Adsorption Properties Of Cd Research Articles

Application of alkaline sludge based LDHs in Cd and Cu polluted wastewater remediation: Process and mechanism

The alkaline sludge produced by the neutralization treatment of acid mine drainage (AMD) is not only large and difficult to treat, but also prone to secondary pollution. The cost of conventional sludge treatment technology is high, so there is an urgent need to develop new methods. The process of neutralizing AMD is similar to the co-precipitation reaction of LDHs, so the cost of recovering LDHs from AMD is lower, but the application performance of LDHs is limited by the stacking of laminates. In this paper, the structure of LDHs was optimized by adding biochar (BC) during the neutralization process of AMD. After adding 40 % BC, the crystal planes of alkaline sludge based LDHs (AS-LDHs) became more parallel, and the adsorption properties of Cd and Cu were increased by 2.7 and 1.95 times, with the maximum adsorption amounts of 901.5 and 231.3 mg/g, respectively. The relevant removal mechanism was investigated in depth at the electronic scale by experiments combined with DFT calculations. Since AS-LDHs have the advantages of good acid stability, low zero-point charge and strong adsorption and regeneration capacity, this method has a broad application prospect.

Magnetic Fe3O4/ZIF-8 optimization by Box-Behnken design and its Cd(II)-adsorption properties and mechanism

In this study, the preparation of magnetic Fe 3 O 4 /ZIF-8 (MFZ) and its adsorption properties for Cd(II) from water were investigated. Various characterizations demonstrate that the as-prepared MFZ has well magnetic-separation performance and thermal stability. In batch adsorption tests, the effects of pH, initial concentration, and adsorbent dosage were evaluated. According to the findings, when the pH is 7 and the dosage is 150 mg/L, the adsorption capacity for a 40 mg/L Cd(II) solution reaches 102.3 mg/g in 180 min. The Cd(II) adsorption processes was found to correspond to pseudo-first-order kinetics and Langmuir model according to the adsorption kinetics and isotherms. The Langmuir model predicted a maximal saturation adsorption capacity of 160.26 mg/g at 298 K. Thermodynamic analysis revealed that the Cd(II) adsorption is an endothermic, spontaneous process. Ion exchange, coordination reaction, and electrostatic interaction are all involved in Cd(II) adsorption by MFZ. The optimum conditions for Cd(II) adsorption were proposed and confirmed in accordance with the results of the response surface optimization experiments. Furthermore, regeneration tests demonstrate the great repeated regeneration ability of MFZ. According to the anticipated production cost, treating wastewater with a Cd(II) concentration of 40 mg/L would cost roughly US$ 8.35/m 3 . MFZ showed good potential for Cd(II) removal from water.

Efficient removal of heavy metal ions from aqueous solution by a novel poly (1-vinylimidazole) chelate resin

Using SI-ATRP technique, 1-vinylimidazole (VI) monomer was directly modified onto the surface of CMPS resin to prepare a chelating resin (PVI-g-PS) with imidazole ring as functional group. The adsorption properties of Cd(II), Ni(II), Pb(II) and Cu(II) were studied. It was found that with the increase in ATRP time and the amount of VIM, the graft ratio of VIM increased linearly, which indicated that the density of imidazole ring on the surface of resin increased. Adsorption experiments showed that the resin has good adsorption properties for Cd(II), Ni(II), Pb(II) and Cu(II). At pH 5.0, the static saturated adsorption amount of PVIM-g-PS for Cd(II), Ni(II), Pb(II) and Cu(II) was 2.82, 1.77, 1.22 and 0.83 mmol g−1, respectively. The adsorption model could be described by Langmuir isothermal adsorption and the adsorption process accorded with quasi-first-order kinetic equation. In addition, the resin has good desorption rate and reusability. These findings suggest that the resin can be potentially applied to the efficient removal of heavy metal ions from wastewater.

Preparation of green chelating fibers and adsorption properties for Cd(II) in aqueous solution

Chitosan chains (CTS) were grafted onto polyvinyl alcohol fibers (PVAf) with the aid of coupling agent γ-glycidoxypropyltrimethoxysilane, producing grafted fibers PVAf-g-CTS. Then, chloroacetic acid (CA) was used to react with the chitosan chains on the PVAf-g-CTS surface via nucleophilic substitution reaction to produce fibrous PVAf-g-CACTS with multiple adsorption sites. The products were characterized by using FTIR, SEM, XRD and XPS, revealing that the reaction followed the S N 2 mechanism. Optimum parameters, including a reaction temperature of 50 °C and a mass ratio of PVAf-g-CTS to CA of 1:0.12, were determined for the reaction. Adsorption experiments confirmed that PVAf-g-CACTS showed greater adsorption characteristics for Cd(II) in aqueous solutions compared with PVAf-g-CTS and PVAf. In particular, the rate of Cd(II) uptake by using PVAf-g-CACTS was higher, and the equilibrium was reached within 80 min. When pH was 7, the saturated adsorption capacity reached 47.65 mg g−1. The adsorption kinetics conformed to the pseudo-second-order model, and the adsorption process was in accordance with the Langmuir and Temkin isotherm model. Adsorption–desorption cycle experiments showed that PVAf-g-CACTS had good performance of reuse, and the adsorption mechanism was analyzed further by using XPS.

Facile synthesis, characterization, and adsorption properties of Cd (II) from aqueous solution using β-cyclodextrin polymer impregnated in functionalized chitosan beads as a novel adsorbent

This study explores the adsorption capacity of carboxymethyl-β-cyclodextrin (CMβ-CD) functionalized chitosan (CS) impregnated with water-insoluble epichlorohydrin cross-linked β-cyclodextrin polymer (β-CDP) to yield CS-β-CDP-CMβ-CD composite beads for the removal of toxic Cd (II) ions from aqueous solutions. Characterization of the adsorbent was performed with XPS, FTIR, NMR, BET and SEM. The synergistic effect was expected and found at removing Cd (II) with a sorption capacity exceeding 378mgg−1 (approximately 3.37mmolg−1), which is higher than any other existing technology. The removal of Cd (II) was found maximum at pH 6.5. The rate reduction can be expressed by pseudo-second-order reaction kinetics. Thermodynamic parameters such as the enthalpy (ΔH0), entropy (ΔS0), and free energy change (ΔG0) suggest the endothermic adsorption of Cd (II) in solution. The activation energy was calculated to be 65.62kJ mol−1 indicating a chemisorption process. The regeneration and reusability of the adsorbent were found suitable for in situ application of this technology for Cd remediation. The Langmuir isotherm model, which is effective for analyzing equilibrium data, indicated both monolayer adsorption and chemisorption. The intraparticle diffusion model indicated both film diffusion and intraparticle diffusion as the rate limiting steps. Thus, the synthesized CS-β-CDP-CMβ-CD beads showed good adsorption selectivity for Cd (II) having excellent regeneration and reusability.

Fast artificial neural network (FANN) modeling of Cd(II) ions removal by valonia resin

In the existing research, firstly, Cd adsorption properties and kinetics were studied on valonia tannin resin (VTR) from aqueous solutions at optimized process parameters such as temperature, pH of solution, initial ion concentration, and contact time. Then, a four-layer fast artificial neural network was constructed and tested to model the equilibrium data of Cd metal ions onto VTR. The properties of the VTR and the experimental conditions were used as inputs to predict the corresponding cadmium uptake at equilibrium conditions. The constructed ANN was also found to be precise in modeling the cadmium adsorption isotherms and kinetics for all inputs during the training process. ANN models were setup with varying numbers of hidden layers and different neuron numbers at each hidden layer as input parameters, mean squared error values were calculated for the train, test, and overtraining caution system status and the proper model according to these values was determined. The obtained simulation results showed that the applied technique of ANN has better adjusted the equilibrium data of the Cd adsorption when compared with the conventional isotherm models.

Preparation of Nano Iron Oxide Coated Activated Sludge Granules and its Adsorption Properties for Cd (II) Ions in Aqueous Solutions

The purpose of this study is Preparation of nano iron oxide coated activated sludge granules and its adsorption properties for Cd (II) ions in aqueous solutions. Activated sludge as biosorbent was modified using nano iron oxide coating and examined for removal of cadmium ions from aqueous solutions. The effect of parameters including amount of coating, contact time, solution pH, initial Cd concentration and adsorbent dosage was evaluated in batch experiments. The results showed that percentage removal of 91.6 was achieved by using modified sludge at alkaline pH 9 and contact time 120 min. The uptake of cadmium was best described by Langmuir-Freundlich isotherms. The kinetic study revealed that Cd (II) adsorption was in agreement with pseudo second-order equation. The Cd (II) loaded and unloaded granules were analyzed using Scanning Electron Microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Based on the obtained results, the modified activated sludge granules with nano iron oxide are an efficient adsorbent for removal of cadmium ions as inorganic water and wastewater pollutant.

Preparation and characterization of nanocomposite, silica aerogel, activated carbon and its adsorption properties for Cd (II) ions from aqueous solution

A novel composite adsorbent, silica aerogel activated carbon was synthesized by sol-gel process at ambient pressure drying method. The composite was characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Nitrogen adsorption/desorption isotherms (BET).In the present study, the mentioned adsorbent was used moderately for the removal of cadmium ions from aqueous solutions and was compared with two other adsorbents of cadmium, activated carbon and silica aerogel. The experiments of Cd adsorption by adsorbents were performed at different initial ion concentrations, pH of the solution, adsorption temperature, adsorbent dosage and contact time. Moreover, the optimum pH for the adsorption was found to be 6.0 with the corresponding adsorbent dosage level of 0.1g at 60°C temperature. Subsequently, the equilibrium was achieved for Cd with 120min of contact time.Consequently, the results show that using this composite adsorbent could remove more than 60% of Cd under optimum experimental conditions. Langmuir and Freundlich isotherm model was applied to analyze the data, in which the adsorption equilibrium data were correlated well with the Freundlich isotherm model and the equilibrium adsorption capacity (qe) was found to be 0.384mg/g in the 3mg/L solution of cadmium.

Synthesis and characterization of a novel amino modified starch and its adsorption properties for Cd(II) ions from aqueous solution

A new amino modified starch (AMS) has been synthesized via grafting polymerization and ring-opening reaction using cassava starch as raw material and used as an adsorbent for the removal of Cd(II) ions from aqueous solution. The adsorbent was characterized by infrared spectroscopy (FT-IR), X-ray diffraction (XRD) patterns, scanning electron microscopy (SEM). Batch adsorption experiments were carried out as a function of pH, adsorption time, initial Cd(II) ions concentration and temperature. Moreover, the equilibrium, thermodynamics and kinetics of the adsorption process were further investigated. It is found that the effect of pH on adsorption is visible and the optimum value is 6–7. The present adsorption system can be described more favorably by the pseudo-second-order kinetic model. The adsorption equilibrium data are correlated well with the Langmuir isotherm model. Furthermore, the adsorption is a spontaneous and endothermic process with increased entropy, and the rise of temperature will benefit the adsorption. In addition, the adsorption–desorption studies show that the AMS adsorbent can be reused almost without any loss in the adsorption capacity over three cycles.

Adsorption properties of Cd(II)-imprinted chitosan resin

A Cd(II)-imprinted chitosan resin (Cd-ICR) was prepared for adsorption of Cd(II) from aqueous solutions. Batch adsorption experiments were performed to evaluate the adsorption conditions, selectivity and reusability as well as its application in the removal of Cd(II) from oyster hydrolysate. The results indicated that the maximum adsorption capacity of Cd-ICR was 0.795 mmol/g in sole Cd(II) solution at pH 5.0, 45 °C with equilibrium time 10 h. The selectivity coefficient of Cd(II) and other metal cations on Cd-ICR indicated an overall preference for Cd(II), which was much higher than that of non-imprinted chitosan resin. Cd-ICR could be reused for ten times with about 27% regeneration loss. FTIR spectra demonstrated that Cd(II) in Cd-ICR occurred on amino and secondary hydroxyl groups. The removal ratio of Cd(II) from oyster hydrolysate was 73.6%, while that of Ca(II) and Zn(II) were 6.2 and 9.9%, respectively. This suggests that Cd-ICR is a very promising adsorbent for selective removal of Cd(II) from aqueous solutions.