A new method of electrochemical formation of free-standing 3D structures based on the injection of additives that controls the deposition rate was demonstrated using copper-chloride-polyethylene glycol as an example. A densely-packed defect-free pillar was formed upon the injection of chloride-free electrolyte into a chloride-containing electrolyte, where copper deposition was fully suppressed. The effects of diffusion coefficient, injection rate and the distance between injection nozzle and pillar top were evaluated with numerical simulation. A fast diffusion species, a moderate injection rate and a small gap between injection and pillar were found beneficial to obtaining the best contrast in the growth rates between pillar and background. The demonstration of free-standing copper structure in this paper provides an alternative path for electrochemical 3D printing of various metallic materials. Free-standing metallic structures are of interest for various devices. The recently developed additive manufacturing enables the direct formation of such structures without the need of expensive lithography processes.1 Among them, the metal wire feed process 2 was directly adapted from the original extrusion version of polymer 3D printing. 3-5 Extrusion and sintering of metal paste 6 also allow the formation of metal structures. Selective laser melting or sintering [7][8][9] of metal particles can create free-standing or non-attached metallic structures embedded in metal powders.While most of the above processes were heat-based physical processes, chemical reaction based 3D printing processes have been developed typically for direct formation of smaller structures. Tip based electrochemical machining has been widely used in the past to subtractively machine metallic or non-metallic structures for microdevices.10,11 However, electrochemical deposition processes have not been used until more recently for additive formation of 3D metal [12][13][14][15] and conductive polymer [16][17][18] micro-structures. Metal electrodeposition typically involves the reduction of metal ions into metal atoms on a conductive substrate. Therefore, 3D electrodeposition methods taking advantage of a local electrical field, local metal ion or local conductive substrate have been developed. The traditional lithography based electroforming, for example, the through-mask plating and LIGA process are based on the local exposure of conductive substrate. 19 This through mask concept has also been extended to achieve direct formation of nanostructures through local deposition. [20][21][22] Another so-called local electrochemical deposition was invented relying on a locally positioned anode.12-14 Such an anode is typically surrounded by a large insulating material and is closely positioned in a vicinity of the cathode substrate, 23-26 creating a highly local electrical field that enables the deposition to occur only at the location closest to the anode. Recently, Hirt et al. 27 used a modified atomic force microscope tip with fluidic channel to introduc...
Background & Aims of the Study: Heavy metals are the most important and main pollutants because of their accumulation and high toxicity even at very low dose and cause serious hazards to ecological system as well as human health. Thus, their removal has been challenged from drinking water and industrial waters with different technologies. The purpose of this work is to investigate the removal of Cr(VI) from aqueous solutions. Materials & Methods: NiFe 2 O 4 nanoparticles was prepared by the co-precipitation method and then applied for adsorption of Cr(VI) ions from water. Characterization of nanoparticles was carried out via TEM, EDX, XRD and BET analysis. Various physicochemical parameters like the effect of contact time, pH and adsorbent dose were studied, using batch process to optimize conditions for maximum adsorption. Results: The results demonstrated that the size of the NiFe 2 O 4 nanoparticles was about 12 nm and had selectivity for Cr(VI) adsorption. Also, adsorption process was found to be fast with equilibrium time of 55 min. Optimum pH was found to be 3. Maximum adsorption capacity (q m ) as calculated from Langmuir isotherm was found to be 294.1 mg g -1 . Analysis of adsorption kinetics indicated better applicability of pseudo-second-order kinetic model. Conclusions:The results of this study represented that the synthesized NiFe 2 O 4 nanoparticles could be useful for the simultaneous removal of anionic ions from wastewaters.
Background: Among different pollutants released into the environment, dyes are considered as one of the most dangerous contaminants. In recent years, magnetic nanomaterials have attracted much attention for their dye removal capacity. The aim of this study was to explore the adsorption kinetics of an anionic dye (Reactive Orange 13 (RO)) by NiFe2O4 nanoparticles (NiFe2O4 NPs) under various conditions. Methods: NiFe2O4 nanoparticles (NiFe2O4 NPs) were prepared and characterized by X-ray diffraction (XRD), transmission electronic microscopy (TEM), pHpzc and BET methods. The adsorption characteristics of the NiFe2O4 NPs adsorbent were examined using Reactive Orange 13 as an adsorbate. The influences of parameters including pH, dose of adsorbent and contact time were investigated to find the optimum adsorption conditions. Results: Decreasing solution pH and increasing contact time were favorable for improving adsorption efficiency. The kinetic and isotherm data of RO adsorption on NiFe2O4 NPs were well fitted by pseudo-second-order and Langmuir models, respectively. Conclusion: The maximal adsorption capacity of RO was 243.9 mg g-1 at 25◦C and pH 3.0 and the adsorption of RO on the NiFe2O4 NPs follows a monolayer coverage model. NiFe2O4 NPs might be an effective and potential adsorbent for removing anionic dyes from aqueous solutions.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.