Combined heavy metals and chlorinated organic compounds have been widely reported in industrial wastewater.
Yet, simultaneous removal of these contaminants remains challenging. In this study, a bi-functional composite
(TNTs@AC) was prepared based on commercial titanium dioxide (TiO2) and activated carbon (AC) and tested for
simultaneous removal of Cd(II) and 2-chlorophenol (2-CP). Under the action of high temperature and pressure,
TiO2 was transformed into titanate nanotubes (TNTs) and bound to AC, and in the meanwhile, nanoscale AC
particles were patched on the TNTs. In the mixed TNTs and AC phases, TNTs was responsible for taking up Cd(II),
whereas AC for 2-CP. As such, the relative adsorption capacities of the composite for Cd(II) and 2-CP varied with
the mass ratio of TiO2:AC, with decent uptakes for both chemicals in the mass ratio rage of 1:3 ~1:1. TNTs@AC
(prepared at TiO2:AC = 1:1) demonstrated fast sorption kinetics and high sorption capacities for both Cd(II) and
2-CP, with a maximum Langmuir adsorption capacity of 109 and 52 mg/g, respectively, in the single solute
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Green synthesis of nanoscale anion exchange resin for sustainable water purification
The challenge of providing safe and reliable drinking water is being exacerbated by accelerating population growth, climate change, and the increase of natural and anthropogenic contamination. Current water treatment plants are not effective at the removal of pervasive, hydrophilic, low molecular weight contaminants, which can adversely affect human health. Herein, we describe a green all-aqueous synthesis of an ion exchange resin comprised of short chain polyelectrolyte brushes covalently bound to single walled carbon nanotubes. This composite material is incorporated onto a membrane and the active sites are tested against analyte adsorption. Our control studies of water or brine pushed through these materials, found no evidence of single-walled carbon nanotubes (SWCNTs) or carbon/polymer coming out of the membrane filter. We have measured the adsorption capacity and percentage removal of ten different compounds (pharmaceuticals, pesticides, disinfection byproducts and perfluoroalkylated substances). We have measured their removal with an efficiency up to 95–100%. The synthesis, purification, kinetics, and characterization of the polyelectrolytes, and the subsequent nanoresin are presented below. The materials were tested as thin films. Regeneration capacity was measured up to 20 cycles and the material has been shown to be safe and reusable, enabling them as potential candidates for sustainable water purification.
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- Award ID(s):
- 1724972
- PAR ID:
- 10078403
- Date Published:
- Journal Name:
- Environmental Science: Water Research & Technology
- Volume:
- 4
- Issue:
- 10
- ISSN:
- 2053-1400
- Page Range / eLocation ID:
- 1685 to 1694
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Heat transport in nanoscale carbon materials such as carbon nanotubes and graphene is normally dominated by phonons. Here, measurements of in‐plane thermal conductivity, electrical conductivity, and thermopower are presented from 77–350 K on two films with thickness <100 nm formed from semiconducting single‐walled carbon nanotubes. These measurements are made with silicon–nitride membrane thermal isolation platforms. The two films, formed from disordered networks of tubes with differing tube and bundle size, have very different thermal conductivity. One film matches a simple model of heat conduction assuming constant phonon velocity and mean free path, and 3D Debye heat capacity with a Debye temperature of 770 K. The second film shows a more complicated temperature dependence, with a dramatic drop in a relatively narrow window near 200 K where phonon contributions to thermal conductivity essentially vanish. This causes a corresponding large increase in thermoelectric figure‐of‐merit at the same temperature. A better understanding of this behavior can allow significant improvement in thermoelectric efficiency of these low‐cost earth‐abundant, organic electronic materials. Heat and charge conductivity near room temperature is also presented as a function of doping, which provides further information on the interaction of dopant molecules and phonon transport in disordered nanotube films.
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Modern industrial waste waters often contain high concentrations of phosphate, and many methods have been explored to aid in its removal. This study investigates the use of magnetic nanoparticles as an adsorbent for phosphate removal. Aluminum-doped magnetic nanoparticles were synthesized using a co-precipitation method. Structure and composition analysis of the prepared magnetic nanoparticles indicated an inverse spinal structure with a composition of FeAl0.75Fe1.25O4. These nanoparticles were tested for their phosphate removal properties, including adsorption capacity, selectivity, and kinetic models. They showed great affinity to phosphate with a maximum adsorption capacity of 102 mg/g. Additionally, the adsorption was selective, and the presence of other common anions and organic matters did not interfere with the phosphate adsorption efficacy. The kinetic analysis of phosphate adsorption suggested a pseudo-second-order adsorption behavior, and the adsorption isotherm studies indicated a Langmuir type adsorption. The phosphate removal capabilities of the nanoparticles were also tested in poultry rinsing water, tap water, and municipal wastewaters, all with high phosphate removal efficiency. The overall results from these experiments showed promising results for the phosphate removal efficacy of these nanoparticles.more » « less
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Permeable reactive barriers (PRBs) are a well-known technique for groundwater remediation using industrialized reactive media such as zero-valent iron and activated carbon. Permeable reactive concrete (PRC) is an alternative reactive medium composed of relatively inexpensive materials such as cement and aggregate. A variety of multimodal, simultaneous processes drive remediation of metals from contaminated groundwater within PRC systems due to the complex heterogeneous matrix formed during cement hydration. This research investigated the influence coarse aggregate, portland cement, fly ash, and various combinations had on the removal of lead, cadmium, and zinc in solution. Absorption, adsorption, precipitation, co-precipitation, and internal diffusion of the metals are common mechanisms of removal in the hydrated cement matrix and independent of the aggregate. Local aggregates can be used as the permeable structure also possessing high metal removal capabilities, however calcareous sources of aggregate are preferred due to improved removal with low leachability. Individual adsorption isotherms were linear or curvilinear up, indicating a preferred removal process. For PRC samples, metal saturation was not reached over the range of concentrations tested. Results were then used to compare removal against activated carbon and aggregate-based PRBs by estimating material costs for the remediation of an example heavy metal contaminated Superfund site located in the Midwestern United States, Joplin, Missouri.more » « less
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Multi-walled carbon nanotube (MWCNT) filters incorporated with carbon quantum dots (CDots) or single-walled carbon nanotubes (SWCNTs) were produced for bacteria removal from aqueous solutions and also for inactivating the captured bacteria. TMTP Millipore membranes were used as the base of these filters. The results showed that filters with higher MWCNT loading had higher bacterial removal efficiencies. Filters with a MWCNT loading of 4.5 mg were highly effective at removing bacteria from aqueous solution, resulting in a log reduction of 6.41, 6.41, and 5.41 of E. coli cell numbers in filtrates compared to MWCNT filters without coating, MWCNTs filters with 0.15 mg CDot coating, and MWCNTs filters with 0.15 mg SWCNT coating, respectively. Ionic strength played an important role in bacteria removal. A higher NaCl concentration resulted in higher bacteria removal efficiencies of the filters. Both CDot coatings and SWCNT coatings did not significantly affect the MWCNT filter effects ( P > 0.05). The coatings, especially CDot coatings, significantly inhibited the activities of bacteria retained on the filter surfaces ( P < 0.05). The inhibitory rates were 94.21% or 73.17% on the MWCNT filter surfaces coated with 0.2 mg CDots or SWCNTs, respectively. These results demonstrated that MWCNT filters with CDot coatings were highly effective to remove bacteria from water and to inhibit the activities of the captured bacteria on filter surfaces.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/C8EW00593A
