Designer carbon nanotubes for contaminant removal in water and wastewater: A critical review

Abstract

The search for effective materials for environmental cleanup is a scientific and technological issue of paramount importance. Among various materials, carbon nanotubes (CNTs) possess unique physicochemical, electrical, and mechanical properties that make them suitable for potential applications as environmental adsorbents, sensors, membranes, and catalysts. Depending on the intended application and the chemical nature of the target contaminants, CNTs can be designed through specific functionalization or modification processes. Designer CNTs can remarkably enhance contaminant removal efficiency and facilitate nanomaterial recovery and regeneration. An increasing number of CNT-based materials have been used to treat diverse organic, inorganic, and biological contaminants. These success stories demonstrate their strong potential in practical applications, including wastewater purification and desalination. However, CNT-based technologies have not been broadly accepted for commercial use due to their prohibitive cost and the complex interactions of CNTs with other abiotic and biotic environmental components. This paper presents a critical review of the existing literature on the interaction of various contaminants with CNTs in water and soil environments. The preparation methods of various designer CNTs (surface functionalized and/or modified) and the functional relationships between their physicochemical characteristics and environmental uses are discussed. This review will also help to identify the research gaps that must be addressed for enhancing the commercial acceptance of CNTs in the environmental remediation industry.

Carbon Nanotubes-Based Nanomaterials and Their Agricultural and Biotechnological Applications

“…Design or modification of CNTs' properties may also assist in the separation of materials following the contaminant treatment process. Nanoparticle separation is facilitated by incorporating a magnetic component into CNTs [129]. It is easy to control the potential and current in the electrochemical technique for wastewater treatment [130,131].…”

“…Schematic diagram representing different modification processes of CNTs for contaminant removal from water and wastewater (C: carbon; CNT: carbon nanotube; ENVT: environmental; Hg: mercury; KOH: potassium hydroxide)[129].…”

Emerging contaminant (triclosan) identification and its treatment: a review

“…Adsorption capacity of MWNT is a function of its structural and physicochemical properties; molecular weight of the compound also has an impact on the adsorption capacity, TCS has shown to have a removal ratio of 0.93 with pristine MWNT, and this was studied by [54]. The fact that CNTs impart toxicity in the environment was tackled by immobilising them; achieved efficiency of TCS removal was up to 99.7% [55]. When compared to other ECs, TCS showed an increased adsorption onto CNTs; this is attributed to its bigger molecules which have greater affinity to adsorb rather than diffusing into the pores of CNTs [56].…”

Kinetics of scandium ion sorption onto oxidized carbon nanotubes

“…Their surface could act as a Lewis base toward polar solutes and is also involved in π-π interactions as well as dispersive interactions with aromatic analytes. Oxidized CNTs, obtained after the introduction of oxygen-containing functional groups (such as -OH, -C=O, and -COOH) on their surface, show high sorption capacity and efficiency for the removal of heavy metal ions [1,4]. CNTs are also employed in combination with other nanoparticles with the aim to improve the removal efficiency [5].…”