Insights into the Simultaneous Sorption of Ciprofloxacin and Heavy Metals Using Functionalized Biochar

Biochar and chitosan are considered as green and cost-effective adsorbents for water purification; the combination of these two materials may lead to an improved adsorption capacity of the generated adsorbents. Most sorption studies have been focused on the ability to adsorb one contaminant or the same type of contaminants. Thus, this study aimed to produce chitosan-biochar beads (CH-BB) and test their efficiency in the simultaneous removal of a metal-complexing antibiotic, ciprofloxacin (CIP), and three metal(loid)s (As, Cd and Pb). Modification of raw pig manure biochar resulted in an increase in its adsorption capacity, except for Pb. The highest increment was observed for As (almost 6-fold) and the lowest was observed for CIP (1.1-fold). The adsorbent was able to simultaneously remove all targeted contaminants, individually and in the mixture. The adsorption capacity of CH-BB followed the order: Pb > Cd > >As > CIP. When Pb and As were present in the same mixture, their removal efficiency increased from 0.13 ± 0.01 to 0.26 ± 0.05 mg/g for As and from 0.75 ± 0.08 to 0.85 ± 0.02 mg/g for Pb due to their co-precipitation. The CIP–metal complexation probably resulted in a reduced adsorption ability for inorganics due to the decreased concentration of free ions. The presence of metals and metalloids led to alterations in CIP’s mobility.

Putting Together the Puzzle of Ion Transfer in Single-Digit Carbon Nanotubes: Ab Initio Meets Mean-Field

Nature employs channel proteins to selectively pass water across cell membranes, which inspires search for bio-mimetic analogues. Carbon nanotube porins (CNTPs) are intriguing mimics of water channels, yet ion transport in CNTPs still poses questions. As alternative to continuum models, here we present a molecular mean-field model, computing ab initio all required thermodynamic quantities for KCl salt and H+ and OH- ions present in water. Starting from water transfer, the model considers transfer of free ions, along with ion-pair formation to address ion-ion interactions. High affinity to hydroxide, suggested by experiments and making it dominant charge carrier in CNTP, is revealed as an exceptionally favorable transfer of KOH pairs. Nevertheless, free ions, coexisting with less mobile ion-pairs, apparently control ion transport. The model explains well the observed effects of salt concentration and pH on conductivity, transport numbers, anion permeation and its activation energies, and current rectification. The proposed approach is extendable to other sub-nanochannels and help design novel osmotic materials and devices.

Speciation of Inorganic Compounds in Aquatic Systems Using Diffusive Gradients in Thin-Films: A Review

The speciation of trace metals in an aquatic system involves the determination of free ions, complexes (labile and non-labile), colloids, and the total dissolved concentration. In this paper, we review the integrated assessment of free ions and labile metal complexes using Diffusive Gradients in Thin-films (DGT), a dynamic speciation technique. The device consists of a diffusive hydrogel layer made of polyacrylamide, backed by a layer of resin (usually Chelex-100) for all trace metals except for Hg. The best results for Hg speciation are obtained with agarose as hydrogel and a thiol-based resin. The diffusive domain controls the diffusion flux of the metal ions and complexes to the resin, which strongly binds all free ions. By using DGT devices with different thicknesses of the diffusive or resin gels and exploiting expressions derived from kinetic models, one can determine the labile concentrations, mobilities, and labilities of different species of an element in an aquatic system. This procedure has been applied to the determination of the organic pool of trace metals in freshwaters or to the characterization of organic and inorganic complexes in sea waters. The concentrations that are obtained represent time-weighted averages (TWA) over the deployment period.

Free ions in kerosene-based ferrofluid detected by impedance spectroscopy

The influence of the free ions on the electric response of cells filled with kerosene-based ferrofluids in the low-frequency region is explored.

Zn(II) Glycine Complexes: an early analysis through a theoretical DFT approach

Amino acids are well described in literature and much information is known about them so far. However, considering the free ions present on living organisms it is likely complexations occur; many works have been released discussing the structures of those species. The complexation of Zn(II) ions and glycine (Gly) results in a stable structure formed by hydrogen interactions between the species. In order to study these interactions, this work uses theoretical approaches to evaluate both structural and electronical information.

The formation of free ions and electrophoretic mobility of Ag and Au nanoparticles in n-hexadecane–chloroform mixtures at low concentrations of AOT

The electrophoretic mobility of Ag and Au nanoparticles in n-hexadecane–chloroform mixtures was studied as a function of the chloroform content (from 0 to 100 vol%).