Molecular imprinting technology for next-generation water treatment
Published on by Water Network Research, Official research team of The Water Network in Academic
Molecular imprinting technology for next-generation water treatment via photocatalysis and selective pollutant adsorption
Author links open overlay panelYoussef Aoulad El Hadj Ali a, Abdelmonaim Azzouz a, Mohammadi Ahrouch a, Abderrahman Lamaoui b, Nadeem Raza c, Abdellatif Ait
Abstract
With the growth of industry and agriculture, contaminants such as pharmaceuticals, pesticides, phenolic residues, heavy metals, among others, have been caused serious pollution of water bodies and soil, so it is very urgently needed to find highly efficacious and cost-effective materials to remove these pollutants from environment. Owing to their low molecular weight, not easily degraded and long-term presence in the aquatic environment, super-stable mineralization effect, easily modifiable surfaces, and anion intercalation properties, molecular imprinted polymers (MIPs) present unique advantages in the removal of emerging pollutants. It is very critical to understand the mechanism of pharmaceuticals, pesticides, phenolic residues, dyes, and heavy metals removal by MIPs for the subsequent design of the adsorbent and photodegradation materials structure. Herein, we discuss the recent advancements in the applications of MIPs in water treatment, with a major focus on their use in adsorption and photocatalysis. The preparation methods and characterization of MIPs intended for water treatment are discussed at the beginning of this review. Then it discusses the potential of MIPs-based nanocomposites for the selective photocatalytic degradation and adsorption of a wide range of pollutants in water. Finally, a summary and the ongoing research efforts in this field is further provided.
Graphical Abstract
Schematic illustration of the Molecular imprinting technology for next-generation water treatment via photocatalysis and selective pollutant adsorption
Introduction
Water pollution, due to a fast-developing economy and industrialization, has emerged as one of the most important hazards for mankind [1], [2]. A wide range of organic and inorganic pollutants (e.g., pharmaceutical residues, pesticides, dyes, heavy metals, and phenol residues) are hazardous to human health and the environment [3], [4], [5] due to their stability to sunlight irradiation and their high resistance to biodegradation [6]. Hence, it is essential to design an efficient treatment technologies to eliminate these pollutants from the environment.
To treat wastewater, a variety of processes are applied to eliminate contaminants from the environment. Among the most employed approaches are separation, adsorption, photocatalytic degradation, and membrane filtration [7], [8], [9], [10]. However, conventional adsorbents and catalysts, such as activated carbons, zeolites, ion exchange resins, and organic resins, have a low ability to pollutants elimination [11]. In addition, partial catalysts have inferior charge separation efficiency, recyclability, and chemical stability, which may lead to secondary pollution of water sources and do not meet the requirements of ecology, energy saving, and renewables in the field of modern environmental protection [12]. Therefore, investigators have been attempting to exploit an affordable and cost-efficient composite material with superb specific surface area, high separation, and strong reusability.
Today, the literature reports the use of molecularly imprinted polymers (MIPs) as a potentially powerful tool for the elimination of trace pollutants from water. Molecular imprinting technology (MIT) is an upcoming technology in which the synthesis of a material is carried out in the presence of a template molecule; subsequent removal of the template results in a material with "memory" sites capable of selectively recognizing and re-binding the original template from a mixture [13], [14]. The key merits of MIPs are their simple preparation, high stability in harsh conditions, long lifetime, and the possibility of creating "tailor-made" binding sites by simply adapting the synthesis procedure to the desired target molecule employed as a template used during polymerization [15], [16]. These methods have overcome many issues of conventional approaches, being low cost, with low energy consumption, and also low environmental impact [13].
As compared to other materials, MIPs have a much higher selectivity and a higher tendency to be modified and combined with other materials [17]. MIPs have raised considerable interest in the field of sorptive extraction techniques [18], [19], [20], adsorption [21], [22], [23], photocatalysis [24], [25], electrochemical sensors [26], [27], catalysts [28], enzyme mimics [29]. MIPs can be assembled with different materials, such as metal oxides [30], magnetic nanoparticles [31], [32]; MXenes [33], carbonaceous materials (e.g., graphene [34], graphene quantum dots [35], reduced graphene carbon nanotubes [36]), and metal-organic frameworks (MOFs) [37], to create innovative composite materials with a variety of functionalities. One of the fundamental shortcomings of conventional photocatalysts is the wide band gap, which restricts their applicability in several different fields. Among the endeavors to overcome this disadvantage, the combining of MIP with miscellaneous materials such as metal oxides can reduce the band gap of the target photocatalyst and facilitate its use in the degradation of pollutants by LED light or sunlight. Therefore, the adsorption and catalysis performance of MIPs-nanocomposites are distinctly enhanced compared with the original MIPs [21]. In the field of wastewater treatment, the huge application potential and broad application prospects of MIPs have made them one of the most significant areas of interest in the last decades.
In more recent years, scientists have been investing a lot of research and experiments in the application of MIP materials in wastewater treatment, and with the rise of green production and environmental protection, the interest of researchers in this field will continue to increase (Fig. 1). Previously, various review articles have been published to summarize and explore the adsorption and photocatalytic degradation of pharmaceutical residues, pesticides, dyes, phenol residues, and heavy metal ions from contaminated water by MIPs [22], [38], [39], [40]. For example, Zare et al . reported the use of MIPs for the removal of pharmaceuticals from water and wastewater [38]. In addition, Guan et al .demonstrate recent exploits in the innovative deployment of molecular printing-based technology to selectively adsorb and photocatalytically degrade organic contaminants [40]. However, this review provides the most recent advances in the applications of MIPs in the adsorption and photocatalytic degradation to remove various pollutants from environmental water. The elimination mechanism of several water pollutants, such as heavy metal ions, pharmaceutical residues, dyes, phenol residues, and pesticides, enables the readers to understand the various strategies to design and fabricate pristine MIP composites and derivatives. This review article will also serve as an inspiration to explore the fabrication and synthesis processes of new MIP nanocompounds, as well as provides effective ideas for making higher-quality adsorbents and catalysts. Additionally, we have provided an up-to-date performance comparison of different MIPs for the removal of diverse hazardous pollutants from water.
Taxonomy
- Pollutants
- Water Pollution
- Treatment
- Ion Exchange
- Treatment Methods
- Biological Treatment
- Wastewater Treatment
- Biological Treatment
- Absorbents