Studies on the purification of wastewaters with high nickel ions content

The paper presents studies on the removal of nickel from wastewaters with high nickel ions content resulting from galvanizing process. In the first step of the purification process, nickel ions were precipitated using a 10 M NaOH solution as precipitation agent. By increasing the pH of the Ni2+ solutions up to 11, the residual concentration of nickel ions reached the values required for the discharge in sewerage and in water resources. Taking into account that this pH value does not allow the discharge, the solution resulting from the precipitation process at pH 9 was submitted in the second step to an advanced treatment using as adsorbent material an Amberlite XAD-4 resin impregnated with di-2(ethyl-hexyl) phosphoric acid. To establish the conditions for the adsorption process was studied the influence of contact time and of adsorbent dosage on the efficiency of nickel ions removal from the solution. The maximum efficiency of ~ 94% was reached after 90 min for an adsorbent dosage of 0.3 g:25 mL. The residual concentration of nickel ions was ~0.5 mg/L, value that allows the discharge in the sewerage and even in water resources

Studies regarding the turning to account of the waste resulting from coal exploitation

In this paper was studied the possibility of turning to account of the waste resulting from coal mining. One way was to use the waste in order to stabilize ash dumps. The chemical analysis of the coal waste and ash showed that both have high zinc and nickel content. As remediation method was chosen for this study the cultivation of barley as bio-indicator plant on substrates obtained by mixing the coal waste and ash in various proportions. After bio-remediation, the zinc content of the substrates fell under the maximum permitted value for all coal-ash mixtures. The nickel content decreased very much, but remained somewhat higher than the maximum permitted value. Another way was to use waste material as adsorbent in view of removal of organic dyes from wastewaters resulting from inkjet cartridge remanufacturing. The coal waste was used in various dosages (S:L = 0.1 g:25 mL; 0.2:25; 0.3:25; 0.4:25 and 0.5:25) and the suspensions were shaken for various contact times (15, 30, 45, 60 and 120 min). The highest removal efficiency ( -60%) was reached for a S:L ratio of 0.5:25 after a 60 min contact time

Studies on column adsorption of arsenic (V) from a real water on dehpa-impregnated XAD-8 resin

Arsenic contamination of drinking water is a widespread problem of international interest. Arsenic is released from the soil through natural processes or due to human activities. In the paper was studied the possibility of removal of arsenic from drinking water using a column filled with Amberlite XAD-8 resin impregnated with di-(2-ethylhexyl) phosphoric acid (DEHPA). The efficiency of arsenic removal from water was established by studying the dependence of arsenic residual concentration and arsenic removal degree on the volume of the water passed over the adsorbent material. The adsorption process had an efficiency of -90% and the arsenic residual concentration was smaller than 10 pg/L. The studies concerning the influence of other ions present in water (Na+, K+, Ca2+, Mg2+, Fen+, Mnn+, NO2", N H /, NO3', PO43', CF) showed that these ions do not interfere with arsenic adsorption process

Use of impregnated resins as adsorbents in view of heavy metals removal from aqueous solutions

The presence of heavy metal ions in environment is a major concern because of their toxicity to many life forms. Heavy metal ions can be removal from water by adsorption on solid support. In the present work, we tested the adsorption of metal ions on solvent impregnated resin (SIR). Di-(2-ethylhexyl)-phosphoric acid (D2EHPA) has been chosen as an extractant for the purpose of this study. The interaction between XAD4 resin and D2EHPA was evaluated by physico-chemical methods of analysis (EDX and SEM). The experimental studies on adsorption of metal ions were carried out on Pb2+, Cu2+, Cd2+, Cr3+, Ni , Fe3+, Zn2+ and Ca2+. A separation method was developed for metals ions and was investigated the influence of contact time on the residual concentration of metal ions, on their removal efficiency and on the adsorption capacity of resin towards metal ions

Magnesium silicate functionalized with sodium-β-glycerophosphate used for Sr(II), Cs(I), Tl(I) adsorption

In this research Sr(II), Cs(I), Tl(I) were removed through adsorption using a functionalized solid support, magnesium silicate with sodium-β-glycerophosphate. The influence of the initial concentration of metal in the solution and of the contact time were investigated. The adsorption process runs quickly obtaining the highest adsorption capacity for Sr(I) 7 mg/g

As(V) adsorption using MFe2O4 (M=Cd2+, Ni2+) ferrite nanoparticles

The paper present the possibilities of arsenic removal from aqueous solutions using as adsorbent MFe2O4 (M=Cd2+, Ni2+) ferrite nanoparticles due to the affinity of arsenic towards iron ions. The ferrites were obtained after a heating treatment of the cadmium respectively nickel ferrioxalate coordination compounds, as precursors, at 500oC. From the two studied adsorbent material the nickel ferrite developed a higher maximum adsorption capacity (132 µg As(V)/g of ferrite) than the cadmium ferrite (109 µg As(V)/g of ferrite) in the removal process of As(V) from aqueous solutions. In both cases the equilibrium between the adsorbent and adsorbate was achieved in 60 minutes

Silica-Coated Magnetic Nanocomposites for Pb2+ Removal from Aqueous Solution

Magnetic iron oxide-silica shell nanocomposites with different iron oxide/silica ratio were synthesized and structurally characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), small-angle neutron scattering, magnetic and N2-sorption studies. The composite that resulted with the best properties in terms of contact surface area and saturation of magnetization was selected for Pb2+ adsorption studies from aqueous media. The material presented good absorption capacit (maximum adsorption capacity 14.9 mg·g−1) comparable with similar materials presented in literature. Its chemico-physical stability and adsorption capacity recommend the nanocomposite as a cheap adsorbent material for lead

Comparison of structure and adsorption properties of mesoporous silica functionalized with aminopropyl groups by the co-condensation and the post grafting methods

The adsorptive potential has been evaluated for the aminopropyl functionalized mesoporous silica materials obtained by co-condensation and post grafting methods. Nitrogen sorption, small angle neutron and X-ray scattering (SANS and SAXS) demonstrated high surface area and well-ordered hexagonal pore structure suitable for applications as adsorbents of metals from waste waters. A comparison of Cr(VI) adsorption properties of the materials prepared by different functionalization methods has been performed. The obtained results demonstrated the adsorption capacity due to the affinity of the chromium ions to the amino groups, and showed that co-condensation of tetraethoxysilane (TEOS) and 3-aminopropyl triethoxysilane (APTES) resulted in higher metal sorption capacity of the materials compared to post-synthesis grafting of aminopropyl groups onto the mesoporous silica particles

Ordered Mesoporous Silica Prepared in Different Solvent Conditions: Application for Cu(II) and Pb(II) Adsorption

In this work, the synthesis of ordered mesoporous silica of MCM-41 type was investigated aimed at improving its morphology by varying the synthesis conditions in a one-pot process, employing different temperatures and solvent conditions. 2-methoxyethanol was used as co-solvent to ethanol. The co-solvent ratio and the synthesis temperature were varied. The pore morphology of the materials was characterized by nitrogen porosimetry and small angle neutron scattering (SANS), and the particle morphology by transmission electron microscopy (TEM) and ultra-small angle neutron scattering (USANS). The thermal behavior was investigated by simultaneous thermogravimetry-differential scanning calorimetry (TG-DSC) measurements. The SANS and N(2) sorption results demonstrated that a well-ordered mesoporous structure was obtained at all conditions in the synthesis at room temperature. Addition of methoxyethanol led to an increase of the pore wall thickness. Simultaneously, an increase of methoxyethanol content led to lowering of the mean particle size from 300 to 230 nm, according to the ultra-small angle scattering data. The ordered porosity and high specific surfaces make these materials suitable for applications such as adsorbents in environmental remediation. Batch adsorption measurements of metal ion removal from aqueous solutions of Cu(II) and Pb(II) showed that the materials exhibit dominantly monolayer surface adsorption characteristics. The adsorption capacities were 9.7 mg/g for Cu(II) and 18.8 mg/g for Pb(II) at pH 5, making these materials competitive in performance to various composite materials

Cs+ Removal from Aqueous Solutions through Adsorption onto Florisil® Impregnated with Trihexyl(tetradecyl)phosphonium Chloride

This research determined the adsorption performance of Florisil® impregnated with trihexyl(tetradecyl)phosphonium chloride (Cyphos IL-101) in the process of Cs+ removal from aqueous solutions. The obtained Florisil® impregnated with the studied ionic liquid was characterized through energy dispersive X-ray analysis and Fourier transform infrared spectroscopy in order to verify that the impregnation with the ionic liquid had occurred. The adsorption process has been investigated as a function of pH, solid:liquid ratio, adsorbate concentration, contact time and temperature. The isotherm data was well described by a Langmuir isotherm model. The maximum adsorption capacities of the Florisil® impregnated with the studied ionic liquid was found to be 3.086 mg Cs+/g of adsorbent. The results indicated that the adsorption fitted well with the pseudo-second order kinetic model