Piperazine-functionalized porous anion exchange membranes for efficient acid recovery by diffusion dialysis

A simple method to prepare anion exchange membrane by PVA/EVOH/MIDA for acid recovery by diffusion dialysis

Given the substantial environmental pollution from industrial expansion, environmental protection has become particularly important. Nowadays, anion exchange membranes (AEMs) are widely used in wastewater treatment. With the use of polyvinyl alcohol (PVA), ethylene-vinyl alcohol (EVOH) copolymer, and methyl iminodiacetic acid (MIDA), a series of cross-linked AEMs were successfully prepared using the solvent casting technique, and the network structure was formed in the membranes due to the cross-linking reaction between PVA/EVOH and MIDA. Fourier transform infrared spectrometer, X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy were used to analyze the prepared membranes. At the same time, its comprehensive properties which include water uptake, linear expansion rate, ion exchange capacity, thermal stability, chemical stability, and mechanical stability were thoroughly researched. In addition, diffusion dialysis performance in practical applications was also studied in detail. The acid dialysis coefficient (UH+) ranged from 10.2 to 35.6 × 10-3 m/h. Separation factor (S) value ranged from 25 to 38, which were all larger than that of the commercial membrane DF-120 (UH+: 8.5 × 10-3 m/h, S: 18.5). The prepared membranes had potential application value in acid recovery.

Design of tropinium-functionalized anion exchange membranes for acid recovery via diffusion dialysis process

Diffusion dialysis (DD) process utilizing anion exchange membranes (AEMs) is an environmentally-friendly and energy-efficient technology. From acidic wastewater, DD is needed for acid recovery. This research reports the development of a series of dense tropinium-functionalized AEMs via solution casting method. Fourier Infrared transform (FTIR) spectroscopy verified the successful preparation of AEMs. The developed AEMs exhibited a dense morphology, featuring 0.98-2.42 mmol/g of ion exchange capacity (IEC), 30-81% of water uptake (W_R) and 7-32% of linear swelling ratio (LSR). They displayed exceptional mechanical, thermal and chemical stability and were employed for acid waste treatment from HCl/FeCl₂ mixtures via DD process. AEMs possessed 20 to 59 (10^-3 m/h) and 166 to 362 of acid diffusion dialysis coefficient (U_H⁺) and separation factor (S) respectively at 25 °C. Compared to DF-120 commercial membrane (U_H⁺ = 0.004 m/h, S = 24.3), their DD efficiency was improved under identical experimental conditions.

Effective Removal of Fe (III) from Strongly Acidic Wastewater by Pyridine-Modified Chitosan: Synthesis, Efficiency, and Mechanism

A novel pyridine-modified chitosan (PYCS) adsorbent was prepared in a multistep procedure including the successive grafting of 2-(chloromethyl) pyridine hydrochloride and crosslinking with glutaraldehyde. Then, the as-prepared materials were used as adsorbents for the removal of metal ions from acidic wastewater. Batch adsorption experiments were carried out to study the impact of various factors such as solution pH value, contact time, temperature, and Fe (III) concentration. The results showed that the absorbent exhibited a high capacity of Fe (III) and the maximum adsorption capacity was up to 66.20 mg/g under optimal experimental conditions (the adsorption time = 12 h, pH = 2.5, and T = 303 K). Adsorption kinetics and isotherm data were accurately described by the pseudo-second-order kinetic model and Sips model, respectively. Thermodynamic studies confirmed that the adsorption was a spontaneous endothermic process. Moreover, the adsorption mechanism was investigated using Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The results revealed the pyridine group forms a stable chelate with iron (III) ions. Therefore, this acid-resistant adsorbent exhibited excellent adsorption performance for heavy metal ions from acidic wastewater compared to the conventional adsorbents, helping realize direct decontamination and secondary utilization.

Ferrous Industrial Wastes-Valuable Resources for Water and Wastewater Decontamination

Ferrous waste by-products from the metallurgical industry have a high potential for valorization in the context of the circular economy, and can be converted to value-added products used in environmental remediation. This research reviews the latest data available in the literature with a focus on: (i) sources from which these types of iron-based wastes originate; (ii) the types of ferrous compounds that result from different industries; (iii) the different methods (with respect to the circular economy) used to convert them into products applied in water and wastewater decontamination; (iv) the harmful effects ferrous wastes can have on the environment and human health; and (v) the future perspectives for these types of waste.

Effective removal of Pb(II) ions using piperazine-modified magnetic graphene oxide nanocomposite; optimization by response surface methodology

In this research, the piperazine-modified magnetic graphene oxide (Pip@MGO) nanocomposite was synthesized and utilized as a nano-adsorbent for the removal of Pb(II) ions from environmental water and wastewater samples. The physicochemical properties of Pip@MGO nanocomposite was characterized by X-ray diffraction analysis (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray spectroscopy (EDAX), Thermo-gravimetric analysis (TGA), Vibrating Sample Magnetometery (VSM) and Fourier-transform infrared spectroscopy (FT-IR) analysis. In this method, the batch removal process were designed by response surface methodology (RSM) based on a central composite design (CCD) model. The results indicated that the highest efficiency of Pb(II) removal was obtained from the quadratic model under optimum conditions of prominent parameters (initial pH 6.0, adsorbent dosage 7 mg, initial concentration of lead 15 mg L⁻¹ and contact time 27.5 min). Adsorption data showed that lead ions uptake on Pip@MGO nanocomposite followed the Langmuir isotherm model equation and pseudo-second order kinetic model. High adsorption capacity (558.2 mg g⁻¹) and easy magnetic separation capability showed that the synthesized Pip@MGO nanocomposite has great potential for the removal of Pb(II) ions from contaminated wastewaters.