Małgorzata Osińska

COPPER RECOVERY BY THE CEMENTATION METHOD

Abstract Cyanide-free, sulphate-based copper electroplating waste solutions and spent nitric acid solutions from the etching of copper were investigated for copper recovery by cementation. It was found that continuous rotation of pieces of iron together with waste copper sulphate solution or intense circulation of the solution along through motionless iron pieces (e.g. scrap iron) with occasional shaking results in copper recovery of more than 99% within 15–30 min. In the case of copper-laden nitric acid solution before cementation it must be at least 2 fold diluted and sodium pyrosulfite should be added to overcome the oxidizing medium of nitric acid. When the pH of the solution is below 1, it is recommended to increase the pH to 1.5 (by adding NaOH prior to cementation). The postcementation solution treatment comprises pH correction to pH 9 followed by the removal of metal hydroxides by sedimentation or filtration.

Tin recovery from an electroplating sludge

Abstract Tin electroplating from a fluoroborate electrolyte produces sludge containing approximately 50% tin. It can be extracted by leaching the sludge with concentrated hydrochloric acid at room temperature for one month or by boiling in 10% HCl solution for two hours. Electrowinning from H2SnCl6 solution with a steel cathode and graphite anodes permits recovery of tin with 93% efficiency at tin concentrations in the electrolyte exceeding 50 g/l and a current density of 5 A/dm2. The cell is covered with a box with air passing through two washers filled with 15–20% NaOH solution. Chlorine gas evolved at the anodes is adsorbed in washers; sodium hypochlorite, of more than 10% strength in solution, is yielded as a byproduct, with 80% efficiency.

Removal of lead(II), copper(II), cobalt(II) and nickel(II) ions from aqueous solutions using carbon gels

The carbon gel and carbon gel doped with 0.5, 1 and 2 wt% of graphite intercalation compound were used for the removal of heavy metals from aqueous solutions. These materials were prepared by a sol-gel process that involves a polycondensation of resorcinol and formaldehyde. Nitrogen adsorption, scanning electron microscopy, energy dispersive spectroscopy and fourier transform infrared spectroscopy were used for a morpho-structural adsorbent investigation. In the present paper, Cu, Co, Pb and Ni ions adsorption experiments were carried out in batch conditions under magnetic stirring. The effect of some parameters such as contact time, metal ions’ concentration and pH were examined. Adsorption data on all sorbents, followed both the Frendlich and Langmuir models. The data better fitted the Langmuir isotherm than the Frendlich one. The highest degree of removal was achieved for Pb ions at the initial concentration of 10 mg/l and for 2 g/l adsorbent dose. Adsorption results expressed as adsorption capacities showed that carbon gel doped with 2 wt% of graphite intercalation compound is the best adsorbent.Graphical Abstract

Ammonium removal from waste solutions by precipitation of MgNH4PO4 II. Ammonium removal and recovery with recycling of regenerate

Abstract It was found that the ammonium ion removal product MgNH4PO4·6H2O after drying and roasting becomes converted into the regenerate Mg3(PO4)2 suitable for recycling in the ammonium ion removal/recovery process. The gaseous ammonia expelled during roasting can be utilized according to known methods while the regenerate can be used as a source of PO43− and Mg2+ ions in MgNH4PO4·6H2O formation. After adding the regenerate to ammonium-laden waste solution, strong acid (HCl or H3PO4) is introduced to dissolve the regenerate (pH 1–2) and then pH is adjusted with NaOH to 9–10. Stirring is carried out preferably for 24 hours and the precipitated MgNH4PO4·6H2O is separated and returned for recycling. By this method the ammonium ion concentration in treated solutions can be reduced to below 1 mg/l.

Nickel immobilization in ceramic matrix admixed with waste nickel hydroxide

WAXS examinations performed with nickel hydroxide samples heated to various temperatures showed that freshly settled wet nickel hydroxide sample contains some amount of crystalline beta-Ni(OH)(2) structure and its share increased when sample was dried during 3 weeks at ambient temperature. However, the share significantly decreased when the sample was dried at 110 degrees C and more so at 250 degrees C. Crystalline phase traces of Ni(OH)(2) disappeared after sample burning at 980 degrees C and instead the distinct presence of crystalline NiO was determined. The above samples were examined for solubility in stoichiometric amount of sulphuric acid diluted with water to pH 1.9 and 2.8. Solubility was determined by measuring nickel ion concentration in leachate by the AAS method. The dissolving rate was found to decrease with the rise of temperature to which the nickel hydroxide samples were heated. The solubility of Ni(OH)(2) sample burnt at 980 degrees C was undetectable during 90 h solubility-testing time likely due to its transformation into sparingly soluble crystalline NiO. The latter is considered to be the reason for effective immobilization of waste nickel hydroxide in ceramic prepared by blending with clay and sintering at 980 degrees C.

Ammonium removal from waste solutions by precipitation of MgNH4PO4 I. Ammonium removal with use of commercial reagents

Abstract The method of ammonium ion removal from industrial waste solutions was investigated and parameters for MgNH 4 PO 4 precipitation were determined. A solution laden with NH 4 + ions was brought to pH 1–2 by the use of H 3 PO 4 ; MgO was then added and the pH adjusted to 9–10 with the use of NaOH solution. Stirring of the suspension was carried out during a prolonged period of time (⩾ 3 hours), with final filtration or sedimentation. By this method the ammonium ion content in the filtrate may be reduced to concentrations below 1 mg/l. The MgNH 4 PO 4 ·6H 2 O sediment produced is considered to be a long-term fertilizer, suitable for agricultural use.

Ultrafine Pt–Ni bimetallic nanoparticles anchored on reduced graphene oxide nanocomposites for boosting electrochemical detection of dopamine in biological samples

Pt–Ni bimetallic nanoparticles on the surface of reduced graphene oxide (rGO) nanosheets were prepared by using a wet–reflux strategy and characterized by transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), Xray diffraction (XRD) and Raman spectroscopy. The glassy carbon electrode modified with Pt–Ni/rGO demonstrated excellent electrochemical activity towards dopamine (DA) in the presence of acetaminophen (APAP) and etilefrine hydrochloride (ET). From the differential pulse voltammetry (DPV) results obtained for the ternary mixture of DA, APAP and ET, the limit of detection (LOD) and limit of quantification (LOQ) of DA were calculated to be 0.0026 μM and 0.00876 μM, respectively. The proposed sensor was successfully employed for the sensing of DA in aqueous solution, pharmaceutical drugs and human serum samples in a mixture with APAP and ET.