Yttrium Residues in MWCNT Enable Assessment of MWCNT Removal during Wastewater Treatment

Abstract

Many analytical techniques have limited sensitivity to quantify multi-walled carbon nanotubes (MWCNTs) at environmentally relevant exposure concentrations in wastewaters. We found that trace metals (e.g., Y, Co, Fe) used in MWCNT synthesis correlated with MWCNT concentrations. Because of low background yttrium (Y) concentrations in wastewater, Y was used to track MWCNT removal by wastewater biomass. Transmission electron microscopy (TEM) imaging and dissolution studies indicated that the residual trace metals were strongly embedded within the MWCNTs. For our specific MWCNT, Y concentration in MWCNTs was 76 µg g−1, and single particle mode inductively coupled plasma mass spectrometry (spICP-MS) was shown viable to detect Y-associated MWCNTs. The detection limit of the specific MWCNTs was 0.82 µg L−1 using Y as a surrogate, compared with >100 µg L−1 for other techniques applied for MWCNT quantification in wastewater biomass. MWCNT removal at wastewater treatment plants (WWTPs) was assessed by dosing MWCNTs (100 µg L−1) in water containing a range of biomass concentrations obtained from wastewater return activated sludge (RAS) collected from a local WWTP. Using high volume to surface area reactors (to limit artifacts of MWCNT loss due to adsorption to vessel walls) and adding 5 g L−1 of total suspended solids (TSS) of RAS (3-h mixing) reduced the MWCNT concentrations from 100 µg L−1 to 2 µg L−1. The results provide an environmentally relevant insight into the fate of MWCNTs across their end of life cycle and aid in regulatory permits that require estimates of engineered nanomaterial removal at WWTPs upon accidental release into sewers from manufacturing facilities.

Effect of MWCNTs Functionalization on Thermal, Electrical, and Ammonia-Sensing Properties of MWCNTs/PMMA and PHB/MWCNTs/PMMA Thin Films Nanocomposites

“…Extraordinary chemical and physical properties of the CNT (i.e. high stability, good conductivity, wide availability and easy functionalization) offer several advantages as compared to other commonly used materials [ 3 , 4 ]. CNTs are much sought after due to their nanoscale size, which confers exceptional thermal, electrical, mechanical, optical, and chemical capabilities [ 5 ].Conducting polymer nanocomposite is formed when the dispersed filler link through CNTs junctions within polymeric matrix.…”

Analytical applications of single particle inductively coupled plasma mass spectrometry: a comprehensive and critical review

“…[131][132][133] Special attention has been paid to the fate of nanoparticles in relation to drinking and wastewater treatments. The stability of Ag nanoparticles under ozonisation conditions 129 and the removal of different engineered nanoparticle through coagulation processes 155 and wastewater treatments [151][152][153][154] have been studied. Soil studies have focused on the interaction of the nanoparticles with soil components, that control their transformations as well as their retention and mobility.…”

“…134,140 Other nanoparticles studied include TiO 2 , 136,144,148,155,156 ZnO, 136,155,156 CeO 2 , 135,144,155,156 CuO, 161 Fe 2 O 3 , 135 Pt 127 and Au. 137,149,155,165 Less common nanoparticles like core-shell Au@Ag nanoparticles 128 and carbon nanotubes 151 have also been considered.…”

“…These measurands are related to the stability of the nanoparticles, but also to their aggregation 110,[122][123][124][125][126][127][128][129]131,133,136,138,139,141,145,148,152,157,158,[162][163][164]166 and dissolution. 138,143,144,147,151 For this reason, the concentration of the dissolved element has also been considered in different studies. 122,123,125,126,131,133,136,144,147,153,154,158 To confirm the formation of aggregates, electron microscopy techniques (SEM, TEM), 110,[123][124][125]141,147,151,…”

“…138,143,144,147,151 For this reason, the concentration of the dissolved element has also been considered in different studies. 122,123,125,126,131,133,136,144,147,153,154,158 To confirm the formation of aggregates, electron microscopy techniques (SEM, TEM), 110,[123][124][125]141,147,151,158,164 DLS 110,124,129,139,158,162,166 or NTA 143 have been used as complementary techniques.…”