Polymeric Micro-Ribbons Engineering for Wastes Oil and Mercury Removal from Water - 22193

The oil spills and heavy metal pollutions in water systems are ever-present threats in environments. Powerful absorbents have been designed for waste oil cleaning and heavy metal abatement. However, the post-treatments, for example, recycling the used absorbents and enriching the absorbed substance, can be still challenging in a large-scale water system where a filtration unit can not be easily set up. We developed a novel type of micro-ribbon (MR) absorbent based on polydimethylsiloxane (PDMS) using a simple synthesis route including one step anisotropically thermally oxidizing the PDMS film on a glass slide. The synthesized PDMS-MRs contain a high aspect-ratio, highly curly shape, high surface area, and tunable surface hydrophobicity. The PDMS-MRs absorbent shows an excellent performance in oil/water separation. This is attributed to the high surface area (comparable to that for single-wall carbon nanotubes) and the hydrophobic surface. A mixture of 40 mL pump oil and 200 mL water can be separated within a few seconds using ∼ 0.5 g of PDMS-MRs with a separation efficiency > 95%. In another hand, the PDMS-MRs also showed a good potential in water-soluble mercury abatement. A removal efficiency > 75% was obtained after 60 min cleaning of a 10 mL solution containing ∼0.5 ppm Hg²⁺ using 10 mg of PDMS-MRs. Moreover, controlled thermal heating of the PDMS-MRs in the air will convert the original methyl group-rich surfaces into hydroxyl group-rich surfaces. This hydroxyl group-rich surface can be further functionalized using various types of molecules according to the need and be converted into absorbents for different target pollutants. For example, we proved that the thiol groups can be introduced by forming a self-assembled monolayer of mercaptopropyltrimethoxysilane (MPTMS) onto the oxidized PDMS-MRs surface. We will test the efficiency of organic mercury abatement using the PDMS-MRs functionalized with thiol groups. One unique character that makes the PDMS-MRs outstanding other micro/nano-particle absorbents is that the PDMS-MRs self-entangle and form cage-like networks in water after stirring which is due to the hydrophobicity and the geometrical shape. This character allows a facile separation of the used PDMSMRs from the water and efficient enrichment of the pollutant without using any filtration or collecting devices. Recently, our collaborators at SIUC have found that magnetic field responsive PDMS-MRs can be synthesized by embedding magnetic nanoparticles in the MRs. We will explore the potential of applying magnetic PDMS-MRs for oil removal and mercury abatement to realize an easy-to-recycle water cleaning process. Finally, the entire synthesis route is time-efficient, inexpensive, and uncomplicated. It is ideal for a roll-to-roll process for large-scale and continuous PDMS-MRs fabrication. The glass slide can be cleaned and reused which significantly reduces the cost. PDMS is a biocompatible material that has been used for many biological and/or biomedical devices engineering. No biohazard materials were employed during the synthesis. We believe that the PDMS-MRs and functionalized PDMS-MRs have great potential of being applied for high efficiency, easy-to recycle, and environmentally friendly water cleaning when one or multiple types of pollutants are present. (authors)