NOVELTY - Particulate magnetic nanostructured solid sorbent (MNSS) material comprises a set of nanoparticles tethered together by molecular chains comprising a substantially linear hydrocarbon and/or a poly(alkylene oxide). The ends of the chains connecting the nanoparticles in a three-dimensional elastic network have junction functionality of 2.1-6, with the nanoparticles as junctions of the network. The surfaces of the nanoparticles comprise a polysiloxane bearing sorption-aiding substituents comprising a hydrophilic substituents and/or lipophilic substituents.    USE - The MNSS material is useful for the separation of organic materials such as sugars, lipids, and hydrocarbons from process streams. The sugars are useful for the industrial production of biofuels, bio-based products, and biochemicals.    ADVANTAGE - The MNSS material can significantly simplify the overall biomass conversion process at the pretreatment stage and significantly reduce energy and processing costs.    DETAILED DESCRIPTION - Particulate magnetic nanostructured solid sorbent (MNSS) material comprises a set of nanoparticles tethered together by molecular chains comprising a substantially linear hydrocarbon and/or a poly(alkylene oxide). The ends of the chains connecting the nanoparticles in a three-dimensional elastic network have junction functionality of 2.1-6, with the nanoparticles as junctions of the network. The surfaces of the nanoparticles comprise a polysiloxane bearing sorption-aiding substituents comprising a hydrophilic substituents and/or lipophilic substituents. The set of nanoparticles comprises superparamagnetic nanoparticles or a combination of superparamagnetic and non-magnetic nanoparticles. The superparamagnetic nanoparticles comprise a passivating metal oxide coating around a nanocrystalline metallic core. The cores of the superparamagnetic nanoparticles comprise a nanocrystalline metal or alloy having ferromagnetic or ferrimagnetic properties. INDEPENDENT CLAIMS are included for:    (1) separating a target organic compound from a liquid medium, comprising (a) contacting the liquid medium containing the target organic compound with the MNSS material for a time sufficient to sorb at least a portion of the target organic compound from the aqueous fluid to form a MNSS-target compound complex, and (b) magnetically separating the complex from the aqueous fluid; and    (2) preparing the MNSS material comprising (a1) heating a mixture comprising nanoparticles, a coupling agent, and a polymerizable siloxane monomer, and optionally a solvent, at a temperature and in relative quantities sufficient for the coupling agent to tether the nanoparticles to a selected degree of junction functionality of 2.1-6, and for the siloxane monomer to form a polysiloxane on the surface or in the surface proximity of the nanoparticles to form the particulate MNSS material, and (b1) optionally removing any volatile by-products or solvent from the MNSS material.