Magnetic sorbents based on hypercrosslinked copolymers of styrene and divinylbenzene with immobilized iron oxides

An Overview of Heterogeneous Catalysts Based on Hypercrosslinked Polystyrene for the Synthesis and Transformation of Platform Chemicals Derived from Biomass

Platform chemicals, also known as chemical building blocks, are substances that serve as starting materials for the synthesis of various value-added products, which find a wide range of applications. These chemicals are the key ingredients for many fine and specialty chemicals. Most of the transformations of platform chemicals are catalytic processes, which should meet the requirements of sustainable chemistry: to be not toxic for humans, to be safe for the environment, and to allow multiple reuses of catalytic materials. This paper presents an overview of a new class of heterogeneous catalysts based on nanoparticles of catalytically active metals stabilized by a polymer matrix of hypercrosslinked polystyrene (HPS). This polymeric support is characterized by hierarchical porosity (including meso- and macropores along with micropores), which is important both for the formation of metal nanoparticles and for efficient mass transfer of reactants. The influence of key parameters such as the morphology of nanoparticles (bimetallic versus monometallic) and the presence of functional groups in the polymer matrix on the catalytic properties is considered. Emphasis is placed on the use of this class of heterogeneous catalysts for the conversion of plant polysaccharides into polyols (sorbitol, mannitol, and glycols), hydrogenation of levulinic acid, furfural, oxidation of disaccharides, and some other reactions that might be useful for large-scale industrial processes that aim to be sustainable. Some challenges related to the use of HPS-based catalysts are addressed and multiple perspectives are discussed.

Simultaneous removal of lead, manganese, and copper released from the copper tailings by a novel magnetic modified biosorbent

Potentially toxic elements including lead (Pb), manganese (Mn), and copper (Cu) released from copper tailings would cause severe long-term environmental risks and potential threats to human health. To prevent these negative effects caused by the release of the metals, a novel magnetic carboxyl groups modified bagasse with high adsorption affinity and strong magnetism was synthesized through an in-situ precipitation method and used to simultaneously remove Pb, Mn, and Cu from the eluate of copper tailings. Results showed that release of Pb, Mn, and Cu from the copper tailings was pH, time, and particle size dependent, and maximum concentrations of them released in the eluate was 1.7, 1.9, and 4.1 mg L^-1 under weak acid conditions. Batch adsorption experiment showed that the as-synthesized magnetic modified bagasse could selectively absorb Pb, Mn, and Cu from a complex solution with adsorption capacity of 137.3, 13.1, and 90.0 mg g^-1, respectively. X-ray photoelectron spectroscopy (XPS) and energy dispersive spectroscopy-mapping (EDS-mapping) demonstrated that Pb, Mn, and Cu interacted with the magnetic modified biosorbent mainly through coordination and ion exchange. Column experiments showed that higher than 99.5% of the released Pb, Mn, and Cu could be simultaneously removed by the magnetic modified bagasse, and the maximum concentrations of them released in the eluate of the copper tailings were all decreased to lower than 0.01 mg L^-1, which reached the discharge standards. After recycled by a magnet, the magnetic modified bagasse could be collected easily and used repeatedly. Because of the high efficiency and easy recovery, the used method had great practical application value in removal of potentially toxic elements released from metallic tailings.