Enhanced heavy metals removal by a novel carbon nanotubes buckypaper membrane containing a mixture of two biopolymers: Chitosan and i-carrageenan

Carbon nanotubes buckypapers: A new frontier in wastewater treatment technology

Occurrence of contaminants in water is one of the major global concerns humanity is still facing today: most of them are extremely toxic and dangerous for human health, obliging their removal for a proper and correct process of sanitation. Among wastewater treatment technologies, in the view of development of sustainable and environmentally friendly processes, membrane adsorption has proved to be a fast and simple method in the removal of pollutants, offering great contaminants recovery percentages, fast adsorbent regeneration and recycle, and easy scale-up. Due to their large surface area and tunable chemistry, carbon nanotubes (CNTs)-based materials revealed to be extraordinary adsorbents, exceeding by far performances of ordinary organic and inorganic membranes such as polyethersulfone, polyvinylidene fluoride, polytetrafluoroethylene, ceramics, currently employed in membrane technologies for wastewater treatment. In consideration of this, the review aims to summarize recent developments in the field of carbon nanotubes-based materials for pollutants recovery from water through adsorption processes. After a brief introduction concerning what adsorption phenomenon is and how it is performed and governed by using carbon nanotubes-based materials, the review discusses into detail the employment of three common typologies of CNTs-based materials (CNTs powders, CNTs-doped polymeric membranes and CNTs membranes) in adsorption process for the removal of water pollutants. Particularly focus will be devoted on the emergent category of self-standing CNTs membranes (buckypapers), made entirely of carbon nanotubes, exhibiting superior performances than CNTs and CNTs-doped polymeric membranes in terms of preparation strategy, recovery percentages of pollutants and regeneration possibilities. The extremely encouraging results presented in this review aim to support and pave the way to the introduction of alternative and more efficient pathways in wastewater treatment technologies to contrast the problem of water pollution.

Macroalgae Bioplastics: A Sustainable Shift to Mitigate the Ecological Impact of Petroleum-Based Plastics

The surge in global utilization of petroleum-based plastics, which notably heightened during the COVID-19 pandemic, has substantially increased its harm to ecosystems. Considering the escalating environmental impact, a pivotal shift towards bioplastics usage is imperative. Exploring and implementing bioplastics as a viable alternative could mitigate the ecological burden posed by traditional plastics. Macroalgae is a potential feedstock for the production of bioplastics due to its abundance, fast growth, and high cellulose and sugar content. Researchers have recently explored various methods for extracting and converting macroalgae into bioplastic. Some of the key challenges in the production of macroalgae bioplastics are the high costs of large-scale production and the need to optimize the extraction and conversion processes to obtain high-quality bioplastics. However, the potential benefits of using macroalgae for bioplastic production include reducing plastic waste and greenhouse gas emissions, using healthier materials in various life practices, and developing a promising area for future research and development. Also, bioplastic provides job opportunities in free enterprise and contributes to various applications such as packaging, medical devices, electronics, textiles, and cosmetics. The presented review aims to discuss the problem of petroleum-based plastic, bioplastic extraction from macroalgae, bioplastic properties, biodegradability, its various applications, and its production challenges.

Aminothiol supported dialdehyde cellulose for efficient and selective removal of Hg(II) from aquatic solutions

The increasingly serious problem of mercury pollution has caused wide concern, and exploring adsorbent materials with high adsorption capacity is a simple and effective approach to address this concern. In the recent study, dialdehyde cellulose (DAC), cyanoacetohydrazide (CAH), and carbon disulfide (CS2) are used as raw materials for the (DAC@CAH@SK2) preparation material through the three-steps method. By utilizing the following characterization techniques; thermogravimetric analysis (TGA), N2 adsorption-desorption isotherm (BET), elemental analysis, scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), 1HNMR and Energy Dispersive X-ray Spectroscopy (EDS) of DAC@CAH@SK2 composite. The point of zero charge (pHPZC) for the prepared DAC@CAH@SK2 also was examined. From the batch experiments, the optimum conditions were found to be pH (5-8), an Hg2+ concentration of 150 mg/L, a DAC@CAH@SK2 dose of 0.01 g, and a contact time of 180 min with a maximum adsorption quantity of 139.6 mg/g. The process of Hg2+ adsorption on the DAC@CAH@SK2 material was spontaneous exothermic, monolayer chemisorption, and well-fitted to Langmuir and pseudo-2nd-order models. The DAC@CAH@SK2 selectivity towards the Hg2+ was examined by investigating the interfering metal ions effect. The DAC@CAH@SK2 was successfully applied for the Hg2+ removal from synthetic effluents and real wastewater samples with a recovery % exceeding 95%. The prepared DAC@CAH@SK2 was regenerated using a mixture of EDTA and thiourea. Also, FT-IR analysis indicates that the synergistic complexation of N and S atoms on DAC@CAH@SK2 with Hg(II) is an essential factor leading to the high adsorption capacity.

Development, Characterization, and Burn Wound-Healing Potential of Neomycin-Loaded Clay-Reinforced Nanofibers

Background: Skin wounds affect millions of individuals around the world, and their treatment is expensive. Objective: The purpose of this study was to make neomycin-loaded CG/PVA/PAN (NCPP) nanofibers to improve wound healing. Methods: The NCPP nanofibers were characterized by using thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy, and X-ray diffraction. Drug solubility, dissolution, swelling ratio, erosion, and antibacterial studies were performed. The in vivo wound healing study of nanofibers was performed in a rabbit model and was supported by % age wound closure and histopathology. Results: The results of SEM showed some sort of agglomeration on the surface of fibers, while TGA showed 10% more stability for drug-loaded nanofibers. The drug permeation study indicated that the formulation with 15% PVA showed a controlled release profile of the drug. The NCPP nanofibers had an appreciable water retention capability. The NCPP nanofibers showed appreciable antibacterial activity against Enterococcus faecalis (Gram-positive bacteria) and Klebsiella pneumonia (Gram-negative bacteria). The wound healing study showed the better healing properties of NCPP nanofibers within 15 days. Conclusion: The findings helped us to conclude that the NCPP nanofibers were successfully fabricated and found to have a promising role in infected wound healing.

Progresses in lignin, cellulose, starch, chitosan, chitin, alginate, and gum/carbon nanotube (nano)composites for environmental applications: A review

Water sources are becoming increasingly scarce, and they are contaminated by industrial, residential, and agricultural waste-derived organic and inorganic contaminants. These contaminants may pollute the air, water, and soil in addition to invading the ecosystem. Because carbon nanotubes (CNTs) can undergo surface modification, they can combine with other substances to create nanocomposites (NCs), including biopolymers, metal nanoparticles, proteins, and metal oxides. Furthermore, biopolymers are significant classes of organic materials that are widely used for various applications. They have drawn attention due to their benefits such as environmental friendliness, availability, biocompatibility, safety, etc. As a result, the synthesis of a composite made of CNT and biopolymers can be very effective for a variety of applications, especially those involving the environment. In this review, we reported environmental applications (including removal of dyes, nitro compounds, hazardous materialsو toxic ions, etc.) of composites made of CNT and biopolymers such as lignin, cellulose, starch, chitosan, chitin, alginate, and gum. Also, the effect of different factors such as the medium pH, the pollutant concentration, temperature, and contact time on the adsorption capacity (AC) and the catalytic activity of the composite in the reduction or degradation of various pollutants has been systematically explained.

Green and Superior Adsorbents Derived from Natural Plant Gums for Removal of Contaminants: A Review

The ubiquitous presence of contaminants in water poses a major threat to the safety of ecosystems and human health, and so more materials or technologies are urgently needed to eliminate pollutants. Polymer materials have shown significant advantages over most other adsorption materials in the decontamination of wastewater by virtue of their relatively high adsorption capacity and fast adsorption rate. In recent years, "green development" has become the focus of global attention, and the environmental friendliness of materials themselves has been concerned. Therefore, natural polymers-derived materials are favored in the purification of wastewater due to their unique advantages of being renewable, low cost and environmentally friendly. Among them, natural plant gums show great potential in the synthesis of environmentally friendly polymer adsorption materials due to their rich sources, diverse structures and properties, as well as their renewable, non-toxic and biocompatible advantages. Natural plant gums can be easily modified by facile derivatization or a graft polymerization reaction to enhance the inherent properties or introduce new functions, thus obtaining new adsorption materials for the efficient purification of wastewater. This paper summarized the research progress on the fabrication of various gums-based adsorbents and their application in the decontamination of different types of pollutants. The general synthesis mechanism of gums-based adsorbents, and the adsorption mechanism of the adsorbent for different types of pollutants were also discussed. This paper was aimed at providing a reference for the design and development of more cost-effective and environmentally friendly water purification materials.

Development of Functional Hybrid Polymers and Gel Materials for Sustainable Membrane-Based Water Treatment Technology: How to Combine Greener and Cleaner Approaches

Water quality and disposability are among the main challenges that governments and societies will outside during the next years due to their close relationship to population growth and urbanization and their direct influence on the environment and socio-economic development. Potable water suitable for human consumption is a key resource that, unfortunately, is strongly limited by anthropogenic pollution and climate change. In this regard, new groups of compounds, referred to as emerging contaminants, represent a risk to human health and living species; they have already been identified in water bodies as a result of increased industrialization. Pesticides, cosmetics, personal care products, pharmaceuticals, organic dyes, and other man-made chemicals indispensable for modern society are among the emerging pollutants of difficult remediation by traditional methods of wastewater treatment. However, the majority of the currently used waste management and remediation techniques require significant amounts of energy and chemicals, which can themselves be sources of secondary pollution. Therefore, this review reported newly advanced, efficient, and sustainable techniques and approaches for water purification. In particular, new advancements in sustainable membrane-based filtration technologies are discussed, together with their modification through a rational safe-by-design to modulate their hydrophilicity, porosity, surface characteristics, and adsorption performances. Thus, their preparation by the use of biopolymer-based gels is described, as well as their blending with functional cross-linkers or nanofillers or by advanced and innovative approaches, such as electrospinning.

Preparation and Characterization of Modified Polysulfone with Crosslinked Chitosan-Glutaraldehyde MWCNT Nanofiltration Membranes, and Evaluation of Their Capability for Salt Rejection

Nanofiltration membranes were successfully created using multi-walled carbon nanotubes (MWCNTs) and MWCNTs modified with amine (MWCNT-NH2) and carboxylic groups (MWCNT-COOH). Chitosan (CHIT) and chitosan−glutaraldehyde (CHIT-G) were utilized as dispersants. Sonication, SEM, and contact angle were used to characterize the as-prepared membranes. The results revealed that the type of multi-walled carbon nanotubes (MWCNT, MWCNT-COOH and MWCNT-NH2) used as the top layer had a significant impact on membrane characteristics. The lowest contact angle was 38.6 ± 8.5 for the chitosan-G/MWCNT-COOH membrane. The surface morphology of membranes changed when carbon with carboxylic or amine groups was introduced. In addition, water permeability was greater for CHIT-G/MWCNT-COOH and CHIT-G/MWCNT-NH2 membranes. The CHIT-G/MWCNT-COOH membrane had the highest water permeability (5.64 ± 0.27 L m−2 h−1 bar−1). The findings also revealed that for all membranes, the rejection of inorganic salts was in the order R(NaCl) > R(MgSO4).

Recent advances in biopolymer-based advanced oxidation processes for dye removal applications: A review

Over the past few years, synthetic dye-contaminated wastewater has attracted considerable global attention due to the low biodegradability and the ability of organic dyes to persist and remain toxic, causing numerous health and environmental concerns. As a result of the recalcitrant nature of those complex organic dyes, the remediation of wastewater using conventional wastewater treatment techniques is becoming increasingly challenging. In recent years, advanced oxidation processes (AOPs) have emerged as a potential alternative to treat organic dyestuffs discharged from industries. The most widely employed AOPs include photocatalysis, ozonation, Fenton oxidation, electrochemical oxidation, catalytic heterogeneous oxidation, and ultrasound irradiation. These processes involve the generation of highly reactive radicals to oxidize organic dyes into innocuous minerals. However, many conventional AOPs suffer from several setbacks, including the high cost, high consumption of reagents and substrates, self-agglomeration of catalysts, limited reusability, and the requirement of light, ultrasound, or electricity. Therefore, there has been significant interest in improving the performance of conventional AOPs using biopolymers and heterogeneous catalysts such as metal oxide nanoparticles (MONPs). Biopolymers have been widely considered in developing green, sustainable, eco-friendly, and low-cost AOP-based dye removal technologies. They inherit intriguing properties like biodegradability, renewability, nontoxicity, relative abundance, and sorption. In addition, the immobilization of catalysts on biopolymer supports has been proven to possess excellent catalytic activity and turnover numbers. The current review provides comprehensive coverage of different AOPs and how efficiently biopolymers, including cellulose, chitin, chitosan, alginate, gelatin, guar gum, keratin, silk fibroin, zein, albumin, lignin, and starch, have been integrated with heterogeneous AOPs in dye removal applications. This review also discusses the general degradation mechanisms of AOPs, applications of biopolymers in AOPs and the roles of biopolymers in AOPs-based dye removal processes. Furthermore, key challenges and future perspectives of biopolymer-based AOPs have also been highlighted.

Removal of Non-Steroidal Anti-Inflammatory Drugs from Drinking Water Sources by GO-SWCNT Buckypapers

Pharmaceutical products such as antibiotics, analgesics, steroids, and non-steroidal anti-inflammatory drugs (NSAIDs) are new emerging pollutants, often present in wastewater, potentially able to contaminate drinking water resources. Adsorption is considered the cheapest and most effective technique for the removal of pollutants from water, and, recently, membranes obtained by wet filtration method of SWCNT aqueous solutions (SWCNT buckypapers, SWCNT BPs) have been proposed as self-standing porous adsorbents. In this paper, the ability of graphene oxide/single-walled carbon nanotube composite membranes (GO-SWCNT BPs) to remove some important NSAIDs, namely Diclofenac, Ketoprofen, and Naproxen, was investigated at different pH conditions (pH 4, 6, and 8), graphene oxide amount (0, 20, 40, 60, and 75 wt.%), and initial NSAIDs concentration (1, 10, and 50 ppm). For the same experimental conditions, the adsorption capacities were found to strongly depend on the graphene oxide content. The best results were obtained for 75 wt.% graphene oxide with an adsorption capacity of 118 ± 2 mg g^-1 for Diclofenac, 116 ± 2 mg g^-1 for Ketoprofen, and 126 ± 3 mg g^-1 for Naproxen at pH 4. Overall, the reported data suggest that GO-SWCNT BPs can represent a promising tool for a cheap and fast removal of NSAIDs from drinking water resources, with easy recovery and reusability features.

Carbon-based adsorbents as proficient tools for the removal of heavy metals from aqueous solution: A state of art-review emphasizing recent progress and prospects

Carbon-centric adsorbents (CCA) are diverse forms, from simple biochar (BC) to graphene derivatives, carbon nanotubes (CNTs), and activated carbon (AC), which have been vastly explored for their removal of a plethora of pollutants, including heavy metals (HM). The prominent features of CCA are their operational attributes like extensive surface area, the occurrence of flexible surface functional groups, etc. This work offers a comprehensive examination of contemporary research on CCA for their superior metal removal aptitude and performances in simulated solutions and wastewater flows; via portraying the recent research advances as an outlook on the appliances of CACs for heavy metal adsorption for removal via distinct forms like AC, BC, Graphene oxide (GO), and CNTs. The bibliometric analysis tool was employed to highlight the number of documents, country-wise contribution, and co-occurrence mapping based on the Scopus database. The coverage of research works in this review is limited to the last 5 years (2017-2021) to highlight recent progress and prospects in using CCAs such as AC, BC, GO, and CNTs to remove HM from aqueous media, which makes the review unique. Besides an overview of the common mechanisms of CACs, the future scope of CAC, especially towards HM mitigation, is also discussed in this review. This review endorses that further efforts should be commenced to enhance the repertory of CCAs that effectively eliminate multiple targeted metals in both simulated and real wastewater.

Review on biopolymers and composites - Evolving material as adsorbents in removal of environmental pollutants

The presence of pollutants and toxic contaminants in water sources makes it unfit to run through. Though various conventional techniques are on deck, development of new technologies are vital for wastewater treatment and recycling. Polymers have been intensively utilized recently in many industries owing to their unique characteristics. Biopolymers resembles natural alternative to synthetic polymers that can be prepared by linking the monomeric units covalently. Despite the obvious advantages of biopolymers, few reviews have been conducted. This review focuses on biopolymers and composites as suitable adsorbent material for removing pollutants present in environment. The classification of biopolymers and their composites based on the sources, methods of preparation and their potential applications are discussed in detail. Biopolymers have the potentiality of substituting conventional adsorbents due to its unique characteristics. Biopolymer based membranes and effective methods of utilization of biopolymers as suitable adsorbent materials are also briefly elaborated. The mechanism of biopolymers and their membrane-based adsorption has been briefly reviewed. In addition, the methods of regeneration and reuse of used biopolymer based adsorbents are highlighted. The comprehensive content on fate of biopolymer after adsorption is given in brief. Finally, this review concludes the future investigations in recent trends in application of biopolymer in various fields in view of eco-friendly and economic perspectives.

Amine-bilayer-functionalized cellulose-chitosan composite hydrogel for the efficient uptake of hazardous metal cations and catalysis in polluted water

Herein, we represent a novel ecofriendly bilayer-amine group incorporated microcrystalline cellulose (MCC)/chitosan (CS) hydrogel, fabricated via integrating polydopamine (PDA) and polyethyleneimine (PEI) for reliable and effective extraction of copper (Cu²⁺), zinc (Zn²⁺), and nickel (Ni²⁺) ions from effluents. Owing to abundant adsorptive sites, the MCC-PDA-PEI/CS-PDA-PEI hydrogel showed excellent Cu²⁺, Zn²⁺, and Ni²⁺ adsorbabilities of ~434.8, ~277.7, and ~261.8 mg/g, respectively, in a single-ion adsorption system with the adsorption kinetics and isotherm complied with pseudo-second-order and Langmuir models, respectively. In a multi-ion adsorption system, hydrogel removes mixed metal cations with slightly higher selectivity for Cu²⁺. In accordance with X-ray photoelectron and Fourier-transform-infrared spectrometric analyses, a plausible binding mechanism of metal cations on the as-prepared hydrogel was proposed by chelation between hydrogel functional groups and metal ions. In the repetitive adsorption/desorption experiments, the hydrogel retained >40% metal ion adsorption and desorption capacities after four cycles. Furthermore, the Cu²⁺-adsorbing hydrogel could serve as a support for the in situ development of Cu nanoparticles, which showed excellent catalytic performance as demonstrated by the transformation of 4-nitrophenol (4-NP) to 4-aminophenol. This work provides a novel ecofriendly, reusable, and highly-efficient adsorbent, as well as a biocatalyst for remediation of heavy metal cations and 4-NP polluted effluents.

Recent Advances in Adsorptive Nanocomposite Membranes for Heavy Metals Ion Removal from Contaminated Water: A Comprehensive Review

Water contamination is one of the most urgent concerns confronting the world today. Heavy metal poisoning of aquatic systems has piqued the interest of various researchers due to the high toxicity and carcinogenic consequences it has on living organisms. Due to their exceptional attributes such as strong reactivity, huge surface area, and outstanding mechanical properties, nanomaterials are being produced and employed in water treatment. In this review, recent advances in the use of nanomaterials in nanoadsorptive membrane systems for wastewater treatment and heavy metal removal are extensively discussed. These materials include carbon-based nanostructures, metal nanoparticles, metal oxide nanoparticles, nanocomposites, and layered double hydroxide-based compounds. Furthermore, the relevant properties of the nanostructures and the implications on their performance for water treatment and contamination removal are highlighted. The hydrophilicity, pore size, skin thickness, porosity, and surface roughness of these nanostructures can help the water permeability of the nanoadsorptive membrane. Other properties such as surface charge modification and mechanical strength can improve the metal adsorption effectiveness of nanoadsorptive membranes during wastewater treatment. Various nanocomposite membrane fabrication techniques are also reviewed. This study is important because it gives important information on the roles of nanomaterials and nanostructures in heavy metal removal and wastewater treatment.

GO-SWCNT Buckypapers as an Enhanced Technology for Water Decontamination from Lead

Water decontamination is an important challenge resulting from the incorrect disposal of heavy metal waste into the environment. Among the different available techniques (e.g., filtration, coagulation, precipitation, and ion-exchange), adsorption is considered the cheapest and most effective procedure for the removal of water pollutants. In the last years, several materials have been tested for the removal of heavy metals from water, including metal-organic frameworks (MOFs), single-walled carbon nanotubes (SWCNTs), and graphene oxide (GO). Nevertheless, their powder consistency, which makes the recovery and reuse after adsorption difficult, is the main drawback for these materials. More recently, SWCNT buckypapers (SWCNT BPs) have been proposed as self-standing porous membranes for filtration and adsorption processes. In this paper, the adsorption capacity and selectivity of Pb²⁺ (both from neat solutions and in the presence of other interferents) by SWCNT BPs were evaluated as a function of the increasing amount of GO used in their preparation (GO-SWCNT buckypapers). The highest adsorption capacity, 479 ± 25 mg g⁻¹, achieved for GO-SWCNT buckypapers with 75 wt.% of graphene oxide confirmed the effective application of such materials for cheap and fast water decontamination from lead.

Heavy metal removal by biomass-derived carbon nanotubes as a greener environmental remediation: A comprehensive review

The concentrations of heavy metal ions found in waterways near industrial zones are often exceed the prescribed limits, posing a continued danger to the environment and public health. Therefore, greater attention has been devoted into finding the efficient solutions for adsorbing heavy metal ions. This review paper focuses on the synthesis of carbon nanotubes (CNTs) from biomass and their application in the removal of heavy metals from aqueous solutions. Techniques to produce CNTs, benefits of modification with various functional groups to enhance sorption uptake, effects of operating parameters, and adsorption mechanisms are reviewed. Adsorption occurs via physical adsorption, electrostatic interaction, surface complexation, and interaction between functional groups and heavy metal ions. Moreover, factors such as pH level, CNTs dosage, duration, temperature, ionic strength, and surface property of adsorbents have been identified as the common factors influencing the adsorption of heavy metals. The oxygenated functional groups initially present on the surface of the modified CNTs are responsible towards the adsorption enhancement of commonly-encountered heavy metals such as Pb²⁺, Cu²⁺, Cd²⁺, Co²⁺, Zn²⁺, Ni²⁺, Hg²⁺, and Cr⁶⁺. Despite the recent advances in the application of CNTs in environmental clean-up and pollution treatment have been demonstrated, major obstacles of CNTs such as high synthesis cost, the agglomeration in the post-treated solutions and the secondary pollution from chemicals in the surface modification, should be critically addressed in the future studies for successful large-scale applications of CNTs.

Effective dispersion of oxidized multi-walled carbon nanotubes using a water-soluble N,O-carboxymethyl chitosan via non-covalent interaction

Dispersible multi-walled carbon nanotubes (MWCNTs) in water have been widely applied in the nanotechnology field. This study reports a water-soluble N,O-carboxymethyl chitosan(N,O-CMCS) assisted individual dispersion of oxidized multi-walled carbon nanotubes (oMWCNTs) as a dispersant. First, the dispersing agent N,O-CMCS was successfully synthesized using the nucleophilic substitution of deacetylated chitosan with chloroacetic acid in an alkaline solution. It was further confirmed using Fourier transform infrared spectroscopy (FTIR). Second, after the treatment with the concentrated hydrochloric acid, the prepared oMWCNTs were dispersed in an aqueous solution of N,O-CMCS under ultrasonic vibrations. Finally, the dispersed aqueous solution was subjected to centrifugation to collect the supernatant of individually dispersed N,O-CMCS/oMWCNTs. In addition, transmission electron microscopy (TEM) further confirmed that the purity of oMWCNTs was improved after the acidification progress. Besides, the stability of the dispersion solution was evidenced by digital photos of oMWCNTs dispersed by N,O-CMCS before and after. Moreover, the UV-vis spectrum (the characteristic peak of dispersed oMWCNTs downshifted 13 nm) showed that the supernatant was enriched by the individual oMWCNTs. In particular, the analytical results of FTIR (the –NH₂ band of N,O-CMCS downshifted 7 cm⁻¹), resonance Raman spectroscopy (the I_D/I_G ratio of dispersed oMWCNTs only increased 0.14), and XRD identified the formation of a non-convalent interaction between N,O-CMCS and oMWCNTs. These findings reveal the dispersing nature of N,O-CMCS towards oMWCNTs in water media.

The stability of a dispersion solution was evidenced by images of oMWCNTs-dispersed by N,O-CMCS before (b) and after (a). UV-vis further showed that individual oMWCNTs were enriched via the non-covalent interaction between oMWCNTs and N,O-CMCS.

Removal of Heavy Metals from Wastewater Using Novel Polydopamine-Modified CNTs-Based Composite Membranes

The presence of major heavy metals including Pb2+, Cu2+, Co2+, Ni2+, Hg2+, Cr6+, Cd2+, and Zn2+ in water is of great concern because they cannot degrade or be destroyed. They are toxic even at very low concentrations. Therefore, it is necessary to remove such toxicants from water. In the current study, polydopamine carbon nanotubes (PD-CNTs) and polysulfone (PS) composite membranes were prepared. The structural and morphological features of the prepared PDCN composite membranes were studied using FTIR, XRD, SEM, and EDS. The potential application of PDCNs for heavy metal removal was studied for the removal of Pb2+, Cr6+, and Cd2+ from wastewater. The maximum removal efficiency of 96.1% was obtained for Cr6+ at 2.6 pH using a composite membrane containing 1.0% PD-CNTs. The removal efficiencies decreased by 64.1 and 73.4, respectively, by enhancing the pressure from 0.50 up to 0.85 MPa. Under the same circumstances, the percentages of Pb+2 removal at 0.49 bar by the PDCNS membranes containing 0.5% and 1.0% PD-CNT were 70 and 90.3, respectively, and decreased to 54.3 and 57.0, respectively, upon increasing the pressure to 0.85 MPa. The results showed that PDCNS membranes have immense potential for the removal of heavy metals from water.

Recent Advances in Biopolymeric Membranes towards the Removal of Emerging Organic Pollutants from Water

Herein, this paper details a comprehensive review on the biopolymeric membrane applications in micropollutants' removal from wastewater. As such, the implications of utilising non-biodegradable membrane materials are outlined. In comparison, considerations on the concept of utilising nanostructured biodegradable polymeric membranes are also outlined. Such biodegradable polymers under considerations include biopolymers-derived cellulose and carrageenan. The advantages of these biopolymer materials include renewability, biocompatibility, biodegradability, and cost-effectiveness when compared to non-biodegradable polymers. The modifications of the biopolymeric membranes were also deliberated in detail. This included the utilisation of cellulose as matrix support for nanomaterials. Furthermore, attention towards the recent advances on using nanofillers towards the stabilisation and enhancement of biopolymeric membrane performances towards organic contaminants removal. It was noted that most of the biopolymeric membrane applications focused on organic dyes (methyl blue, Congo red, azo dyes), crude oil, hexane, and pharmaceutical chemicals such as tetracycline. However, more studies should be dedicated towards emerging pollutants such as micropollutants. The biopolymeric membrane performances such as rejection capabilities, fouling resistance, and water permeability properties were also outlined.