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Monodispersed polyethylene glycol diacrylate (PEGDA)/acrylic acid (AA) microgels with a tuneable negative charge and macroporous internal structure have been produced using a Lego-inspired droplet microfluidic device. The surface charge of microgels was controlled by changing the content of AA in the monomer mixture from zero (for noncharged PEGDA beads) to 4 wt%. The macroporosity of the polymer matrix was introduced by adding 20 wt% of 600-MW polyethylene glycol (PEG) as a porogen material into the monomer mixture. The porogen was successfully leached out with acetone after UV-crosslinking, which resulted in micron-sized cylindrical pores with crater-like morphology, uniformly arranged on the microgel surface. Negatively charged PEGDA/AA beads showed improved adsorption capacity towards positively charged organic dyes (methylene blue and rhodamine B) compared to neutral PEGDA beads and high repulsion of negatively charged dye molecules (methyl orange and congo red). Macroporous microgels showed better adsorption properties than nonporous beads, with a maximum adsorption capacity towards methylene blue of 45 mg/g for macroporous PEGDA/AA microgels at pH 8.6, as compared to 23 mg/g for nonporous PEGDA/AA microgels at the same pH. More than 98% of Cu(II) ions were removed from 50 ppm solution at pH 6.7 using 2.7 mg/mL of macroporous PEGDA/AA microgel. The adsorption of cationic species was significantly improved when pH was increased from 3 to 9 due to a higher degree of ionization of AA monomeric units in the polymer network. The synthesized copolymer beads can be used in drug delivery to achieve improved loading capacity of positively charged therapeutic agents and in tissue engineering, where a negative charge of scaffolds coupled with porous structure can help to achieve improved permeability of high-molecular-weight metabolites and nutrients, and anti-fouling activity against negatively charged species. [ABSTRACT FROM AUTHOR]

The aim of the present study was to synthesize a composite of raw interstratified montmorillonite–kaolinite clay (Mt–K) with TiO 2 as an additive by mechanochemical activation and investigate its usability as low-cost adsorbent for simultaneous removal of heavy metals from acidic aqueous solutions. The composite synthesized with amorphous TiO 2 (TiO 2, a) showed a significantly better removal ability of heavy metals from highly acidic solutions (pH = 2.0–4.0) compared with the Mt–K milled for an optimum period of time of 19 h (Mt–K,m) and composite synthesized with crystalline TiO 2 (TiO 2, c). As both of the composites showed the same morphologies, the same distribution of TiO 2 particles on the clay matrix, the same particle size distribution (PSD) dependencies and point of zero charge (pH PZC ) values, it has to be noticed that the difference in the adsorption behavior lies only in the different crystalline forms of the additive, i.e. TiO 2 that was used for the composite preparation. It has been shown that 20% of TiO 2, a was the optimal amount of an additive in the composite to achieve improved adsorption ability. [ABSTRACT FROM AUTHOR]

Separation of yttrium(III) from strontium(II) with 15% (v/v) di(2-ethylhexyl)phosphoric acid (DEHPA) in dodecane was carried out in a hollow fiber supported liquid membrane (SLM) extraction system operated under closed-loop recirculation of the donor and acceptor phase. The donor phase was a mixture of 5.7 mmol dm-3 of Sr(II) and 0.23 mmol dm-3 of Y(III) in 0.1 mol dm-3 HCl, the acceptor solution was 3 mol dm-3 HCl, and the donor to acceptor phase volume ratio was 6.2. At the donor flow rate of 4.7 cm³ min-1 and the acceptor flow rate of 0.8 cm³ min-1, the yield of Y(III) in the acceptor phase (in the form suitable for radiopharmaceutical preparation) reached 60% after 360 min with a molar ratio of Y(III) to Sr(II) in the acceptor of 250:1, as compared to 1:25 in the donor phase. The yield of Y(III) was 72% at the acceptor flow rate to 1.9 cm³ min-1, but a breakthrough of Sr(II) through liquid membrane increased from 0.02 to 0.2%. [ABSTRACT FROM AUTHOR]