Rapid uptake of atrazine from aqueous phase by thermally activated MCM-41
Graphical abstract
Introduction
The practice of insecticides, pesticides and herbicides in agriculture has been continually growing to meet the high demand for foodstuffs at global level (Yu et al., 2018). Pesticides are primarily used to resist pests, weeds, insects, and other arthropods; however, regular exposure to pesticides may cause hazardous effects on non-target organisms (Jamil et al., 2011). Among various pesticides, atrazine (1-chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine) is extensively used in plant nurseries, forestry, agriculture and landscaping projects (Zhang et al., 2018; Zhu et al., 2018). Owing to low cost and high efficiency against a broad range of target organisms, atrazine comprising compounds have been in use for over 50 years (Stara et al., 2018). Atrazine (AZN) also poses several threats to humans, amphibians, wildlife and aquatic species, and therefore, it is considered as a potential endocrine disruptor compounds (Wirbisky et al., 2016). Endocrine disrupting compounds (EDCs) can be identified as exogenous molecules that cause destruction with the hormone system by mimicking or manipulating natural hormones of exposed organisms (Goyal et al., 2016a). Consequently, presence of EDCs in water, food, and soil has become a worldwide trouble due to their hazardous activity at even slight doses, which can disturb endocrine activities due to structure resemblance with natural hormones (Goyal et al., 2016b). Due to improper handling, leakages, mobility in soil (owing to high water solubility), and long half-life (approx. 4 years), atrazine is found in various samples of ground and surface water resources as collected from Asia, Europe, Australia and America (Salazar-Ledesma et al., 2018; Montiel-León et al., 2019). Plenty of studies reported that atrazine has been found at concentrations of 3 parts per billion (ppb; μg/L) which is many times that of the maximum permissible limit (MPL) set by the United States Environmental Protection Agency (EPA) (Wirbisky and Freeman, 2017; Salazar-Ledesma et al., 2018; Montiel-León et al., 2019). Several biological assays have reported that atrazine can induce abnormal functions in nervous, gastro, endocrine, reproductive, immune, cardiovascular, renal and respiratory systems along with genetic alterations which can cause cancerous tumors (Kale et al., 2018; Wirbisky et al., 2016). Therefore, removal strategy for the deterioration of atrazine from the ecosystem should be strictly implemented.
So far, a number of novel processes such as nano-scale zero-valent iron, cavitation, electrochemical advanced oxidation, phytoextraction, biodegradation and adsorption-separation have been applied for the treatment of atrazine-contaminated water (Jawale et al., 2018; Wu et al., 2018; Komtchou et al., 2017; Derakhshan et al., 2018; Qu et al., 2018; Abigail and Das, 2015; Goli et al., 2020). Among these processes, adsorption has been proven to be less expensive, easily adoptable, highly effective and less toxic method (Goyal et al., 2018a; Labiadh and Kamali, 2019). However, carbonaceous substances such as graphene, coal fly ash, activated carbon and carbon nano-tubes have been employed very commonly for deletion of atrazine from wastewater streams (Li et al., 2014; Chen et al., 2009; Goli et al., 2020). But, due to high cost, non-biodegradability, excess of toxic products, there is a need to synthesize low-cost, reusable and environmentally friendly adsorbents (Goyal et al., 2016c, Goyal et al., 2018b). In this context, the use of mobil composition of matter No. 41 (MCM-41) as an excellent adsorbent for the adsorption of organic as well as inorganic contaminants has obtained considerable attention in the recent past (Chen et al., 2015). Various studies suggested that MCM-41 is a suitable candidate to trap organic contaminants from aqueous phase owing to abundant accessibility, cost-effectiveness, reusability, and extraordinary ion-exchange/sorption capabilities (Shao et al., 2014; Soltani et al., 2018). Pei et al. (2019) synthesized MCM-41/MgO nanocomposite having a high surface area (1000 m2/g) and meso-structure which has shown adsorption capacity of 1861.38 mg/g for the removal of crystal violet dye. Moreover, Rizzi et al. (2019) also studied the removal of blue dye (300 mg/g) by the amine impregnation onto MCM-41. Additionally, MCM-41 has also been shown excellent removal of ciprofloxacin via both batch and column adsorption technology (Lu et al., 2020).
In this research, we have investigated the prospect of using MCM-41 in robust reusable form to remove atrazine from the synthetic wastewater without implementing any chemical modification. Several sintering temperatures (250–750 °C) were used for the physical activation of the synthesized adsorbent which was proved to be an effective treatment for the maximum removal of atrazine. Whereas, textural and physico-chemical properties of the hierarchically synthesized adsorbent were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared microscopy (FT-IR), and Brunner Emmett Teller (BET) methods. Subsequently, its effectiveness was evaluated in the sorption performance of atrazine using batch adsorption procedure. A few adsorption parameters were optimized along with comprehensive kinetic and equilibrium isotherm model studies; and eventually the potential implementation of fabricated MCM-41 was determined in reusability studies. The mentioned sorbent is freshly synthesized and has not been evaluated previously for the adsorption/separation of the pesticide atrazine till date.
Section snippets
Chemicals and reagents
Fumed silica (SiO2), hexadecyltrimethylammonium bromide (C19H42BrN), and aluminum hydroxide (Al(OH)3) were purchased from Sigma-Aldrich and others were purchased from TCI chemicals, Japan. Atrazine (Purity: 97%, C8H14ClN5), ethyl alcohol (C2H5OH) and ultra pure water were used to prepare standard atrazine solutions. All chemicals and reagents purchased were of standard grade.
Synthesis process of MCM-41
The MCM-41 was fabricated by hydrothermal treatment procedure (Abboud et al., 2018; Silva et al., 2017). Initially, fumed
Characterization of the adsorbent
The crystalline phases of prepared MCM-41 samples were recorded in the 2θ short-angle X-ray diffraction (SAXD) by X-ray diffractometer (X'PERT-PRO) at an acceleration voltage of 40 kV. Fig. 1 represents the SAXD patterns of MCM-41 calcined at different temperatures; and MCM-41 (650) showed a similar pattern as reported in literature (Chen et al., 2015; Shao et al., 2014). Moreover, SAXD describes the structure of MCM-41 in a better way and the peak that can be seen at 2θ = 2.4° is associated
Conclusion
The synthesized MCM-41 (650) is an excellent adsorbent for the removal of atrazine from aqueous phase. The adsorbent can be physically activated at high temperatures without any addition of harmful reagents. It was successfully characterized by various physiochemical techniques and found to have porous structure. The solution factors such as pH (2–12), temperature (20–40 °C), MCM-41 (650) dose (0.1–2 g/L) extremely affected the removal rate of atrazine from the simulated wastewater.
CRediT authorship contribution statement
Nitin Goyal: Conceptualization, Methodology, Investigation, Writing - original draft. Vijaya Kumar Bulasara: Project administration, Funding acquisition, Supervision, Writing - review & editing. Gang Li: Project administration, Funding acquisition, Supervision, Writing - review & editing. Liying Liu: Project administration, Funding acquisition, Supervision, Writing - review & editing.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgment
This research study was supported by National Natural Science Foundation of China (Grant: 51406029), Project of Xingliao talents (XLYC1807119), and Fundamental Research Funds for the Central Universities (Grants: N172504027 & N182508027).
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