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Spent ion exchange resins have become a crucial radioactive solid waste from the nuclear industry. Developing effective and safe disposal methods as alternatives to the present cementation method remains challenging. This investigation demonstrates the treatment of a mixed resin (sulfonated and quaternary ammonium polystyrene beads with a weight ratio of 40%:60%) by the electro-Fenton process. Mesh-type titanium metal that was coated with IrO 2 /RuO 2 (Ti-DSA) was used as the anode and a stainless steel net was used as the cathode. The conversion of resins to soluble fragments and the removal of total organic carbon reached 92% and 99.4%, respectively, under conditions of solid loading = 40g L −1 , pH 2, applied current = 2 A, H 2 O 2 flow rate = 1.2 mL min −1 , FeSO 4 = 20 mM at 85 °C. A pseudo first-order kinetic model of consecutive reactions specified that the efficacy of the electro-Fenton depended strongly on the slowly generated styrene in the aqueous phase by H 2 O 2 and strong acid, which was rapidly mineralized by the hydroxyl radicals. The electro-Fenton process with reused iron catalyst was effective for treating ion exchange resin for at least for three runs, greatly reducing the volume of waste resin liquid. [ABSTRACT FROM AUTHOR]

• Cu/Ni electrodes were successfully prepared using electrodeless method. • Depositing time affected the morphology and crystal facet distribution of Cu. • The Cu{1 1 1} facet played a significant role on nitrate reduction. • Nitrogen selectivity was 55.6% at >−0.6 V vs. Hg/HgO. • Complete nitrate reduction occurred at <−0.6 V vs. Hg/HgO. Cu/Ni composite electrodes were prepared and studied for the electrochemical reduction of nitrate in aqueous solutions. Electrodeless plating technique, with tartrate as chelatant and formaldehyde as reducing agent, enabled the in-situ incorporation of Cu nanoparticles into the open-pore structured Ni foam to form Cu-Ni composite electrodes. X-ray diffractometer (XRD) and scanning electron microscopy (SEM) revealed that the crystal facet and grain morphology of Cu nanoparticles was closely controlled by the plating time and played a significant role in nitrate reduction and nitrogen selectivity. Cyclic voltammetry provided information on the electron transfer between surface nitrogen species and Cu/Ni electrodes. Electrochemical nitrate reduction was initiated at the onset potential of Cu(0)/Cu(I) redox reaction over a potential window of −0.6 V to −1.2 V. The preferential Cu{1 1 1} facet orientation improved the electron transfer process. Batch kinetics studies at constant current and potential showed that specific adsorption of nitrate and nitrite on the Cu{1 1 1} facet was critical to efficient electrochemical nitrate reduction. Moreover, the conversion of nitrogenous byproduct was potential-dependent. Results showed that N 2 selectivity was high (55.6%) at low overpotential (i.e., ⩾ −0.6 V vs. Hg/HgO. At high overpotential (i.e, <−0.6 V) there was complete of NO 3 − reduction with NH 4 + as major byproduct. [ABSTRACT FROM AUTHOR]

• Simultaneous recovery of phosphorus and potassium from urine was achieved. • Recovery of P and K reached 98.4% and 70.5%, respectively at low Mg:K ratio of 1.25. • K-struvite pellets recovered have low water content and high purity (>95%). • The fluidized bed homogeneous crystallization (FBHC) was performed without seeds. • FBHC recovery can help yield a profit of $0.26/m3-urine. Most of nutrients in municipal wastewater originate from human urine. In this study, a novel fluidized-bed homogeneous crystallization process was developed for the simultaneous recovery of phosphorus (P) and potassium (K) from synthetic human urine. The operational variables including pH, Mg:K ratios and up-flow velocity were tested in the laboratory. The total removal of P and K (TR%) reached 98.4% and 70.5%, respectively, and the crystallization ratios (CR%) were 86.5% and 62.3%, respectively, at conditions of pH 10 ± 0.2, molar ratio Mg:K = 1.25, initial concentrations 850 mg P/L and 1830 mg K/L. The SEM and XRD analyses showed that the fluidized bed homogeneous crystallization (FBHC) product was pure magnesium potassium phosphate (K-struvite) (average size = 0.85 mm; purity = 95 ± 3%). The modelling of minimum fluidization velocity (MFV) resulted in values of up-flow 1.5–2.0 times the MFV for the effective fluidization. The profit of the recovery of P and K from human urine via FBHC process could be $0.26/m3-urine. [ABSTRACT FROM AUTHOR]