Wash water waste pretreatment system

Investigations were completed on wash waters based on each candidate personal cleansing agent. Evaluations of coagulants, antifoam agents, and the effect of promising antifoams on the chemical precipitation were included. Based on these evaluations two candidate soaps as well as their companion antifoam agents were selected for further work. Operating parameters included the effect of soap concentration, ferric chloride concentration, duration of mixing, and pore size of depth filters on the degree of soap removal. The effect of pressure on water flow through filter cartridges and on the rate of decline of water flow was also investigated. The culmination of the program was the recommendation of a pretreatment concept based on chemical precipitation followed by pressure filtration

Efficiency of the Combined Chemical Precipitation -Reduction Process to Remove Dye and Chromium from Industry Wastewater of Home Appliance

Background: Industrial wastewater is one the most important pollutants of environment. This study aimed to evaluate the efficiency of the combined chemical precipitation-reduction process for removal of dye and chromium from wastewater of home appliance factories. Methods: This experimental study was performed in laboratory scale on wastewater from the dying unit of the home appliance factory. The process used was a combination of the chemical precipitation-reduction process. Combine sampling was done and 214 samples were analyzed. COD, dye, and chromium were measured in samples. MgCl2, Polyaluminium Chloride (PAC), and FeCl3, cationic polymer and bentonite were used for chemical precipitation; and sodium meta bi sulfite was used for chemical reduction. Data were analysed by ANOVA and Tukey tests and by SPSS 16 software. Results: The results show that PAC had the highest color removal efficiency (90.92%). Also, the highest COD removal was related to the combination of magnesium chloride (1.4 mg/l), poly aluminum chloride (0.6 mg/l), and the coagulant aid cationic polymer (0.4 mg/l) with an efficiency of 89.11%. Moreover, total efficiency of the combined chemical precipitation and reduction process in chromium removal was 94%. Conclusion: The chemical precipitation- reduction process as a pre-treatment method has high efficiency in removal of COD, dye and chrome from wastewater of home appliance factories

Mössbauer study of nanodimensional nickel ferrite-mechanochemical synthesis and catalytic properties

Iron-nickel spinel oxide NiFe2O4 nanoparticles have been prepared by the combination of chemical precipitation and subsequent mechanical milling. For comparison, their analogue obtained by thermal synthesis is also studied. Phase composition and structural properties of iron-nickel oxides are investigated by X-ray diffraction and Mössbauer spectroscopy. Their catalytic behavior in methanol decomposition to CO and methane is tested. An influence of the preparation method on the reduction and catalytic properties of iron-nickel samples is established

Calcareous concretions in the Levriere (tributary of the Epte, secondary tributary of the Seine, Eure department) [Translation from: Bull.Ass.fr.Etud.Quaternaire 1973(2), 79-87, 1973]

From research carried, out on a section of the Levriere, concretions (granules, nodules, which were sometimes joined together) partly covering the river ”bottom” were observed. The authors propose to make besides a petrographic examination of the calcareous precipitations and to see if their origin is connected to a biological activity, or if it is purely a case of a physical-chemical precipitation. The hydrological background of the Levriere, a small river of the Normandy Vexin, is given and conditions of the formation of the concretions studied

Calcium phosphate bioceramics prepared from wet chemically precipitated powders

In this work calcium phosphates were synthesized by modified wet chemical precipitation route. Contrary to the conventional chemical precipitation route calcium hydroxide was homogenized with planetary mill. Milling calcium oxide and water in planetary ball mill as a first step of synthesis provides a highly dispersed calcium hydroxide suspension. The aim of this work was to study the influence of main processing parameters of wet chemical precipitation synthesis product and to control the morphology, phase and functional group composition and, consequently, thermal stability and microstructure of calcium phosphate bioceramics after thermal treatment. The results showed that it is possible to obtain calcium phosphates with different and reproducible phase compositions after thermal processing (hydroxyapatite [HAp], β-tricalcium phosphate [β-TCP] and HAp/β-TCP) by modified wet-chemical precipitation route. The β-TCP phase content in sintered bioceramics samples is found to be highly dependent on the changes in technological parameters and it can be controlled with ending pH, synthesis temperature and thermal treatment. Pure, crystalline and highly thermally stable (up to 1300°C) HAp bioceramics with homogenous grainy microstructure, grain size up to 200–250 nm and high open porosity can be successfully obtained by powder synthesized at elevated synthesis temperature of 70°C and stabilizing ending pH at 9

Characterization of nanodimensional Ni-Zn ferrite prepared by mechanochemical and thermal methods.

Nickel zinc ferrite nanoparticles, Ni1−xZnxFe2O4 (x = 0, 0.2, 0.5, 0.8, 1.0), with dimensions below 10 nm have been prepared by combining chemical precipitation with high-energy ball milling. For comparison, their analogues obtained by thermal synthesis have also been studied. Mössbauer spectroscopy, X-ray diffraction, and magnetic measurements are used for the characterization of the obtained materials. X-ray diffraction shows that after 3h of mechanical treatment ferrites containing zinc are formed, while 6h of treatment is needed to obtain NiFe2O4. The magnetic properties of the samples exhibit a strong dependence on the phase composition, particle size and preparation method

Chemical Precipitation and Coatings of Tin Selenide

Tin selenide were prepared chemically in alkaline aqueous solution. The crystalline powder was coated onto microscope glass slides using polyvinyl alcohol solution. The coatings were subjected to annealing at various temperatures to study the effect towards the structure, morphology and composition of the material. The product prepared was characterised using various techniques. The photoresponse for the samples were also studied. The photoelectrochemical (PEC) cell configuration was p-SnSe | (0.01 M K4Fe(CN)6¾0.01 M K3Fe(CN)6.3H2O¾0.1 M Na2SO4| Pt)

Technical-economic comparison of chemical precipitation and ion exchange processes for the removal of phosphorus from wastewater

Chemical precipitation with the addition of ferric chloride is commonly used to remove phosphorus from wastewater. However, since its application also involves several disadvantages, alternative solutions are required. The present paper shows the results of a full-scale experimental work aimed at evaluating the efficiency of the ion exchange process using a polymeric anion exchange resin impregnated with aluminum ions in the removal of phosphorus from wastewater. The study compared the results obtained through this process with chemical precipitation, considering both technical and economic issues. At the same dosage of 6 L/hour and influent concentration (about 6 mg/L), total removal efficiency of 95% and 78% (including also that occurring in the mechanical and biological processes) was achieved by means of the anion exchange process and chemical precipitation, respectively. However, in the latter case, this value was insufficient to ensure consistent compliance with the limit of 2 mg/L Ptot set on the effluent; to achieve this goal, the ferric chloride dosage had to be raised to 12 L/hour, thus increasing the related costs. Furthermore, the anion exchange process generated a lower sludge production. Therefore, the ion exchange process represents a valid alternative to chemical precipitation for P removal from wastewater

Recovery of ammonia from wastewater through chemical precipitation

Chemical precipitation is a consolidated technique applied in wastewater treatment to remove and recover phosphorous and ammonium that remain in the effluent after the anaerobic digestion treatment. The precipitate is magnesium ammonium phosphate hexahydrate (MgNH4PO4·6H2O), also known as struvite, and it is sold as a slow-release fertiliser. However, the value of struvite is quite low and has a limited market. Furthermore, it precipitates with heavy metals and other impurities that need to be removed to make the fertiliser commercially viable. This study looked at the thermal decomposition of struvite to recover added value products and recycle the magnesium for further precipitation. A kinetic study was carried out to understand the mechanism of decomposition and the formation of the different solid phases, which is fundamental for the design and optimisation of the technology. The thermogravimetric study confirmed that thermal decomposition is possible, but ammonia could not be completely released below 250 °C. The thermal analysis also led to the determination of the energy required for the decomposition, found to be 1.87 kJ g−1, which also includes the evaporation of water and ammonia. The kinetic study through the isoconversional method showed the presence of two major reactions, and the model-fitting approach identified the diffusion model as the best fit for the first reaction. The activation energy of the first reaction found with this method was 0.24 kJ g−1, comparable with the data obtained from the isoconversional method. The two-stage decomposition reactions were proposed, and the final calcination product was confirmed as magnesium pyrophosphate, which could be used in agriculture or dissolved in diluted mineral acids solution to separate the phosphate from the magnesium