Preparation of Polylactic Acid/Nano-Composite Films with Oxidized Multi-Walled Carbon Nanotubes and Functionalized Graphene Oxide Nanoparticles for Organic Removal from Wastewater

  • Hiyam Hisham Haras Khalil

Student thesis: Master's Thesis

Abstract

The continued use of non-biodegradable polymeric-based membranes for water purification has led to an unsustainable accumulation of waste at disposal, resulting in various environmental problems. In this study, eco-friendly asymmetric ultrafiltration (UF) membranes were firstly fabricated from pristine polylactic acid (PLA) with different polymer concentrations using the phase inversion method. The fabricated membranes were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), contact angle, porosity, and pore size analysis. Permeate flux and organic matter (bovine serum albumin (BSA)) rejection were evaluated using synthetic wastewater. The anti-fouling properties of pristine PLA membranes were investigated through static adsorption and dynamic filtration of BSA. Furthermore, the performance of the best performing pristine PLA membrane was evaluated via chemical oxygen demand (COD) rejection as well as membrane fouling using raw municipal wastewater obtained from a local wastewater treatment plant (WWTP) in Abu Dhabi (UAE). The results indicated that increasing the PLA concentration to 20 wt.% improved BSA removal from synthetic and raw wastewaters by up to 92 and 89%, respectively, in addition to improving the membrane anti-fouling property. After selecting the optimum PLA concentration, oxidized multi-walled carbon nanotubes (MWCNT-COOH) were self-assembled with functionalized graphene oxide (fGO), producing fGO/MWCNT-COOH nanocomposite with a very high hydrophilicity and negatively charged surface. The synthesized nanocomposite was integrated into the membrane matrix with different concentrations of 1.5, 3 and 6 wt%. The fabricated membranes were characterized using FT-IR spectroscopy, XRD, SEM, contact angle, porosity, and pore size analysis. The integration of the fGO/MWCNT-COOH nanocomposite into the membranes matrix enhanced the antifouling properties, hydrophilicity and organic removal of the membranes. BSA, and humic acid (HA) were used as synthetic wastewater to test the performance and the antifouling properties of the membranes. It is worth mentioning that when the concentration of fGO/MWCNT-COOH nanoparticles increased from 0 wt% to 6 wt%, the iv FRR values of the fabricated membranes after BSA and HA filtration increased from 89 to 95% and from 94 to 98%, respectively. Furthermore, M2 (with 3 wt% fGO/MWCNT-COOH nanoparticles) had higher rejection rates for BSA and HA, with 95% and 98 %, respectively. Raw wastewater collected from local wastewater treatment plant in Abu Dhabi (UAE) was used to further illustrating the performance of the membrane via measuring chemical oxygen demand (COD). According to the findings of this study, PLA-UF nanocomposite membrane offers a lot of promise for real-world wastewater treatment applications.
Date of AwardDec 2021
Original languageAmerican English

Keywords

  • Polylactic acid; biodegradable; membranes; fouling; nanocomposite; oxidized carbon nanotubes; functionalized graphene oxide; phase inversion; raw wastewater.

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