Carbon Nanodots Embedded on a Polyethersulfone Membrane for Cadmium(II) Removal from Water

Abstract

Cadmium(II) is a toxic heavy metal in aquatic systems. As a potential solution, green carbon nanodots (CNDs) were synthesized from oats and embedded on polyethersulfone membrane (PES) via phase inversion for the adsorption of Cd2+ from water. Characterization techniques for the CNDs and PES membranes were transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), Raman spectroscopy, atomic force microscopy (AFM), contact angle and a pure water flux assessment system operated at 300 kPa. TEM results showed that the CNDs were well dispersed with a uniform shape and size (6.7 ± 2.8 nm). Raman spectroscopy revealed that the CNDs were embedded on the PES and the ID/IG ratio slightly increased, showing that the membranes maintained good structural integrity.The CNDs/PES proved to be more hydrophilic than PES. The glassy carbon electrode (GCE) in anodic stripping voltammetry (ASV) technique detected 99.78% Cd2+ removal by 0.5% CNDs/PES at optimum conditions: 30 min. contact time, at pH 5 and 0.5 ppm Cd2+ solution. The 0.5% CNDs/PES removed Cd(II) due to the hydroxyl group (-OH) and carboxyl group (-COO-) on the membrane composite. It was established that Cu2+ and Pb2+ have a significant interfering effect during the analysis of Cd2+ using GCE in ASV technique. The 0.5% CNDs/PES is recyclable because it removed above 95% of cd2+ in four cycles. In a spiked tap water sample, 58.38% of Cd2+ was sensed by GCE of which 95% was in agreement with the value obtained from inductively coupled plasma optical emission spectrometry (ICPOES).

Anti-Foulant Ultrafiltration Polymer Composite Membranes Incorporated with Composite Activated Carbon/Chitosan and Activated Carbon/Thiolated Chitosan with Enhanced Hydrophilicity

“…This is due to the presence of activated carbon particles on the surface. The porous activated carbon particles present on the surface are the reason for it [33]. The lowest roughness was for the 20% wt.…”

Surface-modified ultrafiltration and nanofiltration membranes for the selective removal of heavy metals and inorganic groundwater contaminants: a review

“…Carbon nanodots (CNDs) synthesized from oats and embedded on the PES membrane demonstrated excellent Cd 2+ removal due to the presence of -OH, -C-O-, and -COO-, which improved membrane hydrophilicity along with increasing negative zeta potential. 33 A 0.5% CNDs/PES rejected 99.78% of Cd 2+ at pH 5 with at least four cycles and >95% efficiency due to the electrostatic interaction between the positively charged cadmium and negatively charged membrane. Eco-friendly photoluminescent carbon dots (CDs) produced from carboxymethylcellulose-CMC and poly(ethyleneimine) (PEI) contain abundant oxygen and nitrogen species and a high graphitization index.…”

“…GO and MWCNTs are also a few carbon-based nanoparticles that can fabricate adsorptive membranes to remove such positively charged cadmium ions. 33,103,166 A TFC membrane was fabricated by considering PES as a support layer and solution of hyperbranched polyethyleneimine (HPEI) in DI water (aqueous phase) and TMC-hexane (organic phase). The as-prepared membranes were soaked immediately into the cysteamine mixture to functionalize the selective layer further.…”

“…29 Conventional remediation techniques for potentially removing these contaminants are chemical precipitation, oxidation using chemicals/photocatalysts, coagulation-flocculation, biosorption, adsorption and ionexchange electrocoagulation, electrodialysis, phytoremediation, phytovolatilization, electrical remediation and thermal desorption methods, membrane technology, etc. 15,17,22,24,26,[30][31][32][33][34] Most of these technologies have a high carbon footprint and demand increased energy and cost, especially for the construction of civil units. The total cost of chemicals for processes such as coagulation and flocculation is also very high, and these chemicals require precision in handling their dosage.…”