Environmental sustainability has gained acceptance to achieving the goal of a secure ecosystem with a reliable management system. Heavy metal remediation of aqueous streams is of special concern due to the intractability and persistence in the environment. Adsorption is a potential alternative to the existing inefficient conventional technologies for the removal and recovery of metal ions from aqueous solutions and becomes vital to align with the Sustainable Development Goals (SDGs) and mitigate the adverse environmental and social impacts. Calcium Alginate-Graphene oxide (CA-GO) composite has been synthesized for the adsorption of heavy metals including Cr3+, Cu2+, and Cd2+ ions from tannery effluents. Graphene oxide is prepared from commercial graphite powder and reacted with sodium alginate and calcium chloride to form the beads of CA-GO composite. The developed composite was characterized by FTIR, elemental analysis, SEM, XRD analysis, and Raman spectroscopy. Moreover, the effect of pH, adsorbent dosage, contact time, and initial concentration of metal ions on the adsorption capacity were investigated through batch experiments. At a pH>3.0 (pHzpc), the carboxyl group of CA-GO was deprotonated to make the surface negatively charged and facilitate metal adsorption. The optimum pH and maximum adsorption capacity of CA-GO for removal of Cr(III), Cu(II), and Cd(II) were 4.5, 6.0, and 7.0, and 90.58, 108.57, and 134.77 mg g-1, respectively. The kinetics, adsorption isotherms, and thermodynamics were studied to determine the adsorption mechanism. The kinetic of adsorption adopted the second-order model. Thermodynamic parameter were calculated and the adsorption process was determined to be exothermic and spontaneous at room temperature. The developed composite has been efficaciously applied for the removal of metal ions and pollution from real tannery effluents.

Hydroxyapatite (HAp) coatings currently have limited therapeutic applications because they lack anti-infection, osteoinductivity, and poor mechanical characteristics. On the titanium substrate, electrochemical deposition (ECD) was used to construct the strontium (Sr)-featuring hydroxyapatite (HAp)/graphene oxides (GO)/linezolid (LZ) nanomaterial coated with antibacterial and drug delivery properties. The newly fabricated nanomaterials were confirmed by X-ray diffraction analysis (XRD), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis and morphological features were examined by scanning electron microscope (SEM) analysis. The results reveal multiple nucleation sites for SrHAp/GO/LZ composite coatings due to oxygen-comprising moieties on the 2D surface of GO. It was shown to be favorable for osteoblast proliferation and differentiation. The elastic modulus and hardness of LZ nanocomposite with SrHAp/GO/LZ coatings were increased by 67 % and 121 %, respectively. An initial 5 h burst of LZ release from the SrHAp/GO/LZ coating was followed by 14 h of gradual release, owing to LZ\'s physical and chemical adsorption. The SrHAp/GO/LZ coating effectively inhibited both S. epidermidis and S. aureus, and the inhibition lasted for three days, as demonstrated by the inhibition zone and colony count assays. When MG-63 cells are coated with SrHAp/GO/LZ composite coating, their adhesion, proliferation, and differentiation greatly improve when coated with pure titanium. A novel surface engineering nanomaterial for treating and preventing osteoporotic bone defects, SrHAp/GO/LZ, was shown to have high mechanical characteristics, superior antibacterial abilities, and osteoinductivity.

This article investigated the kinetic studies of thorium adsorption from an aqueous solution with graphene oxide functionalized with aminomethyl phosphonic acid (AMPA) as an adsorbent. First, the AMPA-GO adsorbent was characterized using TEM, XRD, and FTIR methods. Experiments were performed in two batch and continuous modes. In batch mode, adsorption kinetics were studied in different pH (1-4), temperature (298-328 K), initial concentration (50-500 mg L-1), and dosages (0.1-2 g L-1). The results showed that thorium adsorption kinetic follows pseudo-first-order kinetic model and that the adsorption reaction is endothermic. The maximum experimental adsorption capacity of thorium ions was observed 138.84 mg g-1 at a pH of 3, adsorbent dosage of 0.5 g L-1, and a temperature of 328 K. The results showed that AMPA-GO adsorbent can be used seven times with an acceptable change in adsorption capacity. In continuous conditions, the effect of feed flow rate (2-8 mL min-1), initial concentration (50-500 mg L-1), and column bed height (2-8 cm) was investigated. The continuous data was analyzed using the Thomas, Yoon-Nelson, and Bohart-Adams models. The experimental data of the column were well matched with the Thomas, and Yoon-Nelson models. The research results showed that the use of functionalized graphene oxide adsorbents has a great ability to remove thorium from aqueous solutions.

The aim of this study was to obtain three experimental resin-based cements containing GO and HA-Ag for posterior restorations. The samples (S0, S1, and S2) shared the same polymer matrix (BisGMA, TEGDMA) and powder mixture (bioglass (La2O3 and Sr-Zr), quartz, GO, and HA-Ag), with different percentages of graphene oxide (0%, 0.1%, 0.2% GO) and silver-doped hydroxyapatite (10%, 9.9%, 9.8% HA-Ag). The physical-chemical properties (water absorption, degree of conversion), mechanical properties (DTS, CS, FS), structural properties (SEM, AFM), and antibacterial properties (Staphylococcus aureus, Enterococcus faecalis, Streptococcus mutans, Porphyromonas gingivalis, and Escherichia coli) were investigated. The results showed that the mechanical properties, except for the diametral tensile test, increased with the rise in the %GO. After 28 days, water absorption increased with the rise in the %GO. The surface structure of the samples did not show major changes after water absorption for 28 days. The antibacterial effects varied depending on the samples and bacterial strains tested. After increasing the %GO and decreasing the %HA-Ag, we observed a more pronounced antibacterial effect. The presence of GO, even in very small percentages, improved the properties of the tested experimental cements.

In this work, the electrochemical synthesis of PANI and GO-modified PANI was performed using cyclic voltammetry, varying the amount of GO, 1 mg (PG1), 5 mg (PG5), and 10 mg (PG10) to analyze the effect of the amount of GO on the composite. PANI, PG1, PG5, and PG10 materials were characterized using optical microscopy, SEM, UV-vis, FTIR, Raman, and wettability. A stability test was also carried out by putting the materials to 500 oxidation-reduction cycles using cyclic voltammetry. The synthesis method allowed GO in PANI to be added through a chemical interaction between the two compounds. It was also found that the addition of GO led to an improvement in the hydrophilic character of the composite, which would lead to an improvement in the diffusion of reagents/species when the composites are used in aqueous media processes. The results of the stability test showed that the PG10 material presented a lower % loss of specific capacitance and energy compared with the other materials, which indicates that the GO presence (in the amount specified) improves the stability of the PANI. The PG10 material showed favorable and promising conditions for its use in fuel cell and battery processes.

Efficient recovery of gallium (Ga) from vanadium slag processing residue (VSPR) solution is of great significance for environmental protection and resource utilization, but improving its selective adsorption against the coexisting Sc3+ and In3+ is still challenging. Herein, a novel adsorbent consisting of 4-amino-3-hydrazino-1,2,4-triazol-5-thiol (AHTZT)-modified graphene oxide (GO-AHTZT) was successfully synthesized that exhibits a higher adsorption selectivity for Ga3+ in VSPR solution with coexisting Sc3+ and In3+. Under optimal conditions, the adsorption capacity of GO-AHTZT for Ga3+ can reach 23.92 mg g-1, which is 4.9 and 12.6 times higher than that for Sc3+ (4.87 mg g-1) and In3+ (1.90 mg g-1) adsorption, indicating the excellent anti-interference ability of GO-AHTZT against Sc3+ and In3+. The process and mechanism of Ga3+ adsorption onto GO-AHTZT was also studied and discussed in detail. By measuring the adsorption process and by characterizing the adsorbent before and after adsorption, we demonstrate that the selective interaction between the Ga3+- and N-containing groups in AHTZT is the main reason for the improved adsorption selectivity. This work opens up an avenue for the design and synthesis of highly selective adsorbents for Ga3+ in complex VSPR solutions.

Graphene oxide (GO) is considered as a promising adsorbent material for the removal of metal from aqueous environments. Here, we have used the density functional theory (DFT) approach and a combination of parameters to characterise the interactions of GO with lead (Pb) and cadmium (Cd), i.e., typical harmful metals often found in water. Our model systems consist of a singly and doubly adsorbed neutral (Pb0, Cd0) and charged (Pb2+, Cd2+) atoms adsorbed on the GO nanoparticle of the chemical formula C30H14O15. We show that a single charged metal ion binds more strongly than a neutral atom of the same type. Moreover, to determine the possibility of multiple adsorptions of the GO nanoparticle, two metal atoms of the same species were co-adsorbed on its surface. We found a site-dependent adsorption energy such that when two atoms of the same specie are adsorbed at sites Si and Sj, the binding energy per atom depends on whether one of the two atoms is adsorbed firstly on the Si or Sj sites. Furthermore, the binding energy per atom for the two co-adsorbed atoms of the same specie (i.e., neutral or charged) is less than the binding energy of a singly adsorbed atom. This suggests that atoms may become less likely to be adsorbed on the GO nanoparticle when their concentration increases. We adduce the origin of this observation to be interplay between the metal-metal interaction on the one hand and GO-metal on the other, with the former resulting in less binding for the charged adsorbed metals in particular, due to repulsive interaction between two positively charged ions. The frontier molecular orbitals analysis and the calculated global reactivity descriptors of the respective GO-metal complexes revealed that all the GO-metal complexes have a smaller HOMO-LUMO gap (HLG) relative to that of pristine metal-free GO nanoparticle. This may indicate that although the GO-metal complexes are stable, they are less stable compared to metal-free GO nanoparticles. The negative values of the chemical potentials obtained for all the GO-metal complexes further confirm their stability. Our work differs from previous experimental studies in that those lacked details of the interaction mechanisms between GO, Pb and Cd, as well as previous theoretical studies which used limited numbers of parameters to characterise the GO-metal interactions. Rather, we present a set of parameters or descriptors which provide comprehensive physical and electronic characterisation of GO-metal systems as obtained via the DFT calculations. These parameters, along with those reported in previous studies, may find applications in rational design and high-throughput screening of graphene-based materials for water purification, as an example.

The antibacterial characteristics of graphene oxide (GO-SB) nano-sheets generated by charring sugarcane bagasse (SB) are described in this study. The antibacterial capability of GO-SB was improved when it was grafted with ethyl cellulose (EC) and polyvinyl alcohol (PVA) to form GO-SB/EC/PVA hydrogels. Characterization of GO-SB nanosheets and GO-SB/EC/PVA hydrogels was accomplished by using FTIR, SEM, XRD, and thermal studies. The antimicrobial activity was carried out against Gram positive bacteria [Micrococcus leutus & Staphylococcus aureus], Gram negative bacteria [Escherichia coli, Pseudomonas aeruginosa] and pathogenic fungal yeast [Candida albicans] applying the disc diffusion method. The disc diffusion method results showed that the improved GO-SB/EC/PVA exhibited a reasonable level of antimicrobial capability against Micrococcus leutus, demonstrating that the antimicrobial improvement of GO-SB was more effective in the GO-SB/EC/PVA hydrogels by increasing the inhibition zone of Gram-positive bacteria, Micrococcus leutus from (13.0 to 16.0 mm).

Many studies on flexible strain and pressure sensors have been reported due to growing interest in wearable devices for healthcare purposes. Here, we present flexible pressure and strain (motion) sensors prepared with only graphene oxide (GO) and commercial silk fabrics and yarns. The pressure sensors were fabricated by simply dipping the silk fabric into GO solution followed by applying a thermal treatment at 400 °C to obtain reduced GO (rGO). The pressure sensors were made from rGO-coated fabrics, which were stacked in three, five, and seven layers. A super-sensitivity of 2.58 × 103 kPa-1 at low pressure was observed in the seven-layer pressure sensor. The strain sensors were obtained from rGO-coated twisted silk yarns whose gauge factor was 0.307. Although this value is small or comparable to the values for other sensors, it is appropriate for motion sensing. The results of this study show a cost-effective and simple method for the fabrication of pressure and motion sensors with commercial silk and GO.

A special technique has been developed for producing a composite aerogel which consists of graphene oxide and soy wax (GO/wax). The reduction of graphene oxide was carried out by the stepwise heating of this aerogel to 250 °C. The aerogel obtained in the process of the stepwise thermal treatment of rGO/wax was studied by IR and Raman spectroscopy, scanning electron microscopy, and thermogravimetry. The heat treatment led to an increase in the wax fraction accompanied by an increase in the contact angle of the rGO/wax aerogel surface from 136.2 °C to 142.4 °C. The SEM analysis has shown that the spatial structure of the aerogel was formed by sheets of graphene oxide, while the wax formed rather large (200-1000 nm) clumps in the folds of graphene oxide sheets and small (several nm) deposits on the flat surface of the sheets. The sorption properties of the rGO/wax aerogel were studied with respect to eight solvent, oil, and petroleum products, and it was found that dichlorobenzene (85.8 g/g) and hexane (41.9 g/g) had the maximum and minimum sorption capacities, respectively. In the case of oil and petroleum products, the indicators were in the range of 52-63 g/g. The rGO/wax aerogel was found to be highly resistant to sorption-desorption cycles. The cyclic tests also revealed a swelling effect that occurred differently for different parts of the aerogel.