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Iron oxide nanoparticles (FeNPs) based magnetic hydrogels were prepared by in-situ co-precipitation of ferric/ferrous salts during copolymerization of acrylonitrile (AN) and N-vinyl-2-pyrrolidone (NVP) at different molar ratios by emulsion polymerization in the presence of different wt% of kappa-carrageenan (KC) and N, N'-methylenebisacrylamide (MBA)crosslinker. The hydrogels were characterized by FTIR, proton and 13C-NMR, XPS, XRD, DTA-TGA, DLS, VSM, UV-Visible spectroscopy, TEM, EDX, PZC, compressive strength and contact angle measurement. The network parameters of the gel networks were determined from equilibrium swelling using Flory and Rehner model. The nanocomposite gels were used for batch and column adsorption of tetracycline (TC) from water. After repeated adsorptions, the TC-loaded gels were further used for their photocatalytic degradation for safe removal. The NPs-loaded nanocomposite prepared with 5:1 AN:NVP molar ratio, 1 wt% initiator, 1 wt% MBA and 2 wt% KC showed a rejection of 90.2% and an equilibrium adsorption capacity of 38.9 mg/g for continuous adsorption of 50 mg/L TCs in water in a fixed bed of height 25 mm for an inflow rate of 20 ml/min and the same TC-loaded composite showed a photo-degradation efficiency of 86.1% in 2 h. KEYWORDS column adsorption, kappa-carrageenan, nanocomposite adsorbent, nanoparticle, photocatalytic reduction, poly(AN-co-NVP), 1 | INTRODUCTION Tetracyclines(TCs) are available as simple TC or its derivative like oxytetracycline (OTC), doxycycline (DC) and chlorotetracycline (CTC) [1] Structurally TCs consist of four connecting rings having hydroxyl, [...]

Author(s): Zhuo Jiang [sup.1] , Xiaohui Xu [sup.1] , Yanhang Ma [sup.2] , Hae Sung Cho [sup.2] , Deng Ding [sup.1] , Chao Wang [sup.1] , Jie Wu [sup.1] , [...], Metal-organic frameworks (MOFs).sup.1-3 are known for their specific interactions with gas molecules.sup.4,5; this, combined with their rich and ordered porosity, makes them promising candidates for the photocatalytic conversion of gas molecules to useful products.sup.6. However, attempts to use MOFs or MOF-based composites for CO.sub.2 photoreduction.sup.6-13 usually result in far lower CO.sub.2 conversion efficiency than that obtained from state-of-the-art solid-state or molecular catalysts.sup.14-18, even when facilitated by sacrificial reagents. Here we create 'molecular compartments' inside MOF crystals by growing TiO.sub.2 inside different pores of a chromium terephthalate-based MOF (MIL-101) and its derivatives. This allows for synergy between the light-absorbing/electron-generating TiO.sub.2 units and the catalytic metal clusters in the backbones of MOFs, and therefore facilitates photocatalytic CO.sub.2 reduction, concurrent with production of O.sub.2. An apparent quantum efficiency for CO.sub.2 photoreduction of 11.3 per cent at a wavelength of 350 nanometres is observed in a composite that consists of 42 per cent TiO.sub.2 in a MIL-101 derivative, namely, 42%-TiO.sub.2-in-MIL-101-Cr-NO.sub.2. TiO.sub.2 units in one type of compartment in this composite are estimated to be 44 times more active than those in the other type, underlining the role of precise positioning of TiO.sub.2 in this system. Investigation of a chromium-based metal-organic framework shows that the location of added TiO.sub.2 inside specific mesopores strongly affects the ability of the material to catalyse photoreduction of CO.sub.2.