Textile wastewater heavy metal pollution has become a severe environmental problem worldwide. Metal ion inclusion in a dye molecule exhibits a bathochromic shift producing deeper but duller shades, which provides excellent colouration. The ejection of a massive volume of wastewater containing heavy metal ions such as Cr (VI), Pb (II), Cd (II) and Zn (II) and metal-containing dyes are an unavoidable consequence because the textile industry consumes large quantities of water and all these chemicals cannot be combined entirely with fibres during the dyeing process. These high concentrations of chemicals in effluents interfere with the natural water resources, cause severe toxicological implications on the environment with a dramatic impact on human health. This article reviewed the various metal-containing dye types and their heavy metal ions pollution from entryway to the wastewater, which then briefly explored the effects on human health and the environment. Graphene-based absorbers, specially graphene oxide (GO) benefits from an ordered structured, high specific surface area, and flexible surface functionalization options, which are indispensable to realize a high performance of heavy metal ion removal. These exceptional adsorption properties of graphene-based materials support a position of ubiquity in our everyday lives. The collective representation of the textile wastewater's effective remediation methods is discussed and focused on the GO-based adsorption methods. Understanding the critical impact regarding the GO-based materials established adsorption portfolio for heavy metal ions removal are also discussed. Various heavy-metal ions and their pollutant effect, ways to remove such heavy metal ions and role of graphene-based adsorbent including their demand, perspective, limitation, and relative scopes are discussed elaborately in the review.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/tcr.202000153

A Review on Heavy Metal Ions and Containing Dyes Removal Through Graphene Oxide-Based Adsorption Strategies for Textile Wastewater Treatment

Recent advances on composite hydrogels designed for the remediation of dye-contaminated water and wastewater: A review

Neurotransmitters are endogenous chemical messengers which play an important role in many of the brain functions, abnormal levels being correlated with physical, psychotic and neurodegenerative diseases such as Alzheimer’s, Parkinson’s, and Huntington’s disease. Therefore, their sensitive and robust detection is of great clinical significance. Electrochemical methods have been intensively used in the last decades for neurotransmitter detection, outclassing more complicated analytical techniques such as conventional spectrophotometry, chromatography, fluorescence, flow injection, and capillary electrophoresis. In this manuscript, the most successful and promising electrochemical enzyme-free and enzymatic sensors for neurotransmitter detection are reviewed. Focusing on the activity of worldwide researchers mainly during the last ten years (2010–2019), without pretending to be exhaustive, we present an overview of the progress made in sensing strategies during this time. Particular emphasis is placed on nanostructured-based sensors, which show a substantial improvement of the analytical performances. This review also examines the progress made in biosensors for neurotransmitter measurements in vitro, in vivo and ex vivo.

https://www.mdpi.com/1424-8220/19/9/2037/pdf

Latest Trends in Electrochemical Sensors for Neurotransmitters: A Review.

The present work demonstrated the removal of hexavalent chromium from aqueous solutions on synthesized graphene oxide (GO) from graphite. The prepared GO was characterized by various analytical techniques such as X-ray diffraction, scanning electron micrograph, Fourier transformed infrared and zero point change. The entire metal adsorption study was conducted through batch mode with keeping constant stirring rate (150 rpm). The operating variables such as pH (2–8), contact time (1–60 min), adsorbent dose (0.005 g–0.01 g L−1) and initial concentration (5–80 µg L−1) were considered, and optimized variables were fixed at maximum percentage of removal. The studied results ascertained that the maximum removal (92.8%) was achieved at acidic pH(4). The equilibrium of Cr(VI) adsorption data was nicely fitted with Langmuir model with maximum adsorption capacity (qm) 1.222 µg g−1. The sorption kinetics was nicely explained with pseudo-first-order and intraparticle diffusion mechanism. Thermodynamics of Cr(VI) adsorption revealed that the adsorption was spontaneous, endothermic and entropy-driven process. Therefore, it is concluded that graphene oxide could be an effective and efficient alternative toward removal of Cr(VI) from aqueous solution.

/pdf/adsorption-of-cr-vi-from-aqueous-solution-on-graphene-oxide-1hj4vtvlkk.pdf

Adsorption of Cr(VI) from aqueous solution on graphene oxide (GO) prepared from graphite: equilibrium, kinetic and thermodynamic studies

Synthesis and characterization of arginine-doped polyaniline/walnut shell hybrid composite with superior clean-up ability for chromium (VI) from aqueous media: Equilibrium, reusability and process optimization

Facile synthesis of nitrogen-doped graphene aerogels for electrochemical detection of dopamine

Facile Assembly of Polyaniline/Graphene Oxide Composite Hydrogels as Adsorbent for Cr(VI) Removal

The alginate/reduced graphene oxide composite hydrogels with hierarchical network structures were synthesized through the hydrothermal treatment of graphene oxide and alginate in an aqueous solution followed by ionically cross-linking of metal ions. The network of reduced graphene oxide was prepared via self-assembly of graphene nanosheets in the presence of alginate during the hydrothermal process; then, the polymer network of alginate was obtained by ionically cross-linking, forming the composite hydrogel. The effect of metal ions on the physical properties of the composite hydrogels was investigated. The prepared alginate/reduced graphene oxide composite hydrogel cross-linked by Fe3+ ions showed higher compression strength and lower swelling ratio. Moreover, due to the synergetic interaction between graphene and alginate, the composite hydrogels exhibited the improved dye adsorption performance, especially for cationic dyes. Even after ten adsorption/desorption cycles, the composite hydrogels can retain more than 90% dye adsorption capacity. The results indicated that the composite hydrogel with good stability, adsorption and regeneration ability could be a promising candidate for dye removal from waste aqueous solutions.

Strong alginate/reduced graphene oxide composite hydrogels with enhanced dye adsorption performance

https://iopscience.iop.org/article/10.1088/2053-1591/ab1a85/pdf

Polypyrrole wrapped graphene/TiO 2 composites hydrogels for high performance supercapacitors

Three-dimensional porous sponge with good mechanical strength, high absorption capacity and recyclability is of scientific and technological interest. In this work, graphene oxide has been incorporated into poly(vinyl alcohol)–chitosan sponge during acetalization reaction of poly(vinyl alcohol) for the fabrication of macroporous and amphiphilic sponges. Mercury intrusion porosimetry and scanning electron microscopy indicate that the as-prepared sponges have interconnected open-cell structures. The incorporation of graphene oxide and the interconnected macroporous structures in the amphiphilic sponges endow them with improved absorption capacity for both water and organic liquids. Moreover, the absorbed liquids can be effectively collected through simple squeezing and the sponges can be used repeatedly while maintaining a relative high absorption capacity. The simple fabrication and improved performance of the resulting sponges suggest that they have potential industrial applications.

Lai Wei

Papers

Facile synthesis of nitrogen-doped graphene aerogels for electrochemical detection of dopamine

Facile Assembly of Polyaniline/Graphene Oxide Composite Hydrogels as Adsorbent for Cr(VI) Removal

Strong alginate/reduced graphene oxide composite hydrogels with enhanced dye adsorption performance

Polypyrrole wrapped graphene/TiO 2 composites hydrogels for high performance supercapacitors

High-performance poly(vinyl alcohol)–chitosan sponge modified with graphene oxide