Selective adsorption of thiocyanate anions using straw supported ion imprinted polymer prepared by surface imprinting technique combined with RAFT polymerization

RAFT Polymer-Based Surfactants for Minerals Recovery

Reagent consumption is an ongoing sustainability challenge for the mineral processing industry. There is a need to recover, regenerate, and reuse as many of the chemical inputs as possible. This study investigated the design and synthesis via reversible addition-fragmentation chain transfer (RAFT) polymerization of a novel polymer for use as a surfactant in a water-in-oil (w/o) emulsion system for ultrafine minerals recovery. The polymers were designed to hold a thermoresponsive moiety to allow for future recovery. The performance of the novel emulsion was tested for agglomeration of ultrafine talc mineral particles. A traditional emulsion containing sorbitan monooleate as the surfactant was used as a research benchmark to compare against the novel emulsion's stability and performance in minerals recovery. The novel RAFT polymer-based emulsions formed large and stable water droplets surrounded by a halo of smaller water droplets. Over time, the smaller droplets coalesced and a more uniform size distribution of droplets was formed, keeping the emulsion stable. Rheological testing of freshly made and aged emulsions showed both traditional and novel emulsions to have a high viscosity at a low shear rate. RAFT polymer B with a hydrophilic-lipophilic block ratio of 5:10 performed adequately as a surfactant replacement to stabilize w/o emulsions. The mineral recovery using the novel emulsion was on par with the traditional emulsions. The novel RAFT emulsion containing 2.5 wt % polymer B achieved 90% minerals recovery, a similar yield to the traditional emulsions. This study demonstrates that surfactants containing stimuli-responsive moieties can be synthesized via RAFT polymerization and successfully used in mineral processing applications to recover ultrafine particles. Work is ongoing to exploit the stimuli responsiveness to recover the polymer surfactant for reuse.

A newly developed consortium with a highly efficient thiocyanate degradation capacity: A comprehensive investigation of the degradation and detoxification potential

Thiocyanate-containing wastewater harms ecosystems and can cause serious damage to animals and plants, so it is urgent to treat it effectively. In this study, a new efficient thiocyanate-degrading consortium was developed and its degradation characteristics were studied. It was found that up to 154.64 mM thiocyanate could be completely degraded by this consortium over 6 days of incubation, with a maximum degradation rate of 1.53 mM h^-1. High-throughput sequencing analysis showed that Thiobacillus (77.78%) was the predominant thiocyanate-degrading bacterial genus. Plant toxicology tests showed that the germination index of mung bean and rice seeds cultured with media obtained after thiocyanate degradation by the consortium increased by 94% and 84.83%, respectively, compared with the control group without thiocyanate degradation. Cytotoxicity tests showed that thiocyanate without degradation significantly decreased the Neuro-2a cell activity and mitochondrial membrane potential; induced reactive oxygen species generation and apoptosis; increased the cellular Ca²⁺ concentration; and damaged the cell nucleus and DNA. Furthermore, the thiocyanate degradation products produced the consortium were almost totally non-toxic, revealing the same characteristics as those of the control using distilled water. This study shows that the consortium has a high degradation efficiency and detoxification characteristics, as well as great application potential in bioremediation of industrial thiocyanate-containing wastewater.

Synthesis and evaluation of ion-imprinted composite membranes of Cr(vi) based on β-diketone functional monomers

Using Cr(vi) as the imprinted ions and 2-allyl-1,3-diphenyl-1,3-propanedione (ADPD) (a compound synthesized by independent design) as the functional monomer, a series of chromium ion-imprinted composite membranes (Cr(vi)-IICMs) and corresponding non-imprinted composite membranes (NICMs) were synthesized and tested. The results showed that the Cr(vi)-IICM₁₀ membrane prepared under optimal experimental conditions exhibited a high adsorption capacity towards Cr(vi) (Q = 30.35 mg g⁻¹) and a high imprinting factor (α = 2.70). The structural characteristics of Cr(vi)-IICM₁₀ and NICM₁₀ were investigated using FE-SEM, ATR-FTIR, and BET techniques combined with UV-Vis photometry and inductively coupled plasma emission spectrometry (ICP-OES) to evaluate the adsorption performance and permeation selectivity, while the effect on adsorption permeance of varying the experimental conditions including the solvent type, pH, and temperature was also investigated. The results showed that Cr(vi)-IICM₁₀ is a mesoporous material with excellent permeation selectivity, reusability, and favorable pH response, and that its adsorption behavior is in accordance with the Langmuir model and pseudo-first-order kinetics. Thus, Cr(vi)-IICM₁₀ shows great potential towards utilization as a “smart membrane” to control the separation and removal of Cr(vi) in wastewater, and also proved a reasonable design of the new functional monomer ADPD.

Using Cr(vi) as the imprinted ions and 2-allyl-1,3-diphenyl-1,3-propanedione (a compound of independent design) as the functional monomer, a series of chromium ion-imprinted composite membranes and corresponding non-imprinted composite membranes were synthesized and tested.

Unexpected Thiocyanate Adsorption onto Ferrihydrite Under Prebiotic Chemistry Conditions

The most crucial role played by minerals was in the preconcentration of biomolecules or precursors of biomolecules in prebiotic seas. If this step had not occurred, molecular evolution would not have occurred. Thiocyanate is an important molecule in the formation of biomolecules as well as a catalyst for prebiotic reactions. The adsorption of thiocyanate onto ferrihydrite was carried out under pH and ion composition conditions in seawater that resembled those of prebiotic Earth. The seawater used in this work had high Mg²⁺, Ca²⁺ and SO₄^2- concentrations. The most important result of this work was that ferrihydrite adsorbed thiocyanateata pH value (7.2 ± 0.2) that usually does not adsorb thiocyanate. The high adsorptivity of Mg²⁺, Ca²⁺ and SO₄^2-onto ferrihydrite showed that seawater ions can act as carriers of thiocyanate to the ferrihydrite surface, creating a huge outer-sphere complex. Kinetic adsorption and isotherm experiments showed the best fit for the pseudo-second-order model and an activation energy of 23.8 kJ mol^-1forthe Langmuir-Freundlich model, respectively. Thermodynamic data showed positive ΔG values, which apparently contradict the adsorption isotherm data and kinetic data that was obtained. The adsorption of thiocyanate onto ferrihydrite could be explained by coupling with the exergonic SO₄^2- adsorption onto ferrihydrite. The FTIR spectra showed no difference between the C≡N stretching peaks of adsorbed thiocyanate and free thiocyanate, corroborating the formation of an outer-sphere complex. All the results demonstrated the importance of the artificial seawater composition for the adsorption of thiocyanate and for understanding prebiotic chemistry.