Abstract
As an environmental concern, the number of waste nitrile butadiene rubber (NBR) gloves that end up disposed of through landfills and incineration has increased tremendously. These methods of disposal are detrimental to environmental resources, as a result green environmentally friendly methods of disposal are of the utmost importance.
This thesis describes in detail the chemical recycling of waste nitrile butadiene rubber gloves. This project, therefore aimed to convert waste nitrile butadiene rubber gloves into activated carbon and pyrolytic oil. In the first part of the study, an analysis of the cost of gloves, usage of gloves per year (quantity), and disposal methods currently used at the University of Johannesburg, Department of Chemical Sciences was briefly discussed. In addition, the waste that is currently recycled at the University of Johannesburg is elaborate. Lastly, the sustainable integrated management program was described.
In the second part of the study, the first report describes the chemical recycling of waste nitrile butadiene rubber gloves into low-cost activated carbon absorbent and its application towards the adsorption of phenol pollutants in wastewater. The waste gloves were first converted to a char through pyrolysis, then activated using chemicals such as H3PO4, ZnCl2, KOH, and H2O2 to produce activated carbon. The produced activated carbon where then used as an adsorbent to remove phenol in wastewater. The structural morphology of synthesized activated carbon, (AC)-H3PO4, AC- ZnCl2, AC-KOH, and AC-H2O2 were characterized using Zeta potential, Fourier Transform Infrared Spectroscopy (FTIR), Elemental analyzer, Thermogravimetry analysis (TGA), Scanning Electron Microscopy (SEM), X-ray diffraction (XRD) and Brunauer-Emmette and Teller (BET). The zetapotential showed a negative isoelectric point for synthesized material. FTIR showed that there was a shift of the OH and CO2 vibrations to higher wavelength. Elemental analyzers revealed that the synthesis material composed more than 70 % of carbon. SEM showed that the synthesized activated carbon is of mesoporous and micropores type, while XRD revealed amorphous type of structure. TGA indicated that the synthesized material is stable at temperature lower than 800 ◦C. The highest phenol removal efficiency was achieved by H3PO4 with a removal efficiency of 76 % followed by ZnCl2 at 73
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%, KOH at 62 %, and H2O2 at 55 %. The results revealed that waste nitrile butadiene rubber gloves can be recycled into activated carbon adsorbent and utilized for the removal of phenol pollutants in wastewater.
The second report investigated the modification of AC-H3PO4 adsorbent to improve the removal efficiency of adsorbent towards phenol pollutants. The modification was conducted using ferrocene and sulfur to obtain AC-H3PO4/F7S8. The AC-H3PO4/Fe7S8 adsorbent was used to remove phenol in wastewater at the optimum experimental conditions of 0.3g, contact time of 120 min, pH of 4, and concentration of (10-50 mg/L), and the removal efficiency of 98 % was achieved. The results indicated that modification of activated carbon with ferrocene and sulphur enhanced the removal efficiency of phenol in wastewater.
The third report investigated the efficient removal of the modified activated carbon/ferrocene composite (AC-H3PO4/Fe7S8) adsorbent towards the removal of chromium (VI) and copper (II) in wastewater. The highest removal efficiency of 95,86 % for Cr (VI) and 81,14 % for Cu (II) was obtained at pH 6 and 7 respectively. The regeneration and reusability studies showed the highest removal efficiency when the HCl was used to regenerate spent AC-H3PO4/Fe7S8 adsorbent followed by the H2SO4 and HNO3 showing the least efficiency. Also, the results indicated that AC-H3PO4/Fe7S8 composite can be effectively used to remove heavy metals in wastewater treatment.
In the third part of the study, the waste nitrile butadiene rubber gloves were converted into pyrolytic oil through pyrolysis of the waste gloves. The characteristics of functional group composition present in the pyrolytic oil were qualitatively analyzed with the Fourier Transform Infrared Attenuated Total Reflectance Spectroscopy (FTIR-ATR). The results showed that the pyrolysis oil mainly contains alkane and alkene groups. The results show that the waste nitrile butadiene rubber gloves can be used as a precursor to produce pyrolytic oil.
Overall, the recycling protocol developed in this study provides a new way of recycling waste nitrile butadiene rubber gloves by converting them into low-cost, effective, readily available adsorbents that can be applied in removing pollutants in wastewater. Furthermore, the waste nitrile butadiene rubber gloves can be converted into low-cost fuel.