

PEG/Sodium Tripolyphosphate-Modified Chitosan/Activated Carbon Membrane for Rhodamine B Removal

Textile dyes from wastewater effluent are highly toxic to both living species and aqueous environments. An environmentally friendly method to remove hazardous dyes from wastewater in the textile industry has been a challenge. Chitosan (CS) and activated carbon (AC) are widely used as adsorbents for dye removal. However, the poor porosity and unsatisfactory stability of CS and the unfriendly cost of AC limited their applications to be used alone as a single adsorbent. Here, we report a novel method to prepare a CS/AC membrane using PEG10000 as a porogen and sodium tripolyphosphate (TPP) as a cross-linking agent. The adsorption efficiency and reusability of the PEG/TPP-modified CS/AC membrane to remove RhB were investigated based on dynamic and static adsorption models. The results reveal that the adsorption performance of CS/AC membranes was significantly improved after the PEG/TPP modification based on the abundance macroporous structure. The modified CS/AC membrane with a 30% AC doping ratio exhibited an excellent adsorption efficiency of 91.29 and 73.91% in the dynamic and static adsorption processes, respectively. These results provide new insights into designing membranes to remove dyes from wastewater efficiently.

Sustainable Removal of Contaminants by Biopolymers: A Novel Approach for Wastewater Treatment. Current State and Future Perspectives

Naturally occurring substances or polymeric biomolecules synthesized by living organisms during their entire life cycle are commonly defined as biopolymers. Different classifications of biopolymers have been proposed, focusing on their monomeric units, thus allowing them to be distinguished into three different classes with a huge diversity of secondary structures. Due to their ability to be easily manipulated and modified, their versatility, and their sustainability, biopolymers have been proposed in different fields of interest, starting from food, pharmaceutical, and biomedical industries, (i.e., as excipients, gelling agents, stabilizers, or thickeners). Furthermore, due to their sustainable and renewable features, their biodegradability, and their non-toxicity, biopolymers have also been proposed in wastewater treatment, in combination with different reinforcing materials (natural fibers, inorganic micro- or nano-sized fillers, antioxidants, and pigments) toward the development of novel composites with improved properties. On the other hand, the improper or illegal emission of untreated industrial, agricultural, and household wastewater containing a variety of organic and inorganic pollutants represents a great risk to aquatic systems, with a negative impact due to their high toxicity. Among the remediation techniques, adsorption is widely used and documented for its efficiency, intrinsic simplicity, and low cost. Biopolymers represent promising and challenging adsorbents for aquatic environments’ decontamination from organic and inorganic pollutants, allowing for protection of the environment and living organisms. This review summarizes the results obtained in recent years from the sustainable removal of contaminants by biopolymers, trying to identify open questions and future perspectives to overcome the present gaps and limitations.