Reusable Solid-form Phase-Selective Organogelators for Rapid and Efficient Remediation of Crude Oil Spill

Phase-selective organogelators (PSOGs) are considered as a prospective tool for their application in oil spill remediation. However, the number of reports on the PSOGs that can be used in powder form for prompt phase-selective gelation of crude oils is still limited. In this study, a series of compounds with l-mandelic acid as the scaffold bearing different amino acid fragments have been prepared. Also, the gelation behaviors and properties of these derivatives toward organic liquids, product oils, and a type of Chinese crude oil were investigated via heating-and-cooling process, stirring, or resting operation. Besides, the micromorphologies of the resulting gels and the driving forces for the gel formation have been studied by scanning electron microscopy, Fourier transform infrared, UV spectroscopy, concentration-dependent 1H NMR, and X-ray diffraction. Particularly, gelator C15-Phe-Mac-Nap was shown to have the capability of congealing the Chinese crude oil selectively from water in powder form with a relatively lower gelator dosage, as compared with the other gelators we reported in the current and previous works. Moreover, gelator C15-Phe-Mac-Nap displayed some advantageous behaviors such as the reusability of gelator, excellent mechanical and chemical stability of the crude oil gels, and nontoxicity of the gelator in the aquatic environment, indicating its great potential application value for marine oil spill remediation.

Facile and Efficient Phase-Selective Powder Polymer Organogelator for Oil Spill Remediation

Phase-selective organogelators that gel oils from oil/water mixtures are useful to remediate oil spills on water. We designed and synthesized polymer organogelators, poly(styrene-co-10-undecenoic acid) with five different 10-undecenoic acid contents that could be added as powders at room temperature to gel oils with different viscosities. The morphologies and mechanical strengths of the gels were investigated using field-emission electron microscopy and rheological measurements, respectively. The gels formed porous fibrillar structures and had high stiffness. Fourier transformm infrared (FTIR) spectroscopy studies of these gels showed that hydrogen bonding and van der Waals forces helped create three-dimensional networks. The straightforward synthesis procedure, room-temperature conditions, and easy powder delivery make poly(styrene-co-10-undecenoic acid) an attractive alternative to existing oil spill response methods.

Carboxylate Group-Based Phase-Selective Organogelators with a pH-Triggered Recyclable Property

Phase-selective organogelators (PSOGs) have recently attracted more attention because of their advantages in handling oil spills and leaked organic solvents. However, it is difficult to separate and recover the organic phase and PSOGs from organic gels due to the strong interaction between them. Aiming to enhance the separation and recovery performance of the organic phase and PSOGs, we synthesized a series of pH-responsive PSOGs by using itaconic anhydride and fatty amines with carbon chain lengths of C₁₂-C₁₈. Here, PSOGs have an excellent gelation ability in that amounts of organic solvents and fuel oil can be solidified at a low concentration (<3 wt %). It is worth noting that these gels are stronger, which is more convenient for removal by a salvage operation. More importantly, compared with traditional organogelators, pH-responsive PSOGs can easily recover the organic phase and fuel oil with an adjustment of the pH without extraction or distillation. Because of the transformation between the hydrophilicity and hydrophobicity of PSOGs by pH stimulation, 83.15% PSOGs are recovered in three-cycle experiments. In addition, the recycled PSOGs can be used to realize the removal of the organic phase again. Herein, we find that pH-responsive PSOGs could be used as promising and sustainable materials for separating and recovering organic solvents/oils and PSOGs.

Preparation and Application of Superhydrophobic Copper Mesh by Chemical Etching and In-situ Growth

Oily sewage and floating oil in the ocean post a huge threat to the ecological environment, therefore, developing an efficient separation for oil/water mixtures is an urgent need. Currently, superhydrophobic materials exhibit excellent oil/water separation ability. In this study, a superhydrophobic copper mesh prepared by the chemical etching method and the in-situ growth method and the performance evaluation are introduced. The oxide layer on the surface of the copper mesh is first removed by pickling, and then immersed in FeCl₃ solution for chemical etching to make the surface rough, stearic acid (SA) is used for in-situ growth to reduce the surface energy, a superhydrophobic oil-water separation copper mesh is obtained. The water contact angle (WCA) of the copper mesh is more than 160°. The copper mesh is chemically stable and can effectively adsorb floating oil and separate the oil-water mixture. After several oil-water separation experiments, the oil-water separation efficiency can still be above 98%. The effects of the concentration of FeCl₃ and SA on the contact angle and oil-water separation efficiency are investigated, the results show that when the concentration of FeCl₃ is 2% and SA is 1.5%, the WCA and oil-water separation efficiency are the largest. The research used a simple and environmentally friendly method to prepare the oil-water separation copper mesh, which has important application significance for water quality restoration.

Recently Developed Carbohydrate Based Gelators and Their Applications

Carbohydrate based low molecular weight gelators have been an intense subject of study over the past decade. The self-assembling systems built from natural products have high significance as biocompatible materials and renewable resources. The versatile structures available from naturally existing monosaccharides have enriched the molecular libraries that can be used for the construction of gelators. The bottom-up strategy in designing low molecular weight gelators (LMWGs) for a variety of applications has been adopted by many researchers. Rational design, along with some serendipitous discoveries, has resulted in multiple classes of molecular gelators. This review covers the literature from 2017-2020 on monosaccharide based gelators, including common hexoses, pentoses, along with some disaccharides and their derivatives. The structure-based design and structure to gelation property relationships are reviewed first, followed by stimuli-responsive gelators. The last section focuses on the applications of the sugar based gelators, including their utilization in environmental remediation, ion sensing, catalysis, drug delivery and 3D-printing. We will also review the available LMWGs and their structure correlations to the desired properties for different applications. This review aims at elucidating the design principles and structural features that are pertinent to various applications and hope to provide certain guidelines for researchers that are working at the interface of chemistry, biochemistry, and materials science.

How Far Are We in Combating Marine Oil Spills by Using Phase-Selective Organogelators?

Marine oil spills is one of the frequent natural disasters that adversely affect the economy and ecosystem. A variety of methods have been developed to combat marine oil spills. However, none of these methods is ideal and universal for tackling different kinds of oil spills. In addition, most of these methods do not offer the possibility for recovering the spilt oil. There is great interest in developing novel and better methods for combating marine oil spills that allow recovery of the spilt oil. The use of low molecular weight organogelators that can selectively congeal oil from oil-water mixtures have been proposed to be useful for oil spill recovery. From this initial proposal, the area has progressed gradually towards their practical implementation. The advancements and novel concepts in this area are reviewed.

A gelator–starch blend for dry powder based instant solidification of crude oil at room temperature

A sugar based organogelator and natural polymer blend has been found to be useful for the ultrafast, room temperature solidification of crude oil in a dry powder form.