Removal of copper metal through a hybrid bio-chemical precipitation process / Nurul Fariha Lokman

Conventionally, heavy metals are being removed by chemical precipitation process using carbo nates and hydroxides. Sulphide is one of the alternatives anions added for chemical precipitation to precipitate out copper effectively, but at significantly high costs and not environmental friendly. The uniqueness of this study is sulphide being produced through a biological process using sulphate reducing bacteria (SRB) to precipitate heavy metal. The novelty of this study relics on the significance of using two separate reactors, namely the upflow anaerobic sludge blanket (UASB) reactor and precipitator reactor. The substrates including glucose and sodium sulphate are left under anaerobic condition in the UAS B reactor. While, the copper added as a substrate is left in the precipitator reactor. The SRB in the UASB reactor reduce sulphate to hydrogen sulphide gas. Then, the biologically produced hydrogen sulphide gas was used for copper precipitation in the precipitator reactor. The efficiencies of the process can be evaluated separately since these pro cesses take place in two different reactors. This research intends to quantify the amount of methane gas that can be produced in the UASB reactor under limited sulphate condition and to quantify the biological production of sulphide and hydrogen sulphide gas in the UASB reactor under excess sulphate condition. In addition, it is the aim of this study to evaluate the efficiency of copper metal removal through precipitation process using biologically produced sulphide. Results showed that 79.25% of methane can be recovered and very minimal sulphide was produced under condition of low sulphate concentration. However, when the sulphate concentration is high, only 14.42% of methane produced with increasing of 76% sulphide produced. Furthermore, the hydrogen sulphide gas remained in precipitator reactor was 66%. However, only 14% of sulphide has been used to precipitate copper with efficiency of 87% in the precipitator reactor. Therefore, this process has great potential to be adopted in industries to treat industrial wastewater with copper based problems

Highly sensitive SPR response of Au/chitosan/graphene oxide nanostructured thin films toward Pb (II) ions

Optical sensors based on surface plasmon resonance (SPR) are utilized for detecting toxic heavy metals in solutions. To improve the sensitivity of SPR sensors, nanostructured thin films with active layers can be synthesized. In this study, the response to Pb (II) was measured and compared for SPR sensors incorporating gold–chitosan–graphene oxide (Au/CS/GO) nanostructured thin films and Au/CS films. The characterization of Au/CS/GO using FESEM analysis revealed a film composed of nanosheets with wrinkled, rough surfaces. The results from XRD analysis confirmed the successful incorporation of GO in the prepared films. Additionally, AFM analysis determined that the Au/CS/GO films had a root mean square (rms) roughness of 28.38 nm and were considerably rougher than the Au/CS films. Upon exposure to a 5 ppm Pb (II) ion solution, the Au/CS/GO films exhibited higher SPR sensitivity, as much as 1.11200 ppm−1, than Au/CS films, 0.77600 ppm−1. This enhancement of the SPR response was attributed to strong covalent bonding between CS and GO in these films. These results indicated that the Au/CS/GO films show potential for the detection of heavy metal pollution in environmental applications

Sensitivity Enhancement of Pb(II) Ion Detection in Rivers Using SPR-Based Ag Metallic Layer Coated with Chitosan–Graphene Oxide Nanocomposite

The detection of Pb(II) ions in a river using the surface plasmon resonance (SPR)-based silver (Ag) thin film technique was successfully developed. Chitosan–graphene oxide (CS-GO) was coated on top of the Ag thin film surface and acted as the active sensing layer for Pb(II) ion detection. CS-GO was synthesized and characterized, and the physicochemical properties of this material were studied prior to integration with the SPR. In X-ray photoelectron spectroscopy (XPS), the appearance of the C=O, C–O, and O–H functional groups at 531.2 eV and 532.5 eV, respectively, confirms the success of CS-GO nanocomposite synthesis. A higher surface roughness of 31.04 nm was observed under atomic force microscopy (AFM) analysis for Ag/CS-GO thin film. The enhancement in thin film roughness indicates that more adsorption sites are available for Pb(II) ion binding. The SPR performance shows a good sensor sensitivity for Ag/CS-GO with 1.38° ppm−1 ranging from 0.01 to 5.00 ppm of standard Pb(II) solutions. At lower concentrations, a better detection accuracy was shown by SPR using Ag/CS-GO thin film compared to Ag/CS thin film. The SPR performance using Ag/CS-GO thin film was further evaluated with real water samples collected from rivers. The results are in agreement with those of standard Pb(II) ion solution, which were obtained at incidence angles of 80.00° and 81.11° for local and foreign rivers, respectively