A green process for the conversion of hazardous sintering dust into K2SO4 and NH4Cl fertilizers.

Sintering dust from the steelmaking industry is a hazardous waste that is rich in valuable metals. The purpose with the present study has been to design an efficient process for the preparation of K2SO4 and NH4Cl fertilizers by using sintering dust as raw material. The K, S, and Cl in the sintering dust were selectively and efficiently leached using water. The leaching of Ca impurities was then greatly reduced and the appearance of Zn and Mg was avoided. The Cl- ions in the leachate were, thereafter, adsorbed by a 201 × 7 resin to form a K2SO4 solution. Finally, the loaded Cl- on the resin was desorbed to form a NH4Cl solution, and the resin was regenerated and recycled. The purified solutions were crystallized to prepare K2SO4(s) and NH4Cl(s) products, which met the national standard of China for superior potassium sulfate and ammonium chloride, to be used for agricultural use. The recoveries of K, Cl, and S from the sintering dust were 80.78%, 92.63%, and 93.92%, respectively. Notably, the Mn content in the leaching residue increased from 9.08% to 14.19%. This could be used for the conversion of Mn impurities into recyclable manganese-rich raw materials. This green process enables an effective extraction of important impurities in hazardous sintering dust, thereby providing a new potassium source for potash fertilizer manufacturing with notable economic and environmental benefits.

Highly efficient poly(6-acryloylamino-N-hydroxyhexanamide) resin for adsorption of heavy metal ions.

Heavy metal wastewater pollution has become an ecological challenge worldwide. This study reports the development of a novel poly (6-acryloylamino-N-hydroxyhexanamide) (PAHHA) resin for effective adsorption of heavy metal ions, including Cu2+, Pb2+ and Ni2+. The chelating resin was synthesized by the grafting reaction between 6-amino-N-hydroxyhexanamide and polyacrylic resin, thus containing the hydroxamate and acylamino groups. The batch adsorption experiments revealed that the PAHHA resin exhibited an excellent adsorption performance for Cu2+, Pb2+ and Ni2+. The maximum adsorption capacities of Cu2+, Pb2+ and Ni2+ were determined to be 238.59, 232.48 and 115.77 mg·g-1, respectively. Based on the adsorption kinetics, the pseudo-second-order kinetic model was noted to fit well for all metal ions. The metal ion concentration as a function of the equilibrium adsorption capacity fitted well with the Langmuir isotherm, thus indicating the single layer adsorption process. The adsorption mechanism was investigated by using Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), density functional theory (DFT) calculations, X-ray photoelectron spectroscopy (XPS) and adsorption isotherms. It was revealed that the PAHHA resin possessed multiple active sites, including -CONHOH, -CONH- and -COOH, which could strongly adsorb the metal ions. Specifically, the -CONHOH group displayed a high affinity by forming a stable five-membered ring with heavy metal ions. Overall, the developed resin exhibits advantages such as simple synthesis, inexpensive raw material and good recyclability, along with high adsorption ability, thus providing a new approach for efficiently treating wastewater contaminated with heavy metal ions.

Preparation of an Anti-Aggregation Silica/Zinc/Graphene Oxide Nanocomposite with Enhanced Adsorption Capacity.

Nanomaterials play a significant role in adsorption treatment of dye wastewater, but irreversible aggregation of nanoparticles poses a significant problem. In this work, nanomesoporous zinc-doped silicate (NMSZ) was prepared by an in situ method. To prevent agglomeration, NMSZ was covalently bonded to graphene oxide (GO) sheets to form a nano-silica/zinc/graphene oxide composite (GO-NMSZ), aimed at removal of cationic dye methylene blue (MB). For comparison, undoped mesoporous silica (MS) was also synthesized and modified to obtain a silica/graphene oxide composite (GO-MS). The materials were characterized by powder XRD, SEM, FTIR spectroscopy, TEM, nitrogen sorption, and X-ray photoelectron spectroscopy (XPS). Preservation of the oxygen-containing groups of GO in the composites led to higher adsorption capacities. The best GO-NMSZ composite exhibited an enhanced adsorption capacity of 100.4 mg g-1 for MB compared to those of undoped GO-MS (80.1 mg g-1 ) and nongrafted NMSZ (55.7 mg g-1 ). The nonselective character of GO-NMSZ is demonstrated by effective adsorption of anionic dye Congo red (127.4 mg g-1 ) and neutral dye isatin (289.0 mg g-1 ). The adsorption kinetics, adsorption isotherms, and a thermodynamic study suggested that MB adsorption occurs by chemisorption and is endothermic in nature.

Novel Sodium O-Benzythioethyl Xanthate Surfactant: Synthesis, DFT Calculation and Adsorption Mechanism on Chalcopyrite Surface.

Xanthate with low cost and strong collecting ability has great application in the recovery of sulfide mineral. Herein, a xanthate, sodium O-benzythioethyl xanthate (SBEX), with high collecting ability was prepared by introducing thioether structure, which was constructed by reactive 2-(benzylthio)ethanol, carbon disulfide, and sodium hydroxide. The flotation performance of SBEX to chalcopyrite is yet to be explored by flotation experimental, surface tension measurements, adsorption experimental, density functional theory (DFT) calculations, and X-ray photoelectron spectroscopy (XPS) analyses. It is found that the thioether structure can increase the hydrophobicity and adsorption amount of SBEX on chalcopyrite surface, and SBEX features a higher collecting recovery toward chalcopyrite than sodium isobutyl xanthate (SIBX) and sodium phenylethyl xanthate (SPEX). The adsorption mechanism analyses reveal that two S atoms in the structure of -C(═S)-S are the reactive sites that can donate their electrons to minerals, as confirmed by DFT calculations and XPS analyses.

Preparation of a novel resin with acyl and thiourea groups and its properties for Cu(II) removal from aqueous solution.

In this paper, a new resin (PIDTR) containing acyl and thiourea chelating groups was synthesized and its adsorption performances and mechanism to Cu(II) were investigated by adsorption tests, BET, SEM, FTIR and XPS analyses. Equilibrium data were fitted well with Langmuir model with the maximum adsorption capacity of 1.1608 mmol g-1 for Cu(II) at pH 5.0. The regeneration and reusability test showed that the adsorption capacities decreased from 0.917 mmol g-1 to 0.88 mmol g-1 after five cycles of adsorption and desorption. The thermodynamics showed that the adsorption process was spontaneous and endothermic. The adsorption dynamic demonstrated that two stages in the adsorption process: liquid film diffusion and chemical adsorption. The studies of SEM indicated that Cu(II) ions were adsorbed on the surface of PIDTR. FTIR and XPS analysis further proved that Cu(II) ions were chemisorbed on the surface of PIDTR by formation of CuN, CuO and CuS bonds with the breakage of NH, C=O and S=C bonds in PIDTR.

Highly efficient Mn2+, Mg2+, and NH4+ recovery from electrolytic manganese residue via leaching, solvent extraction, coprecipitation, and atmospheric oxidation.

Electrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, exhibits substantial leaching toxicity owing to its elevated levels of soluble Mn2+ and NH4+. The leaching and recovery of valuable metal ions and NH4+ from EMR are key to the hazard-free treatment and resource utilization of EMR. In this study, two-stage countercurrent leaching with water was used to leach Mn2+, Mg2+, and NH4+ from EMR. Subsequently, two-stage countercurrent extraction was conducted using α-hydroxy-2-ethylhexyl phosphinic acid (α-H-2-EHA) as an extractant to enrich Mn2+, and Mg2+, and NH4+ were recovered via coprecipitation. Based on the calculations for a single leaching-extraction process, the recoveries of Mn2+, Mg2+, and NH4+ ions exceeded 80%, 99%, and 90%, respectively. In addition, high-purity Mn3O4 with an Mn content of 71.61% and struvite were produced. This process represents a win-win strategy that facilitates the hazard-free treatment of EMR while simultaneously recovering valuable Mn2+, Mg2+, and NH4+ resources from waste. Thus, this study provides a novel approach to the hazard-free and resourceful management of solid waste. ENVIRONMENTAL IMPLICATION: Electrolytic manganese residue (EMR), a solid waste generated during electrolytic manganese production, poses significant environmental risks due to its soluble heavy metals and ammonia nitrogen content. Efforts have been made to address this issue, but there has been no mature industrial application due to cost or processing capacity constraints. In this work, solvent extraction was first used to enrich Mn2+ from EMR leachate, and a novel α­hydroxy­2­ethylhexyl phosphinic acid was used as extractant. High purity Mn3O4 and struvite was synthesized through this process. The win­win strategy offers a novel approach for the hazard­free and resourceful utilization of solid waste.

High-efficiency selective leaching of valuable metals from spent lithium-ion batteries: Effects of Na2S2O8 on the leaching of metals.

A new method was presented for the high-efficiency selective leaching of Li and the efficient recovery of transition metals (TMs) from the cathode materials of spent lithium-ion batteries (spent LIBs). Selective leaching of Li was achieved by carbothermic reduction roasting and leaching with Na2S2O8. After reduction roasting, high-valence TMs were reduced to low-valence metals or metal oxides, and Li was converted to Li2CO3. Then Na2S2O8 solution selectively extracted 94.15% of Li from roasted product with leaching selectivity of more than 99%. At last, TMs were leached with H2SO4 without adding reductant with the leaching efficiency of metals all exceeding 99%. Na2S2O8 added during the leaching process destroyed the agglomerated structure of the roasted product to open the way Li entered the solution. Under the oxidative environment of Na2S2O8 solution, TMs would not be extracted. At the same time, it helped to regulate the phase of TMs and improved the extraction of TMs. Furthermore, the phase transformation mechanism of roasting and leaching was discussed through thermodynamic analysis, XRD, XPS, and SEM-EDS. This process not only realized the selectively comprehensive recycling of valuable metals in spent LIBs cathode materials; but also followed the principle of green chemistry.

Preparation of a novel nano-Fe3O4/triethanolamine/GO composites to enhance Pb2+/Cu2+ ions removal.

In this paper, a magnetic nano-Fe3O4/triethanolamine/GO composite (TEA-GO-FE) was prepared by using graphene oxide (GO), triethanolamine (TEA), and ferric chloride. The result indicates that triethanolamine acted as an important role for the growing of Fe3O4 and adsorption ability of composite material. The synthesis mechanism of TEA-GO-FE was investigated through the medium of SEM-EDS, XRD, FT-IR, and TEM. The characterization results indicated Fe3O4 nanoparticles have been successfully loaded on the surface of graphene oxide and they were encapsulated by TEA and have excellent stability. According to the results of XRD, the general particle size of Fe3O4 on TEA-GO-FE was 27.5 nm. In order to understand the adsorption properties of TEA-GO-FE for Pb2+ and Cu2+, this article uses a static adsorption study method. The optimized adsorption conditions are as follows: pH = 5.0, temperature is 293.15 K, and the ion concentration is 100 mg/L. Under the optimized prerequisites, the adsorption capacities of Pb2+ and Cu2+ were 121.5 mg/g and 68.7 mg/g, separately. Through thermodynamic as well as kinetic studies, the adsorption process of Pb2+ and Cu2+ on TEA-GO-FE is a self-heating process.