Removal of paraquat herbicide from water by textile coated with anionic cyclodextrin polymer

Plant extracts as an eco-friendly approach to remove paraquat from aqueous solution

Nowadays, water pollution by herbicides is known as a global concern. Paraquat (PQ) (1-1-methyl-4,4-bi-pyridinium-dichloride) is a chip with high performance, which is being widely used herbicide to remove weeds from agricultural and natural ecosystems. PQ can contaminate water sources due to its high solubility in water. Human death by poisoning effects of PQ has been reported in several countries. Therefore, the side effects of PQ are a global challenge. This study aimed to investigate the bioremediation of PQ by plant extracts, as a low-cost, nontoxic, and natural absorbent to remove PQ from aqueous solutions in different conditions. In this regard, the extracts of common purslane (portulaca oleracea), florist kalanchoe (kalanchoe blossfeldiana), and jade plant (crassula portulaca) were used as adsorbents. For this purpose, the effect of various parameters such as contact time, initial concentration of PQ solution, temperature, pH, and amount of extract was investigated. The results of present study showed that P. oleracea extract and C. portulaca extracts have higher adsorption efficiency than k. blossfeldiana extract. The highest PQ removal was obtained by P. oleracea extract (79.04%) and C. portulaca extract (78.72%) at pH = 11, the adsorbent content of 0.2 mg L-1, and the lowest absorption of PQ (50.6%) was obtained by K. blossfeldiana extract. The highest PQ removal by plant extract was observed at 30 min for P. oleracea and C. portulaca, and at 15 min for k. blossfeldiana extract. Moreover, surface absorption capacity increased with increasing plant extract concentration, decreasing PQ concentration and decreased with increasing temperature. Finally, it can be concluded that plant extract can help to remove PQ from the aqueous solution.

Occurrence of herbicides in the aquatic environment and their removal using advanced oxidation processes: a critical review

Herbicides are chemicals used globally to kill unwanted plants so as to obtain high agricultural yields and good agricultural products. Herbicides are sometimes transported from the farmlands into water bodies mainly through runoffs. These chemicals are recalcitrant, and their accumulation is hazardous to abiotic and biotic components of the ecosystem. At present, the best alternative technology for elimination of herbicides in water is the usage of advanced oxidation processes (AOPs). The AOPs, which are performed homogeneously or heterogeneously, are capable of breaking down complex pollutants in water into carbon dioxide and mineral compounds. In these processes, ^·OH is produced and used for degradation process. It is recommended that the total organic carbon (TOC) produced during degradation reaction be monitored because the ‧OH produced or generated can react to form intermediates before complete mineralisation is achieved. Different kinds of AOPs for degradation of herbicides have their specific advantages as well as limitations. This report shows that AOPs are excellent techniques for degradation of herbicides in aqueous solutions, and the mechanisms showed that herbicides were mineralised. The amount and type of photocatalysts, pH of the medium, surface characteristics of the photocatalysts, doping of the photocatalysts, temperature of the medium, concentration of herbicides, presence of competing ions, intensity and irradiation period, and type of oxidants have great influence on the degradation of herbicides in water. Overall, this report showed that most AOPs could not completely degrade herbicides in water and complete degradation can be achieved by developing novel and robust AOPs that will completely mineralise herbicides in water-this will pave way for water and environmental safety.

Adsorption of Cationic Pollutants from Water by Cotton Rope Coated with Cyclodextrin Polymers

The contamination from perilous organic compounds (pesticide and dyes) in water generates a significant problem for the environment and humans. A modified textile was prepared by a coating of anionic cyclodextrin polymer, obtained from the cross-linking between citric acid and β-cyclodextrin in the presence of poly (vinyl alcohol), on the cotton cord for cationic pollutant removal from an aqueous solution. Its physicochemical properties were also characterized by gravimetry, titration, stereomicroscopy, SEM, TGA, ¹³C NMR, and ATR-FTIR. The CC2 system exhibited 79.2% coating yield, 1.12 mmol/g COOH groups, 91.3% paraquat (PQ) removal, 97.0% methylene blue (MB) removal, and 98.3% crystal violet (CV) removal for 25 mg/L of initial concentration. The kinetics was fitted to the pseudo-second-order model using 6 h of contact time. The isotherm was suitable for the Langmuir isotherm with a maximum adsorption of 26.9 mg/g (PQ), 23.7 mg/g (MB), and 30.3 mg/g (CV). After 120 h of contact time in water and 5% v/v of HCI in ethanol, the weight loss was 7.5% and 5.6%, respectively. Finally, the recyclability performance reached 84.8% (PQ), 95.2% (MB), and 96.9% (CV) after five reuses.

Cotton Cord Coated with Cyclodextrin Polymers for Paraquat Removal from Water

The contamination of hazardous agrochemical substances in water caused essential trouble for humans and the environment. The functional textile was used as an effective adsorbent for paraquat removal from an aqueous solution. The coating of anionic cyclodextrin polymer, issued from the cross-linking between 1,2,3,4-butanetetracarboxylic acid and β−cyclodextrin in the presence of poly (vinyl alcohol), on the cotton cord, was firstly investigated. Their physicochemical characteristics were also characterized by gravimetry, acid–base titration, ATR-FTIR, ¹³C NMR, TGA, and stereo-microscopy. The BDP5 system revealed 107.3% coating yield, 1.13 mmol/g COOH groups, and 95.1% paraquat removal for 25 mg/L of initial concentration. The pseudo-second-order model was appropriate for kinetics using 6 h of contact time. Langmuir isotherm was suitable with the maximum adsorption of 30.3 mg/g for paraquat adsorption. The weight loss was 10.7% and 7.8%, respectively, for water and 5% v/v of HCI in ethanol after 120 h of contact time. Finally, the reusability efficiency stayed at 88.9% after five regeneration.

Comparison of Paraquat Herbicide Removal from Aqueous Solutions using Nanoscale Zero-Valent Iron-Pumice/Diatomite Composites

Paraquat is the most important herbicide of the bipyridyl group. The aim of the present study was to compare the removal of paraquat herbicide from aqueous solutions using nanoscale zero-valent iron-pumice/diatomite composites. In this study, nZVI was supported with diatomite and pumice. Scanning electron microscopy (SEM) analysis, X-ray diffraction spectroscopy (XRD), Fourier transform infrared spectrometry (FTIR), and specific surface area tests (BET) were used to evaluate the properties of nanoadsorbents. The residual concentration of paraquat in aqueous solution was detected by high-performance liquid chromatography (HPLC). Then, the effects of different variables including the pollutant concentration, contact time, temperature, adsorbents (D-nZVI and P-nZVI) dose, and pH, were investigated in a lab scale batch system. The results showed that the optimal pH for both processes was 3.74. In optimal conditions, the efficiencies of D-nZVI and P-nZVI were 92.76% and 85.28%, respectively. In addition, isotherm and adsorption kinetics studies indicated that P-nZVI follows the Langmuir and Freundlich isotherm models, and D-nZVI follows the Langmuir isotherm model, and both processes follow pseudo-second-order kinetics. The results indicated that the synthesized nanoparticles were suitable for removing paraquat from aqueous solutions. Both adsorbents were found to be very effective in removing similar compounds at ambient temperature in a short time.

In vitro removal of paraquat and diquat from aqueous media using raw and calcined basil seed

Raw and calcined basil seeds (BS and BS1000, respectively) were evaluated for their ability to remove herbicides such as paraquat and diquat. The physicochemical properties of BS and BS1000 were determined and the effects of contact time and initial concentration on paraquat and diquat adsorption were assessed. After calcination treatment, the number of pores in BS increased, and the specific surface area was increased from 0.265 to 86.902 m² g^-1. The quantity of herbicides adsorbed using BS1000 was greater than that using either BS or medicinal-grade carbon. Additionally, the adsorption quantity increased with the increase in contact time and initial concentration of herbicide. Therefore, BS1000 is a potential resource for the removal of herbicides. Moreover, BS and BS1000 exhibited the capacity for herbicide adsorption in simulated intestinal fluid.

Cyclodextrin Polymers and Cyclodextrin-Containing Polysaccharides for Water Remediation

Chemical pollution of water has raised great concerns among citizens, lawmakers, and nearly all manufacturing industries. As the legislation addressing liquid effluents becomes more stringent, water companies are increasingly scrutinized for their environmental performance. In this context, emergent contaminants represent a major challenge, and the remediation of water bodies and wastewater demands alternative sorbent materials. One of the most promising adsorbing materials for micropolluted water environments involves cyclodextrin (CD) polymers and cyclodextrin-containing polysaccharides. Although cyclodextrins are water-soluble and, thus, unusable as adsorbents in aqueous media, they can be feasibly polymerized by using different crosslinkers such as epichlorohydrin, polycarboxylic acids, and glutaraldehyde. Likewise, with those coupling agents or after substituting hydroxyl groups with more reactive moieties, cyclodextrin units can be covalently attached to a pre-existing polysaccharide. In this direction, the functionalization of chitosan, cellulose, carboxymethyl cellulose, and other carbohydrate polymers with CDs is vastly found in the literature. For the system containing CDs to be used for remediation purposes, there are benefits from a synergy that arises from (i) the ability of CD units to interact selectively with a broad spectrum of molecules, forming inclusion complexes and higher-order supramolecular assemblies, (ii) the functional groups of the crosslinker comonomers, (iii) the three-dimensional structure of the crosslinked network, and/or (iv) the intrinsic characteristics of the polysaccharide backbone. In view of the most recent contributions regarding CD-based copolymers and CD-containing polysaccharides, this review discusses their performance as adsorbents in micropolluted water environments, as well as their interaction patterns, addressing the influence of their structural and physicochemical properties and their functionalization.