Effect of competing ions and causticization on the ammonia adsorption by a novel poly ligand exchanger (PLE) ammonia adsorption reagent

Novel development of zinc oxide-coated carbon nanoparticles from pineapple leaves using sol gel method for optimal adsorption of Cu2+ and reuse in latent fingerprint application

This study underlines a latest approach of preparing nitrogen carbon nanoparticles fused on zinc oxide nanoparticle nanocomposite (N-CNPs/ZnONP nanocomposite) for the uptake of copper ions (Cu2+) from wastewater using a sol gel method. The metal loaded adsorbent was then applied in the latent fingerprint application. N-CNPs/ZnONP nanocomposite proved to be a good sorbent for the optimal adsorption of Cu2+ at pH 8 and 1.0 g/L dosage. Langmuir isotherm best fitted the process with the maximum adsorption capacity of 285.71 mg/g that was superior to most values reported in other studies for the removal of Cu2+. At 25 °C, the adsorption was spontaneous and endothermic. Furthermore, Cu2+-N-CNPs/ZnONP nanocomposite revealed to be sensitive and selective for latent fingerprint (LFP) identification on a variety of porous surfaces. As a result, it is an excellent identifying chemical for latent fingerprint recognition in forensic science.

Selective removal of ammonia from wastewater using Cu(II)-loaded Amberlite IR-120 resin and its catalytic application for removal of dyes

Cationic ligand exchange is one of the most predominant mechanisms for the removal of ammonia from wastewater through complex formation. The complexation technique occurs between the metal ions loaded on the surface of Amberlite IR-120 and ammonia which is present in the medium. Cu(II)-loaded Amberlite IR-120 (R-Cu2+) was prepared and described using FT-IR, TGA, SEM, and EDX techniques. The prepared R-Cu2+ was applied for the elimination of ammonia from an aqueous solution. Different cations such as Co2+ and Ni2+ were loaded onto Amberlite IR-120 to study the impact of counter cation on the removal efficiency of ammonia. The ammonia removal percentage followed the order; R-Cu2+  > R-Ni2+  > R-Co2+. The effects of contact time, pH, initial concentration, temperature, and coexisting ions on the removal of ammonia from wastewater by R-Cu2+ were investigated. The equilibrium adsorbed amount of ammonia was found to be 200 mg/g at pH = 8.6 and 303 K within 60 min using 0.1 g R-Cu2+ and an initial concentration of ammonia of 1060 mg/L. The removal of ammonia using R-Cu2+ obeyed the non-linear plot of both Freundlich and Langmuir isotherms. According to the thermodynamic parameters, the adsorption of ammonia onto R-Cu2+ was an endothermic and spontaneous process. The time-adsorption data followed the pseudo-second-order and intraparticle diffusion models. Moreover, the resulting product (R-Cu(II)-amine composite) from the adsorption process exhibited high catalytic activity and could be low-cost material for the elimination of dyes such as aniline blue (AB), methyl green (MG), and methyl violet 2B (MV2B) from wastewater.

Resin-Mediated pH Control of Metal-Loaded Ligand Exchangers for Selective Nitrogen Recovery from Wastewaters

Highly selective separation materials that recover total ammonia nitrogen (i.e., ammonia plus ammonium, or TAN) from wastewaters as a pure product can supplement energy-intensive ammonia production and incentivize pollution mitigation. We recently demonstrated that commercial acrylate cation exchange polymer resins loaded with transition metal cations, or metal-loaded ligand exchangers, can recover TAN from wastewater with high selectivity (TAN/K+ equilibrium selectivity of 10.1) via metal-ammine bond formation. However, the TAN adsorption efficiency required further improvement (35%), and the optimal concentration and pH ranges were limited by both low ammonia fractions and an insufficiently strong resin carboxylate-metal bond that caused metal elution. To overcome these deficiencies, we used a zinc-acrylate ligand exchange resin and a tertiary amine acrylic weak base resin (pH buffer resin) together to achieve resin-mediated pH control for optimal adsorption conditions. The high buffer capacity around pH 9 facilitated gains in the adsorbed TAN per ligand resin mass that enhanced the TAN adsorption efficiency to greater than 90%, and constrained zinc elution (below 0.01% up to 1 M TAN) because of decreased ammonia competition for zinc-carboxylate bonds. During TAN recovery, resin-mediated pH buffering facilitated recovery of greater than 99% of adsorbed TAN with 0.2% zinc elution, holding the pH low enough to favor ammonium but high enough to prevent carboxylate protonation. For selective ion separation, solid phase buffers outperform aqueous buffers because the initial solution pH, the buffering capacity, and the ion purity can be independently controlled. Finally, because preserving the resin-zinc bond is crucial to sustained ligand exchange performance, the properties of an ideal ligand resin functional group were investigated to improve the properties beyond those of carboxylate. Ultimately, ligand exchange adsorbents combined with solid pH buffers can advance the selective recovery of nitrogen and potentially other solutes from wastewaters.

Experiment and multicomponent model based analysis on the effect of flow rate and nitrate concentration on denitrification in low-permeability media

To better understand the combined effects of flow rate and NO₃^- concentration on denitrification rate and NO₃^- removal efficiency in the low-permeability media, a set of column experiments with different flow rates and injected NO₃^- concentrations were conducted. Denitrification processes under these different conditions were simulated using the PHREEQC code that couples the biogeochemical reactions and hydrological transport processes. In these reactive transport models, Monod kinetics were applied to describe the denitrification process. It was found that, among the experiments conducted in this study, the low flow rate (0.023 m/d) resulted in the low denitrification rate but high NO₃^- removal efficiency. Meanwhile, NO₃^- removal efficiency was the highest (85%) under moderate NO₃^- concentration of 1.29 mmol/L, although denitrification rate increased in response to the increase of NO₃^- concentration. The model results also indicated that NO₃^- removal efficiency of 97% can be achieved with relatively low flow rate and high influent NO₃^- concentration. The results in this study provide insights into NO₃^- remediation, and the temporal and spatial flow rate, as well as NO₃^- concentration distribution, should be pre-evaluated for the effective removal strategies.

Selective Recovery of Ammonia Nitrogen from Wastewaters with Transition Metal-Loaded Polymeric Cation Exchange Adsorbents

Extracting valuable products from wastewaters with nitrogen-selective adsorbents can offset energy-intensive ammonia production, rebalance the nitrogen cycle, and incentivize environmental remediation. Separating nitrogen (N) as ammonium from other wastewater cations (e.g., K⁺ , Ca²⁺ ) presents a major challenge to N removal from wastewater and N recovery as high-purity products. High selectivity and capacity were achieved through ligand exchange of ammonia with ammine-complexing transition metals loaded onto polymeric cation exchange resins. Compared to commercial resins, metal-ligand exchange adsorbents exhibited higher ammonia removal capacity (8 mequiv g^-1 ) and selectivity (N/K⁺ equilibrium selectivity of 10.1) in binary equimolar solutions. Considering optimal ammonia concentrations (200-300 mequiv L^-1 ) and pH (9-10) for metal-ligand exchange, hydrolyzed urine was identified as a promising candidate for selective TAN recovery. However, divalent cation exchange increased transition metal elution and reduced ammonia adsorption. Ultimately, metal-ligand exchange adsorbents can advance nitrogen-selective separations from wastewaters.

Removal of ammonia-nitrogen in wastewater using a novel poly ligand exchanger-Zn(II)-loaded chelating resin

In this study, a novel poly ligand exchanger-Zn(II)-loaded resin was designed to effectively remove ammonia-nitrogen (NH₃-N) from wastewater. The surface morphology and structure of the Zn-loaded resin were characterized using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR), respectively. SEM shows the surfaces of the Zn(II)-loaded resin were rough and nonporous and EDS demonstrated that Zn²⁺ was loaded onto the resin successfully. In addition, the combination form of Zn(II) with NH₃-N adsorption reagent was revealed by FTIR spectra; the complex could be R-N-R-O-Zn-O-R-N-R and R-N-R-(O-Zn)₂. The kinetics and equilibrium of the NH₃-N adsorption onto the Zn(II)-loaded resin has been investigated. The effects of pH, reaction time, and temperature on NH₃-N removal from wastewater by Zn(II)-loaded resin were investigated, and the results showed that the maximum adsorption capacity reached 38.55 mg/g at pH 9.54 at 298 K in 240 min. The adsorption ability of the modified resin decreased with an increase in temperature. Moreover, the NH₃-N adsorption followed a pseudo-second-order kinetic process. The kinetic data demonstrated that the adsorption process might be limited by a variety of mechanisms. The study can provide the scientific foundation for the extensive application of a novel poly ligand exchanger-Zn(II)-loaded resin to remove NH₃-N from wastewater.

Comparative study on the synthesis of magnetic ferrite adsorbent for the removal of Cd(II) from wastewater

The magnetic ferrites were synthesized at ambient temperature through the precipitation method in aqueous solution at varying pH values and were used as novel adsorbents for heavy metal-containing wastewater treatment. The magnetic ferrites were applied for the removal of Cd(II) ion from wastewater. The synthesized magnetic ferrites were characterized by settling velocity, X-ray diffraction, scanning electron microscopy, laser particles size analyzer, and vibrating sample magnetometer. The effects of pH value and contact time on the adsorption process were investigated. The magnetic ferrites had a saturation magnetization value of 82.30 emu/g and a settling velocity of 2%, indicating easy separation from aqueous solution under magnetic field. The adsorption of Cd(II) onto the magnetic ferrites followed the pseudo-second-order kinetics and the Langmuir isotherm model. The most suitable pH condition for the synthesis of magnetic ferrite with optimal Cd(II) adsorption capacity was 9.0, and a maximum adsorption capacity of 160.91 mg/g for Cd(II) ions can be achieved. Based on the cost analysis, the magnetic ferrite was a cost-effective adsorbent for Cd-containing wastewater treatment.