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Detection and quantification of heavy metals in soil samples are significant in terms of environmental monitoring and risk assessment for metals. In order to improve the accuracy and precision to detect heavy metal, in this study, four standard samples (NASS-4, NASS-5, NASS-9, and NASS-16) were analyzed by evolving heating (electric heating plate, water bath, and microwave) and acidic systems (includes HCl, HNO3, HF, and HClO4). The result shows that different pretreatment methods have different effects on the extraction of heavy metal elements and five heavy metal elements (Cu, Zn, Pb, Ni, and Cr) were selected for optimization through pretreatment methods. Although the contents of heavy metals were same but we found diversity in the results. Under optimal conditions, the selected standard samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS), inductively coupled plasma atomic emission spectroscopy (ICP-AES), and atomic absorption spectroscopy (AAS), and the results were compared. The results show that different elements have their own most suitable detection methods, such as for Pb, the most suitable method is ICP-MS; and for Zn, the most suitable method is AAS. Pretreatment methods and detection techniques are combined to find and improve accuracy of results for certain elements. This study provides a reliable detection method for the accurate detection of heavy metals in the environment.

In this paper, a novel PP nanocomposites containing graphene/SiO2 hybrid (GOS) was fabricated via melt blending. It showed that GO has been chemically functionalized by selective monomers. Due to the existence of “heterogeneous nucleation effect”, the melting temperatures and thermal properties were improved, as verified by thermal analysis. GOS has been dispersed uniformly in the PP matrix due to the “barrier effects” between SiO2 and graphene sheets. Tensile tests showed that GOS filler provided substantially greater mechanical property enhancement when embedded into PP matrix. When the GOS filler loading was 0.25 wt.%, the tensile and impact strength of PP nanocomposite increased by 13.8% and 41% compared with those of pure PP and by 27.95% and 43.87% respectively, compared with those of PP nanocomposites that filled with GO alone, indicating that the combination of graphene and nano-SiO2 demonstrated a synergistic effect for the property enhancement of PP.

Chemically covalent bonded graphene oxide (MGO)/Poly(3-hydroxybutyrate) (PHB) nanocomposites were fabricated successfully through solution blending. Morphological observations indicated that MGO was dispersed well in the nanocomposites during solution intercalation. The mechanical and thermal property characterizations indicated that incorporation of 2.0 wt.% MGO resulted in the increasing of up to 101% and 46% in tensile strength and tensile modulus of nanocomposites, respectively, compared to neat PHB; while the maximum thermal decomposition temperature improved about 15.5 °C higher than that of PHB. Differential scanning calorimetric (DSC) analysis showed that the crystallization process of PHB accelerated, resulting in an increasing in crystallinity with the incorporation of MGO due to its’ “ nucleating effect”. Electrical conductivity analysis indicated that the electrical conductivity of MGO/PHB nanocomposites has increased by 14 orders in comparison to that of pure PHB, especially for r-MGO filled PHB nanocomposites (4 wt.% r-MGO loading). It was concluded that the formation of graphene-graphene network structure in the nanocomposites, the increases in homogeneous dispersion of graphene and interfacial interactions contributed to the enhancements of properties.

Reducing and chemically functional modification of graphene oxide (GO) has attracted much attention in nanomaterial fields due to the outstanding properties of the graphene. In this article, water, a low cost and environmentally friendly reduction agent, to reduce selectively GO to form reduced GO (rGO) was applied, followed by modifying rGO with functional monomer octadecylamine (ODA), and subsequently polypropylene (PP) based nanocomposites containing functional graphene were fabricated via masterbatch-melt blending technique. The effects of reduction and functionalization on the microstructural and chemical–physical properties of GO were investigated comparatively by using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS). The dispersibility of functional graphene before and after reduction was verified by using various agents. The experimental results showed that GO has been reduced selectively by water. Functional monomer ODA has been grated successfully on the surface of rGO and GO. The prepared graphene/PP nanocomposites were characterized by using Differential scanning calorimetric (DSC), XRD, scanning electron microscope (SEM), tensile, and impact tests. The results showed that the crystallization temperature (Tc) and melting temperature (Tm) of PP in the nanocomposites increased when the functional graphene was incorporated. The functional graphene has been dispersed uniformly in the PP matrix. Tensile tests showed that rG-ODA could improve the tensile strength and elastic modulus of composites more effectively than G-ODA. But G-ODA was more effectively in improving the toughness of PP than rG-ODA, as indicated by impact tests. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

To achieve dramatic improvements in the performance of natural rubber (NR), the graphite oxide nanosheets (GON)-reinforced NR nanocomposites have been prepared through solution mixing on the basis of pretreatment of graphite. The mechanical and thermal properties of GON/NR nanocomposites were characterized in contrast to the carbon black (CB)/NR nanocomposite. The mechanical properties of the GON-reinforced NR showed a considerable increase compared to the neat NR and traditional CB/NR nanocomposite. The initial modulus of pure NR was increased for up to 53.6% when 7 wt% GON is incorporated. The modulus and strength of NR with GON appear to be superior to those of CB with the same filler content. The dispersion state of the nanofillers into NR was investigated by scanning electron microscopy and X-ray diffraction, and the results indicated that nanofillers have been dispersed homogeneously in the NR matrix. Fourier transform infrared spectra showed possible interfacial interactions between fillers and NR matrix. Differential scanning calorimetry and thermogravimetric analysis showed that the Tg and thermal decomposition temperature of NR slightly increased with the addition of the fillers, especially for that of GON/NR nanocomposites. According to this study, application of the physical and mechanical properties of GON to NR can result in rubber products which have improved mechanical, physical, and thermal properties, compared with existing NR products reinforced with CB. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

In this paper, the surface hydroxylation modification of nano-alumina (nano-Al2O3) to result nano-Al2O3–OH and the chemical modification of graphene oxide (GO) by using silane coupling agent to produce GO-KH560 were first carried out respectively, followed by solution compounding to synthesis a novel three-dimensional functional hybrid filler (nano-Al2O3–OH/GO-KH560), and then polyamide 6 (PA6)/nano-Al2O3–OH/GO-KH560 (abbreviated as P-A-OH-G-KH560) thermally conductive nanocomposites were fabricated by melt blending technique and investigated for its morphological, mechanical and thermal properties. Morphological characterization revealed better dispersion of nano-Al2O3 and GO in the PA6 nanocomposites, which is attributed to the improved interfacial interaction between the PA6 and hybrid fillers. Loading of the hybrid fillers in the PA6 nanocomposites resulted in the significant improvement in mechanical properties such as tensile strength and elastic modulus and this effect is more pronounced on the increasing the hybrid fillers loading amount, when compared to the PA6 and pristine nano-Al2O3 filled system. Differential scanning calorimetric analysis showed that the crystallization of the PA6 nanocomposites was improved. The thermal conductivity of the P-A-OH-G-KH560 (100/5/0.8) nanocomposite increased by 86.13% compared with that of pure PA6. In summary, PA6 nanocomposites with fairly good mechanical and thermal conductivity are obtained at low filler contents.

To improve the physical properties of poly(butylenes terephthalate) (PBT), a series of nanocomposites based on PBT and microwave exfoliated graphite oxide nanosheets (MEGONSs) are prepared via melt compounding technique, and their structures, thermal stabilities, mechanical, rheological and electrical properties are reported. Scanning electron microscope and X-ray diffraction exhibit that graphene platelets of MEGONS are well dispersed and exfoliated in the PBT matrix even at high MEGONS content of 4.0 wt.%. DSC cooling and following heating thermograms of the nanocomposites demonstrate that graphene platelets of MEGONS play a role as effective nucleating agents for PBT a-phase crystals and thus lead to accelerating the overall crystallization of the nanocomposites. Thermal stability of PBT/MEGONS nanocomposites improved substantially due to the gas barrier effect of graphene platelets of MEGONS dispersed in the PBT matrix. The rheological analysis shows the low frequency plateau of shear modulus and the shear thinning behavior of the nanocomposites. The mechanical modulus of the nanocomposites enhanced significantly with increasing MEGONS content. The electrical conductivity test shows a pronounced increase in electrical conductivity from an insulator to almost a semiconductor with increasing MEGONS content. The electrical percolation threshold of the nanocomposites is found to be formed at the MEGONS concentration between 1.0 and 2.0 wt.%.

Different formulations of microwave-exfoliated graphite oxide (MEGO) based thermoplastic polyurethane (TPU) nanocomposites were successfully prepared via melt blending followed by injection molding. The spectroscopic study indicated that a strong interfacial interaction had developed between the MEGO and the TPU matrix. The microscopic observations showed that the MEGO layers were homogeneously dispersed throughout the TPU matrix. Thermal analysis indicated that the glass transition temperatures ( T g ) of the nanocomposites increased with increasing MEGO content and their thermal stability improved in comparison with pure TPU matrix. The mechanical properties of nanocomposites improved substantially by the incorporation of MEGO into the TPU matrix. Electrical conductivity test indicated that a conductivity of 10 −4 S cm −1 was achieved in the nanocomposite containing only 4.0 wt.% of MEGO.