Removal Of Cd Ions Research Articles

Detection and removal of cadmium ion by a neoteric polyethylenimine carbon dots @ lanthanum orthoferrite nanocomposite

In this study, a fluorescent polyethylenimine carbon dots (PEI-CDs) and an adsorbent lanthanum orthoferrite (LaFeO3) are composited as PEI-CDs/LaFeO3 (LFPC), concerning simultaneous detection and removal of cadmium (Cd) ions in the aqueous medium. The fluorescent “Off-On” mechanism is used in detecting cadmium ions and the removal of Cd ions is achieved by the adsorption method. Metal ions selectivity, optimization of the sensor with pH and time, the limit of detection, batch experiments (effect on adsorption by varying pH, initial concentration of metal ions, and adsorbent dosage), and adsorption isotherm studies are carried out in a standardized methodology for effective detection and removal of cadmium ions. The sample's pH is a significant parameter for both detection and removal, here pH 6 is an optimum condition to attain high fluorescent sensitivity and adsorption efficiency. Real sample analysis is performed to check the material's practicability. The synthesized material is characterized by X-ray diffraction, UV‐Vis spectroscopy, photoluminescence spectroscopy, Fourier transform infrared analysis, scanning electron microscopy, high-resolution transmission electron microscopy and energy dispersive X-ray analysis. The lifetime of a fluorophore and zeta potential measurements support the mechanism behind the sensing and the removal of cadmium ions.

Remediation of contaminated sand by Cd ions with variation operation: Batch and flushing column with foam and without foam of SDS surfactant

An anionic surfactant, Sodium dodecyl sulfate (SDS), was applied to remove Cd ions as contaminants on the sand surface. The remediation operation approach was used, such as batch, flushing column without foam, and with foam of SDS solution. Increasing the SDS concentration is possible to improve the removal ability of Cd ions from the sand surface. For batch, the operation performs the higher removal ability by increasing the shaking rotation per minute (rpm). Fluctuation of the percentage removal efficiency (% RE) was shown by using a flushing column without foam at each flow rate variation. The channeling effect during flushing in the column was proved to be the cause of fluctuation in the removal efficiency. Flushing with foam is possible to increase the removal efficiency from 10% by batch and flushing without foam to about 70% with foam. The increasing flow rate of surfactant SDS solution is possible to increase the removal efficiency and flow to the intra-particle area of sand and then decrease the channeling effect. Flushing in column approach with foam by anionic surfactant SDS shows the higher ability and more efficiency in the removal of Cd ions on the sand surface.

Adsorption isotherm, kinetics and response surface methodology optimization of cadmium (Cd) removal from aqueous solution by chitosan biopolymers from cephalopod waste

The present investigation was aimed to explore the cadmium removal efficiency, mechanism and characterization of Chitosan biopolymers from cephalopods waste. The extracted chitosan has showed good yield of 32% and with high minerals, ash and moisture content. In the Fourier-transform infrared spectroscopy (FT-IR) analysis multiple active functional groups of Amine, Amine, Hydroxyl were found between 612 and 3424 cm−1 and the sugar signals such as N-acetyl glucosamine (GlcNAc) and H-1 [GlcN (H-1D), GlcNAc (H-1A)] were identified in Chitosan by 1H Nuclear Magnetic Resonance (NMR). The Crystalline, rough surface, micropores characters were observed in Chitosan surface by Scanning Electron Microscope (SEM) analysis and the pores played a key role in adsorption process. The Cd ions removal was performed by batch experiment and the results were revealed that the pH, temperature, time and dosage highly influenced the process and the optimum condition was discovered through RSM for pH 7, temperature 42.5 °C, time 220 min and dosage of sorbent 1 g/L respectively. The kinetics models of the Cd removal were carried out and the results revealed that the Pseudo-second order is more suitable and fit for removal than Pseudo-first order model. Chitosan surface characters and functional groups played a big role in adsorption process and Chitosan can be alternative eco-friendly, low cost and highly efficient sorbent for heavy metal removal in effluent treatment plants.

Investigation of materials for reactive permeable barrier in removing cadmium and chromium(VI) from aquifer near a solid domestic waste landfill.

The sorption characteristics of raw and biofilm-coated materials: vermiculite, lightweight expanded clay aggregate (LECA), perlite, zeolite, and shungite toward Cd and Cr(VI) ions were investigated to evaluate the possibility of their use as filtration barrier in the aquifer near a solid domestic waste landfill. The effectiveness of Cr(VI) removal by the raw materials changed in the following order: shungite > zeolite > perlite > vermiculite > LECA and for Cd: zeolite > shungite > vermiculite > perlite > LECA. After biofilm formation on the surface of the materials, the sorption capacity increased in some (perlite, LECA), while in others (zeolite) it was reduced. Four kinetic models were used to describe the experimental data. Mechanisms of metal removal were proposed: for Cr(VI), a characteristic combination of sorption processes was suggested, while the removal of Cd ions could occur by ion exchange and by complexation on the surface of the sorbent. Cr(VI) reduction by living bacterial cells forming a biofilm on the sorbent surface was assessed.

Selectivity and efficient Pb and Cd ions removal by magnetic MFe2O4 (M=Co, Ni, Cu and Zn) nanoparticles

Spinel ferrite MFe2O4, (M = Co, Ni, Cu and Zn) nanoparticles (NPs) were prepared by microwave combustion method using metal nitrates as precursors, in addition to urea as fuel. Rietveld analysis of X-ray diffraction patterns indicates the formation of single phase for NiFe2O4 and ZnFe2O4, while (α-Fe2O3 and CuO) phases precipitate for CoFe2O4 and CuFe2O4, respectively. After annealing 800 °C for 16 h, single cubic CuFe2O4 phase is obtained. SEM images show spherical/undefined shaped particles at the nanoscale with broad particle size distribution and high level of agglomeration. Magnetisation-field (M-H) curves reveal ferromagnetic behaviour for CoFe2O4, NiFe2O4 and CuFe2O4, and superparamagnetic behaviour for ZnFe2O4. Interestingly, after annealing CuFe2O4 shows a superparamagnetic behaviour due phase tetragonal-cubic phase transformation. Saturation magnetization, remanence and coercivity slightly change after annealing, except for CuFe2O4, due to phase transformation from tetragonal to cubic; Ms decreases abruptly from 25.97 to 1.685 emu/g. The as-obtained spinel ferrite nanopowders are tested for two toxic metal ions removal from aqueous solutions; Cadmium (Cd2+) and lead (Pb2+) with different concentration (5, 10, 20 and 30 mg) and pH (2, 12). The maximum adsorption capacities are found at the lowest concentration (5 mg) and at alkaline medium (pH 12). The as-prepared magnetic nanoparticles demonstrate enhanced efficiency for both Cd2+ and Pb2+, with maximum adsorption capacity of 69.4 and 47.1 mg/g, respectively. Interestingly, the nature of metal M has a direct influence on selectivity, CoFe2O4 toward Cd2+ while ZnFe2O4 toward Pb2+.

Studies on the removal of Cd ions by gastrointestinal lactobacilli.

Accumulation of toxic metal ions in food and water is nowadays a growing health-related problem. One detoxification method involves the use of microorganisms naturally inhabiting the gastrointestinal tract (GIT). The purpose of this study was to prove that lactic acid bacteria derived from the GIT are able to effectively remove Cd2+ from water solution. Seven strains of lactobacilli, out of 11 examined, showed tolerance to high concentrations of cadmium ions. The metal-removal efficiencies of these seven lactobacilli ranged from 6 to 138.4μg/hmg. Among these bacteria, Lactobacillus gallinarum and Lactobacillus crispatus belonged to the highest (85%) Cd-removal efficiency class. An analysis of the zeta potential (ζ) indicated that the bacterial cell surface had a negative charge at the pH ranging from 3 to 10. The presence of carboxyl, amide, and phosphate groups was favorable for Cd2+ binding to the cell surface, which found confirmation in FTIR-ATR spectra. Elemental SEM/EDS analysis and TEM imaging not only confirmed the adsorption of Cd2+ on the cell envelope but also gave us a reason to suppose that Lb. crispatus accumulates metal ions inside the cell. Our findings open perspectives for further research on the new biological function of GIT lactobacilli as natural biosorbents.

Cadmium adsorption on hydrous aluminium (III) oxide: effect of adsorbed polyelectrolyte

Freshly precipitated hydrous oxides of Al (flocs) are important sorbents of heavy metal ions and are used in water treatment processes. The addition of chelating agents or polyelectrolytes can increase the efficiency of heavy metal removal by flocs. The polymer polyethylenimine is commonly used as a flocculant aid in water treatment and has been modified with phthalic acid. Adsorption studies have shown that the addition of millimolar concentrations of polyelectrolyte increases the removal of Cd ions from a 29.7 μM aqueous solution by aluminium flocs from ca. 40% to up to 75%. Experiments in which the pH was varied demonstrated that the observed enhancement of Cd adsorption is caused by a shift of the pH edge to lower pH values in the presence of polyelectrolyte. Maximum polyelectrolyte adsorption occurs between pH 6 and pH 7, corresponding to the point of enhanced Cd adsorption in the presence of polyelectrolyte. The enhancement of Cd adsorption observed below pH 7 is therefore likely to be due to the formation of a ternary surface complex. At pH values above pH 8 the polyelectrolyte forms a stable complex with Cd and Al ions in solution causing floc dissolution and decreased Cd adsorption.

Removal of Cd ions by sol-gel silica doped with 1-(2-pyridylazo)-2-naphthol

1-(2-Pyridylazo)-2-Naphthol (PAN) doped sol-gel silica has been investigated for removal of metal ions from aqueous media. In the doped sol-gel silica, the large reagent molecules are entrapped inside the pores while small metal ions can diffuse into the pores where they are complexed by the reagent and retained inside the pores. This new solid sorbent was applied for removal of Cd(II) from aqueous solutions. The kinetics, adsorption isotherm, equilibration time and pH effect on the removal were studied to optimize the conditions to be utilized on a large scale. It was observed that a sol gel loaded with 0.09 mmol PAN/g, had a capacity of 0.044 mmol Cd/g. The desorption of metal ions was carried by 1 M HCl and the sol-gel silica sorbent could be regenerated and reused repeatedly.