Impact of Source Water Quality on Multiwall Carbon Nanotube Coagulation

Abstract

Potable water treatment facilities may become an important barrier in limiting human exposure to engineered nanoparticles (ENPs) as ENPs begin to contaminate natural aquatic systems. Coagulation of ENPs will likely be a major process that controls the ENP fate and the subsequent removal in the aqueous phase. The influence that source water quality has on ENP coagulation is still relatively unknown. The current study uses a 2(3) x 2(4-1) fractional factorial design to identify seven key surface water constituents that affect multiwall carbon nanotube (MWCNT) coagulation. These seven factors include: influent concentrations of kaolin, organic matter (OM), alginate, and MWCNTs; type and dosage of coagulant; and method of MWCNT stabilization. MWCNT removal was most affected by coagulant type and dosage, with alum outperforming ferric chloride at circumneutral pH. None of the other factors were universally significant but instead depended on coagulant type, dose, and method of stabilization. In all cases where factors were found to have a significant impact on MWCNT removal, however, the relationship was consistent: higher influent concentrations of kaolin and alginate improved MWCNT removal while higher influent concentrations of OM hindered MWCNT coagulation. Once MWCNTs are released into the natural environment, their coagulation behavior will be determined by the type and quantity of pollutants (i.e., factors) present in the aquatic environment and are governed by the same mechanisms that influence the colloidal stability of "natural" nanoparticles.

Effect of Dissolved Organic Matter on Agglomeration and Removal of CuO Nanoparticles by Coagulation

“…Removal of Cu up to 95% was achieved at the OD of coagulant Al 2 O 3 /L (Figure 3). These results suggest a dependency of CuO NPs removal on the source water characteristics and dosage of applied coagulant as demonstrated in earlier studies [21,22]. The results in Figure 3 further show the key role of DOM characteristics on the coagulant dose and overall performance of the coagulation process.…”

“…The high removal of CuO NPs in these conditions may also be attributed to the presence of metal cations (K + , Mg 2+ ). Holbrook et al demonstrated that the specific adsorption of divalent cation increased the NPs agglomeration at a wide range of pH levels in a complex environment [22].…”

Methodological considerations for testing the ecotoxicity of carbon nanotubes and fullerenes: Review

“…The life cycle of many NPs is expected to include their release into wastewater treatment plants as a primary route through which they might ultimately enter the environment [6][7][8]. The potential for different steps in the wastewater treatment plant to remove CNPs, therefore, has also been investigated [18][19][20]. Based on the likely scenarios for CNPs to arrive in the environment, it is possible to indicate the types of ecosystems likely to be contaminated and the organisms that are of highest priority for testing the negative effects of CNPs (Fig.…”

Coagulation and Dissolution of CuO Nanoparticles in the Presence of Dissolved Organic Matter Under Different pH Values

“…Coagulation is an efficient and simple process commonly used in water treatment to remove suspended solids, organic and inorganic substances from the water. Earlier studies [17][18][19] reported that NPs including cadmium telluride (CdTe), C(60), and multiwall carbon nanotubes (MWCNT) were efficiently removed from water by alum as well as polyaluminum chloride (PACl) coagulation. In addition, variable coagulation efficiencies of different ENPs, such as Ag (2-21%), ZnO (46-98%) and TiO 2 (2-9%) have also been reported [20].…”