Synthesis and application of copper-based cholesteryl chloroformate gelator for oil spill remediation

Abstract

Oil spill impact negatively on the environment. Its remediation has been very challenging, and researchers have developed high efficient methods in handling this anomaly, but end up introducing secondary pollutants to the environment. The aim of this study is to synthesise a copper-based organometallogelator with cholesteryl chloroformate and apply it for oil spill remediation in water. In the methodology, the aromatic linker coded CuAL (copper aromatic linker) was first synthesised from a reaction of copper complex (coper reacting with hydrazine) with isophthaloyl chloride, then cholesteryl chloroformate was added to produce a gelator coded CuGe (copper gelator) with the A(LS)₂ (aromatic, linker and steroid) network, which were subsequently characterised. MS results for CuAL and CuGe showed fragments corresponding to the proposed structures, and were both highly crystalline, especially CuGe. Aliphatic primary amines, aromatic rings, aromatic overtones, and conjugated ketones were present in both CuAL and CuGe, with slight variation in peak positions, and the average particle diameter were 5.9 μm (CuAL), and 47.0 μm (CuGe), respectively. The synthesised compounds were thermally stable up to 338 °C (60.1 %) for CuAL and 469.9 °C (74.1 %) for CuGe. Heating-cooling gelation test was positive for methanol, petroleum motor spirit (PMS), kerosene (KSE), and crude oil (COL), with the longest time being 9 min. The highest gelation time and temperature (Tgel) at 2 mg were 3 min (for PMS), and 60 °C for COL respectively. Sorption capacities were 3.0 ± 0.3, 2.0 ± 0.1, and 3.7 ± 0.3 3.0, for PMS, KSE, and COL respectively. The removal efficiency CuGe was 95 % for COL, 89 % for PMS, and 80 % for KSE and is recyclable. In conclusion, a thermally stable, crystalline, eco-friendly, and recyclable copper-cholesteryl chloroformate-based metallogelator has been successfully synthesised. The gelator, CuGe, was successfully applied in the gelation of KSE, PMS, and COL from water with good efficiencies.