Magnetic Hybrid Alg/TiO2/FeNPs Triads for the Efficient Removal of Pollutants in Water

Nurfatyha Rusydah, Mohamad Shahdad (2018) Magnetic Hybrid Alg/TiO2/FeNPs Triads for the Efficient Removal of Pollutants in Water. Masters thesis, Universiti Malaysia Sarawak (UNIMAS).

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Abstract

Nanocomposite materials have been receiving considerable attention in wastewater treatment due to their improved photocatalytic efficiency. However, solutions are needed to cope with problem arise from the formation of titanium dioxide (Ti02) slurry in the treated water. In this context, the possibility to use photocatalytic magnetic nanoparticles to ease separation from the treated water offers an appealing solution. A facile non-thermal method was applied to synthesize a hybrid nanocomposite consisting of Ti02/caicium alginate (Alg) and magnetite nanoparticles (FeNPs) referred to as AIg/Ti02/FeNPs. The efficiency of AIg/Ti02/FeNPs was assessed for the removal of methylene blue (MB) and a mixture of three heavy metals (MHM) consisting of Cr(III), Cu(II) and Pb(II) ions in aqueous solutions under ultraviolet (UVC) irradiation (/...=254 nm). The potential of adsorbent Alg as a barrier to prevent direct contact between magnetic core and Ti02 was investigated by varying the concentrations of sodium hydroxide (NaOH) and Alg. The performance of four different synthesized AIg/Ti02IFeNPs samples (AIglTi02IFe-l, AIg/Ti02IFe-2, AIglTi021Fe-3 and AIg/Ti02/Fe-4) was found to be fairly comparable and stable based on their efficiency in removing MB from aqueous solution due to the physico-chemical characterization (surface morphology, functional groups, and elemental analysis) which supports the performance of AIg/Ti02/FeNPs. For the optimization study using the response surface methodology (RSM) with three factorial Box-Behnken experimental designs, 0.2 g of AIg/Ti02/Fe-2 was chosen as it exhibited the highest MB removal of 97.6% for an initial concentration of 5 ppm of MB after 120 min treatment under UYC irradiation. Among the three independent variables studied (i.e., pH, contact time and initial MB concentration), the initial concentration of MB had significant effect towards the MB removal performance. A recycling study was done and confirmed the stability of Alg/Ti02lFe-2 up to 3 cycles, with only a slight drop in the removal efficiency from 93.1 % to iv 88.5%. For MHM removal, 0.6 g of AIglTi02IFe-2 was selected as the optimized adsorbent dosage. Similar parameters as in MB removal were investigated for the removal of MHM using RSM via Box-Behnken design. Removal percentages of Pb(II), Cr(III), and Cu(lI) ions in the aqueous solution mixture solution were 99.6%, 98.6%, and 98.4%, respectively under optimized conditions ofpH 6.80 and 44 ppm within 72 min of irradiation. The removal of Pb(lI) ions was the highest as it exhibited the smallest degree of hydration of metal ions precursor compared to Cr(IlI) and Cu(II) ions. Thus, this made Pb(U) ions to be easily adsorbed onto the surface of AIg/Ti02/Fe-2. The recycling experiments showed no significant changes with only slight increment of Pb(lI) ions in the second cycle when the AIglTi02IFe-2 beads were retrieved and reused in three consecutive cycles of the heavy metals removal. This finding again confirmed the stability of AIglTi02IFe-2 when reused repeatedly in the photocatalytic treatment of multi-heavy metals solution. Hence, the fabricated AIglTi02/FeNPs nanocomposites could be a potential functional material for treating artificial dye and heavy metals laden wastewater.

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