Application of the anion-exchange resin as a complementary technique to remove residual cyanide complexes in industrial plating wastewater after conventional treatment

Highly Efficient Separation of Ethanol Amines and Cyanides via Ionic Magnetic Mesoporous Nanomaterials

Simple and efficient sample pretreatment methods are important for analysis and detection of chemical warfare agents (CWAs) in environmental and biological samples. Despite many commercial materials or reagents that have been already applied in sample preparation, such as SPE columns, few materials with specificity have been utilized for purification or enrichment. In this study, ionic magnetic mesoporous nanomaterials such as poly(4-VB)@M-MSNs (magnetic mesoporous silicon nanoparticles modified by 4-vinyl benzene sulfonic acid) and Co2+@M-MSNs (magnetic mesoporous silicon nanoparticles modified by cobalt ions) with high absorptivity for ethanol amines (EAs, nitrogen mustard degradation products) and cyanide were successfully synthesized. The special nanomaterials were obtained by modification of magnetic mesoporous particles prepared based on co-precipitation using -SO3H and Co2+. The materials were fully characterized in terms of their composition and structure. The results indicated that poly(4-VB)@M-MSNs or Co2+@M-MSNs had an unambiguous core-shell structure with a BET of 341.7 m2·g-1 and a saturation magnetization intensity of 60.66 emu·g-1 which indicated the good thermal stability. Poly(4-VB)@M-MSNs showed selective adsorption for EAs while the Co2+@M-MSNs were for cyanide, respectively. The adsorption capacity quickly reached the adsorption equilibrium within the 90 s. The saturated adsorption amounts were MDEA = 35.83 mg·g-1, EDEA = 35.00 mg·g-1, TEA = 17.90 mg·g-1 and CN-= 31.48 mg·g-1, respectively. Meanwhile, the adsorption capacities could be maintained at 50-70% after three adsorption-desorption cycles. The adsorption isotherms were confirmed as the Langmuir equation and the Freundlich equation, respectively, and the adsorption mechanism was determined by DFT calculation. The adsorbents were applied for enrichment of targets in actual samples, which showed great potential for the verification of chemical weapons and the destruction of toxic chemicals.

A reaction based carbazole-indolium conjugate probe for the selective detection of environmentally toxic ions

A nucleophilic addition based chemodosimeter was designed and synthesized with a carbazole donor and an indole acceptor. The addition of a cyanide ion to an electron-deficient indole moiety disrupts the acceptor-donor relationship, resulting in noticeable color shifts and spectrum differences in both the absorption and emission profiles. The design has a D-π-A molecular arrangement. Selectivity was investigated in 90% aqueous DMSO solution of probe CI with various anions such as SCN-, PF6-, NO3-, N3-, I-, HSO4-, CN-, H2PO4-, F-, HS-, ClO4-, Cl-, Br-, and AcO-. An intermolecular charge transfer (ICT) band at 506 nm in the UV-visible spectra vanished and the intensity of emission was quenched at 624 nm upon the addition of CN- ions. These outcomes demonstrate the effective nucleophilic addition of cyanide ions to the electron-deficient indole moiety of the probe, resulting in the formation of a new adduct in which the ICT transition is interrupted when π conjugation is blocked. The Job plot, 1H NMR spectroscopy, and HRMS analysis confirmed the formation of a new product. An outstanding response was shown by paper test strips made using probe molecules for the easy detection of cyanide ions in aqueous solutions. Besides, the probe selectively senses cyanide ions in different water samples.

A sustainable management of polycyclic aromatic hydrocarbons to synthesize microporous organic polymers for adsorptive desulphurization of fuels

A sustainable management of carcinogenic polycyclic aromatic hydrocarbons (PAHs) to synthesize a series of high surface area (SABET of 563-1553 m2 g-1) microporous polymeric adsorbents is reported. The products with high yield (>90%) were obtained within only 30 min at a low temperature of 50 °C using a microwave-assisted approach with 400 W microwave power followed by 30 min of ageing by raising the temperature to 80 °C. The synthesized adsorbents are used for removing another category of carcinogenic pollutants i.e., polycyclic aromatic sulphur heterocycles (PASHs) from model and real fuels. Adsorptive desulphurization experiment in batch mode could reduce the sulphur from high concentrated model (100 ppm) and real (102 ppm) fuels to 8 ppm and 45 ppm respectively. Similarly, desulphurization of model and real fuels with ultralow sulphur concentrations of 10 and 9 ppm, respectively, reduced the final concentration of sulphur to 0.2 and 3 ppm, respectively. Adsorption isotherms, kinetics, and thermodynamic studies have been conducted using batch mode experiments. Adsorptive desulphurization using fixed bed column studies show the breakthrough capacities of 18.6 and 8.2 mgS g-1, for the same high concentrated model and real fuels, respectively. The breakthrough capacities of 1.1 and 0.6 mgS g-1 are estimated for the ultralow sulphur model and real fuels, respectively. The adsorption mechanism, based on the spectroscopic analysis (FTIR and XPS) demonstrates the role of π-π interactions between the adsorbate and adsorbent. The adsorptive desulphurization studies of model and real fuels from batch to fixed bed column mode would offer an in-depth understanding to demonstrate the lab-scale findings for industrial applications. Thus, the present sustainable strategy could manage two classes of carcinogenic petrochemical pollutants, PAHs and PASHs, simultaneously.

Effective immobilization of bisphenol A utilizing activated biochar incorporated into soil: combined with batch adsorption and fixed-bed column studies

This study presented the mixture of biochar and soil for removal of bisphenol A (BPA) to assess environmental remediation ability. Using phoenix tree leaves as biomass and phosphoric acid as activator, after one-step hydrothermal and short-term activation, the eventual solid product was phosphoric acid hydrothermal activated carbon (HPC). The characterizations showed that HPC had the high specific surface (994.21 m2·g-1), and large unsaturated esters and hydroxyl groups. The saturated adsorption capacities of batch and column adsorption for the addition of 0.5% HPC to soil were 0.790 mg·g-1 and 67.23 mg·kg-1, while to the natural soil were 0.236 mg·g-1 and 8.75 mg·kg-1, respectively. The adsorption kinetics and thermodynamic analysis indicated that the adsorption process utilizing HPC incorporated into soil was a chemical reaction rate-controlled, physical-dominated multilayer adsorption, and spontaneous endothermic. Also, batch adsorption experiments and analysis were performed under different pH levels, HPC contents, organic acid concentrations, and cationic strengths. Successively, fixed-bed column experiments were carried out with and without the HPC; the results showed that the wide mass transfer zone led to the effective fixation of BPA, and the organic acid had no obvious effect on the fixation of BPA when the 1.0% HPC mixed with soil. Finally, through characterizations and data analysis, the enhanced adsorption of BPA by HPC mixed with soil mainly relied on π-π interaction, hydrogen bonding, followed by electrostatic attraction and pore filling.

Nanoscale Ion-Exchange Materials: From Analytical Chemistry to Industrial and Biomedical Applications

Nano-sized ion exchangers (NIEs) combine the properties of common bulk ion-exchange polymers with the unique advantages of downsizing into nanoparticulate matter. In particular, being by nature milti-charged ions exchangers, NIEs possess high reactivity and stability in suspensions. This brief review provides an introduction to the emerging landscape of various NIE materials and summarizes their actual and potential applications. Special attention is paid to the different methods of NIE fabrication and studying their ion-exchange behavior. Critically discussed are different examples of using NIEs in chemical analysis, e.g., as solid-phase extraction materials, ion chromatography separating phases, modifiers for capillary electrophoresis, etc., and in industry (fuel cells, catalysis, water softening). Also brought into focus is the potential of NIEs for controlled drug and contrast agent delivery.

Enhanced removal of metal-cyanide complexes from wastewater by Fe-impregnated biochar: Adsorption performance and removal mechanism

Metal-cyanide complexes are common contaminants in industrial wastewater. Removal of these refractory contaminants is essential before their discharge into the environment. This study investigated a biochar (BC)-based sorbent material that could be applied for the efficient removal of metal-cyanide complexes from wastewater. In consideration of the strong electrostatic repulsion of the pristine BC toward anions, iron-modified BC (Fe-BC) composites were fabricated by a one-step co-pyrolysis of corn straw and FeCl₃ at 600-800 °C. The adsorption performance and corresponding sorption mechanisms of representative metal-cyanide complexes (ferricyanide [Fe(CN)₆]^3- and tetracyanonickelate [Ni(CN)₄]^2-) onto the Fe-BC composites were investigated. The results indicated that the Fe-BC composites had significantly high affinity toward the metal-cyanide complexes, reaching a maximum sorption capacity of 580.96 mg/g for [Fe(CN)₆]^3- and 588.86 mg/g for [Ni (CN)₄]^2-. A mechanistic study revealed that Fe-impregnation during BC fabrication could effectively alter the negatively charged BC surface, forming more functional groups that could interact with the metal-cyanide complexes. Moreover, the transformation of carbon structure promoted the carbothermal reduction process, leading to the formation of various reductive-Fe minerals in the resulting Fe-BC composites. These modification-induced alterations to the surface and structural characteristics of BC were expected to facilitate the adsorption/precipitation of target contaminants. Different sorption mechanisms were proposed for the two metal-cyanide complexes that were the focus of this study. For [Fe(CN)₆]^3-, precipitation by Fe-bearing species in the Fe-BC composites was the major factor controlling [Fe(CN)₆]^3- removal, while for [Ni(CN)₄]^2- hydrogen bonding interactions between surface functional groups (especially hydroxyl (-OH) and carboxyl (-COOH)) and [Ni(CN)₄]^2- were the main factors controlling removal.

Effectiveness and mechanism of cyanide remediation from contaminated soils using thermally activated persulfate

Persulfate (PS)-based advanced oxidation processes have been frequently employed for contaminant remediation, but the effectiveness of PS oxidation for the elimination of cyanide-bearing contaminants from soil, and the underlying mechanisms, have rarely been explored. This study investigated the degradation of two iron-cyanide (Fe-CN) complexes (ferricyanide and ferrocyanide) with thermally activated PS via two remediation strategies, namely one-step oxidation (direct PS oxidation) and two-step oxidation (alkaline extraction followed by PS oxidation). The two-step oxidation process was more effective for the elimination of cyanide pollutants from soil, reaching >94% remediation efficiency for both Fe-CN complexes studied. The presence of dissolved soil components, especially soil organic matter, increased consumption of PS during the remediation process. A combined analysis based on electron paramagnetic resonance (EPR), free radical scavenging, and degradation product identification revealed that SO₄^- and HO were the principal reactive radicals responsible for Fe-CN degradation. Based on the determination of radical species and identification of decomposition products, a transformation pathway for Fe-CN complexes during thermally activated PS oxidation is proposed. Overall, this study demonstrates the effectiveness of the thermally activated PS oxidation technique for cyanide elimination from polluted soil. Further study is required to verify the feasibility of this method for field applications.

A practical approach for the determination of environmental quality standards-based discharge limits: the case of Tersakan sub-basin of Yeşilırmak River in Turkey

The control of point source discharges to rivers has become more significant since the establishment of environmental quality standards (EQSs). Many countries, including Turkey, have set EQS values for various contaminants. One important challenge regarding these EQSs is to reconcile the effluent limits that are technically and economically achievable with the ones that are required to accomplish the EQSs. The Tersakan sub-basin of Yeşilırmak River acquires good examples of this challenge due to the industrial and agricultural discharge activities present. In this study, a new, simplistic, and less data-driven approach is developed to facilitate this compromise and implemented for all suitable discharge points within the sub-basin. The foundation of this approach is that effluent discharges may mix and become diluted within negligibly short distances from the point of discharge where exceedance of EQSs can be permissible. The approach modularly combines different analytical solutions of the advective-dispersive mass transport equation that are applicable under different mixing conditions and estimates maximum allowable discharge concentrations of contaminants. The results of the case study in the Tersakan sub-basinindicate that none of the studied discharges need load reduction to achieve EQSs. However, in various points, tridecane, nickel, bis(2-ethylhexyl) terephthalate, NH₄-N, total phosphorus, and free cyanide have consumed more than 10% of their discharge quotas estimated by the mentioned approach. Therefore, for the sub-basin, these six contaminants and their corresponding two discharge points may require more attention in the future.