Graphene has attracted multidisciplinary study because of its unique physicochemical properties. Herein, few-layered graphene oxide nanosheets were synthesized from graphite using the modified Hummers method, and were used as sorbents for the removal of Cd(II) and Co(II) ions from large volumes of aqueous solutions. The effects of pH, ionic strength, and humic acid on Cd(II) and Co(II) sorption were investigated. The results indicated that Cd(II) and Co(II) sorption on graphene oxide nanosheets was strongly dependent on pH and weakly dependent on ionic strength. The abundant oxygen-containing functional groups on the surfaces of graphene oxide nanosheets played an important role on Cd(II) and Co(II) sorption. The presence of humic acid reduced Cd(II) and Co(II) sorption on graphene oxide nanosheets at pH < 8. The maximum sorption capacities (Csmax) of Cd(II) and Co(II) on graphene oxide nanosheets at pH 6.0 ± 0.1 and T = 303 K were about 106.3 and 68.2 mg/g, respectively, higher than any currently reporte...

Few-Layered Graphene Oxide Nanosheets As Superior Sorbents for Heavy Metal Ion Pollution Management

Worldwide regulatory frameworks for the assessment and remediation of contaminated soils have moved towards a risk-based approach, taking contaminant bioavailability into consideration. However, there is much debate on the precise definition of bioavailability and on the standardization of methods for the measurement of bioavailability so that it can be reliably applied as a tool for risk assessment. Therefore, in this paper, we reviewed the existing definitions of heavy metal bioavailability in relation to plant uptake (phytoavailability), in order to better understand both the conceptual and operational aspects of bioavailability. The related concepts of specific and non-specific adsorption, as well as complex formation and organic ligand affinity were also intensively discussed to explain the variations of heavy metal solubility and mobility in soils. Further, the most frequently used methods to measure bioavailable metal soil fractions based on both chemical extractions and mechanistic geochemical models were reviewed. For relatively highly mobile metals (Cd, Ni, and Zn), a neutral salt solution such as 0.01 M CaCl2 or 1 M NH4NO3 was recommended, whereas a strong acid or chelating solution such as 0.43 M HNO3 or 0.05 M DTPA was recommended for strongly soil-adsorbed and less mobile metals (Cu, Cr, and Pb). While methods which assessed the free metal ion activity in the pore water such as DGT and DMT or WHAM/Model VI, NICA-Donnan model, and TBLM are advantageous for providing a more direct measure of bioavailability, few of these models have to date been properly validated.

Bioavailability of heavy metals in soils: definitions and practical implementation—a critical review

Removal of cobalt ions from aqueous solution by an amination graphene oxide nanocomposite

Salinity increases the mobility of Cd, Cu, Mn, and Pb in the sediments of Yangtze Estuary: Relative role of sediments’ properties and metal speciation

The chemical affinity of graphene oxide (GO) nanosheets with radionuclides (Eu(III) and U(VI)) was determined by macroscopic, spectroscopic and modeling techniques The macroscopic results showed that the adsorption of Eu(III) and U(VI) on GO nanosheets was independent of ionic strength, indicating that inner-sphere surface complexation predominated their adsorption The maximum adsorption capacities calculated from a Langmuir model at pH 40 and T = 303 K were 20833 mg U(VI) and 2870 mg Eu(III) per gram of GO nanosheets, respectively No hysteresis was observed for both Eu(III) and U(VI) on GO nanosheets when desorption was initiated by lowering solution pH While desorption was induced by replacing the radionuclide supernatant liquid with radionuclide-free electrolyte solution, the adsorption–desorption hysteresis was observed for U(VI) but not for Eu(III), indicating that the chemical affinity of GO nanosheets with U(VI) was stronger than that of GO nanosheets with Eu(III) The adsorption behaviors of Eu(III) and U(VI) on GO nanosheets can be fitted by a double diffuse layer surface complexation model with the mononuclear monodentate >SOM(n−1)+ and >SOMOH(n−2)+ complexes, and larger log K values of U(VI) was observed as compared to those of Eu(III) According to the spectroscopic analysis, the irreversible adsorption of U(VI) on GO nanosheets at variable radionuclide concentrations was attributed to the oxygen-containing functional groups

/pdf/determination-of-chemical-affinity-of-graphene-oxide-1a1pev95bs.pdf

Determination of chemical affinity of graphene oxide nanosheets with radionuclides investigated by macroscopic, spectroscopic and modeling techniques.

https://bibliotecadigital.ipb.pt/bitstream/10198/6766/1/Mobility_Geoderma_2011.pdf

Mobility of Cr, Pb, Cd, Cu and Zn in a loamy sand soil: a comparative study

/pdf/evaluation-and-kinetic-study-of-alkaline-ionic-liquid-for-2n3g4mkf.pdf

Evaluation and kinetic study of alkaline ionic liquid for biodiesel production through transesterification of sunflower oil

Renewable biomass fuels are gaining attention as a cleaner energy alternative to fossil-based resources. Biodiesel, derived from biological sources, is particularly attractive due to its renewable and ecological benefits. Researchers are actively exploring various methodologies to convert biomass into gaseous and liquid fuels, similar to petroleum products. To optimize production and accommodate different feedstock sources, biodiesel production through different routes is becoming popular. The purification of biodiesel is an important step, and current methods involving water usage are being replaced with more sustainable alternatives. Adsorption and ion exchange, known as dry washing methods, are widely used for biodiesel purification worldwide. These processes use an adsorbent to selectively remove impurities from the liquid phase, offering advantages such as easy integration, shorter purification time, reduced water consumption, and minimal effluent generation. This review focuses on biodiesel production and purification methods, highlighting the advantages of adsorption over traditional wet washing methods. 

Review of biodiesel production using various feedstocks and its purification through several methodologies, with a specific emphasis on dry washing

https://repositorium.sdum.uminho.pt/bitstream/1822/17000/1/3546.pdf

Bioleaching of hexavalent chromium from soils using Acidithiobacillus thiooxidans

Adsorption is a treatment process based on accumulation of the adsorbate (pollutant) on the adsorbent surface that has been successful used for the optimization of wastewater treatment plant effluents cleaning. This work will present the main experimental results for the removal of naproxen from water by adsorption using activated carbon obtained from olive stones. Four types of activated carbon material were prepared from olive stones. The batch method was applied to experimentally measure the equilibrium adsorption isotherms. The most significant adsorption parameters were optimized, such as the solution pH, mass of the adsorbent, contact time and temperature. The physicochemical characterization of the pyrolyzed material shows a considerable superficial area of 608 m2/g when compared with other natural biomass-based materials. A removal efficiency of 100% was obtained for 24 h and a pH=4.5. The Langmuir model was used to better describe the adsorption behavior for adsorbent with better removal performance with the highest maximum adsorption capacity value of 35.2 mg naproxen/g adsorbent. The kinetics of the adsorption is well described by a pseudo-second order model. Obtained results in this work clearly show that olive stones, usually a residue from the Portuguese and Mediterranean oliviculture, can be exploited as a promising and lowcost biomass source on the production of adsorbent materials with considerable potential to remove micropollutants, such as the naproxen, from water.

Valorization of oliviculture residues to produce biochars for the removal of naproxen from water

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