Adsorption characteristics of organics in the effluent of ultra-short SRT wastewater treatment by single-walled, multi-walled, and graphitized multi-walled carbon nanotubes

Abstract

With a conceptual shift in sewage treatment from ‘waste pollution’ to ‘vehicle of resource and energy recovery’ and the further intensification of the energy crisis, the separation and recovery of carbon resources from discharged sewage has gained increasing recent attention in the field of water treatment. The ultra-short Solids Retention Time (SRT) activated sludge process (SRT ≤ 4 d) is highly efficient for separating organic matter and improving the energy recovery rate in wastewater treatment plants, but the effluent quality is relatively poor. If organics in the ultra-short SRT effluent can be reduced further to separate and recover carbon resources, the process may soon replace the traditional activated sludge process. We conducted physical adsorption carbon recovery experiments in an ultra-short SRT (SRT = 2 d) activated sludge system using three carbon nanotubes. Considering that Chemical Oxygen Demand (COD) arises from a mixture of organic compounds, and because humic acid (HA) makes up a large fraction of the effluent and can cause great environmental harm, further experiments were conducted on the adsorption of HA in the effluent COD to three nanotubes. This study proposes a novel method to completely remove organics from the effluent from ultra-short SRT activated sludge processes and reveals nanotube adsorption properties and mechanisms.

Influence of Oxygen-Containing Functional Groups on the Environmental Properties, Transformations, and Toxicity of Carbon Nanotubes

“…Notably, increasing NOM aromaticity while maintaining CNT surface chemistry increased both the NOM adsorption capacity and NOM adsorption strength (as modeled using K F and 1/ n , respectively), further evidence for a π–π EDA interaction mechanism . The adsorption of NOM is highly pH-dependent for O-CNTs, decreasing as pH is increased, while pH has a more limited effect on the behavior of pristine or graphitized CNTs. ,, This is because electrostatic repulsion between the ionizable functional groups on NOM and O-CNTs is controlled by pH-dependent deprotonation, while pristine CNTs are not affected by these interactions. , …”

“…203 The adsorption of NOM is highly pH-dependent for O-CNTs, decreasing as pH is increased, while pH has a more limited effect on the behavior of pristine or graphitized CNTs. 114,192,204 This is because electrostatic repulsion between the ionizable functional groups on NOM and O-CNTs is controlled by pHdependent deprotonation, while pristine CNTs are not affected by these interactions. 114,192 The presence of NOM is known to decrease the adsorption of competing compounds by CNTs, 171,172,187,192,205−207 which can result in the decreased impact of CNT surface oxidation on adsorption behavior.…”

Statistical Analysis of a General Adsorption Kinetic Model with Randomness in Its Formulation. An Application to Real Data

“…have followed it [22]. Nevertheless, the emergence of new chemisorption applications, such as water and wastewater treatment processes [2,[7][8][9]38], and new technical advances in spectroscopy or electron microscopy, which have made it possible to analyse the adsorption phenomenon at molecular level [11,20,24,30,36], leads to adsorption kinetics models, which focus especially on the reaction pathways and mechanisms [22].…”

High Adsorption of Benzoic Acid on Single Walled Carbon Nanotube Bundles

“…Carbon-based nanomaterials such as carbon nanotubes (CNTs) are actively explored by environmental scientists both as contaminants of emerging concern and as promising materials for a broad spectrum of nanotechnologies toward improved environmental outcomes [1][2][3][4][5][6][7][8][9][10][11][12][13] . The heightened interest in CNTs in environmental science derives primarily from their unique tubular structures, large specific surface area, tunable surface properties and strong adsorption capacity and affinity for a wide range of environmental chemicals.…”