The COD removal efficiency from an instant coffee processing wastewater using electrocoagulation was investigated. For this purpose, the response surface methodology was employed, using central composing design to optimize three of the most important operating variables, i.e., electrolysis time, current density and initial pH. The results based upon statistical analysis showed that the quadratic models for COD removal were significant at very low probability value (<0.0001) and high coefficient of determination (R2 = 0.9621) value. The statistical results also indicated that all the three variables and the interaction between initial pH and electrolysis time were significant on COD abatement. The maximum predicted COD removal using the response function reached 93.3% with electrolysis time of 10 min, current density of 108.3 A/m2 and initial pH of 7.0, respectively. The removal efficiency value was agreed well with the experimental value of COD removal (90.4%) under the optimum conditions.
The optimization of low-magnesium zinc concentrate production process
In this paper the result of the study on chemical leaching of zinc concentrate with H2SO4 solution was presented. The object of this work was to assess the effect of some parameters such as acid concentration, the leaching agent amount /stoichiometry amount or excess of acid were applied/, reaction time and temperature on the process. The investigation was performed as a active experiment according to Hartley's plan. The process optimisation procedure was based on the fuzzy logic system. Mainly, the parameters such as magnesium leaching efficiency and zinc losses were taken into account. It was stated that the highest magnesium leaching efficiency of 77.8% with low Zn-losses was reached when H2SO4 solution concentration was 2.5% for 20%-excess of acid, at temperature 25°C and process time of 1 hour.
Single-walled carbon nanotubes fractionation via electrophoresis
This work presents the influence of the sonication time on the efficiency of the metallic/semiconducting (M/S) fractionation of diazonium salt functionalized single-walled carbon nanotubes (SWCNTs) via free solution electrophoresis (FSE) method. The SWCNTs synthesized via laser ablation were purified from amorphous carbon and catalyst particles through high vacuum annealing and subsequent refluxing processes in aqua regia solutions, respectively. The purified material was divided into two batches. The SWCNTs samples were dispersed in 1% SDS solution in ultrasound bath for 2 and 12 hours. Both dispersed SWCNTs samples were functionalized with p-aminobenzoic acid diazonium salt and fractionated via free solution electrophoresis method. Afterwards, the fractionated samples were recovered, purified from surfactant/functionalities by annealing and investigated via UV-Vis-NIR optical absorption spectroscopy (OAS). The efficiency of the fractionation process was estimated through the comparison of the van Hove singularities (vHS) presented in the obtained fractions to the starting SWCNTs.
This paper presents the results of study on structural parameters (particle size, surface area, pore volume) and the sorption ability of mechanically and thermally activated sodium bicarbonate. The sorption ability of the modified sorbent was evaluated by: partial and overall SO2 removal efficiency, conversion rate, normalized stoichiometric ratio (NSR). Sodium bicarbonate was mechanically activated by various grinding techniques, using three types of mills: fluid bed opposed jet mill, fine impact mill and electromagnetic mill, differing in grinding technology. Grounded sorbent was thermally activated, what caused a significant development of surface area. During the studies of SO2 sorption, a model gas with a temperature of 300°C, of composition: sulfur dioxide at a concentration of 6292 mg/mn3, oxygen, carbon dioxide and nitrogen as a carrier gas, was used. The best development of surface area and the highest SO2 removal efficiency was obtained for the sorbent treated by electromagnetic grinding, with simultaneous high conversion rate.
This paper presents investigation on removal of low molecular organic acids (acetic, lactic, succinic and fumaric) from aqueous solutions with reactive extraction. The results specifically show that the extraction efficiency of acids depends on the type of extractant, diluents of the organic phase and the initial pH of the aqueous phase. It is possible to separate succinic or fumaric from lactic and acetic acids with high selectivity with the use of TOA and Aliquat 336, respectively. Increasing the pH of the aqueous phase results in a reduction of fumaric acid extraction efficiency with solvating extractants. This can be explained by the decreasing share of acidic form, whose extraction is favored by these extractants. Efficient extraction of both fumaric acid and fumarate using Aliquat 336 can be explained by the ionic structure of the quaternary ammonium salt, capable of transporting both forms of the acid.
In this present work, vinasse, a by-product of sugarcane industry, was examined using combined treatment methods to purify it. Electrocoagulation/flocculation, ultrafiltration were applied as pre-treatment and post-treatment, respectively. The effectiveness of combined process was evaluated based on colour, turbidity and chemical oxygen demand (COD) removal. The efficiency of electrochemical reactor was investigated according to process variables such as retention time, electrode distance and electrolyte dose. From the results, the price to treat unit vinasse is found to be 2.5 US$/m3 under optimum conditions. FT-IR analysis of sludge obtained shows the results of electro-coagulation process. Ultrafiltration as post treatment experiments showed the enhanced removal efficiency of colour (91%), turbidity (88%) and COD (85%). The results showed that electrocoagulation followed by ultrafiltration is a suitable combined technique to reduce the colour, turbidity and COD from vinasse liquid.
The influence of leaching solution pH and addition of peroxide hydrogen on the recovery of some components from the used vanadium catalyst with urea solutions
The research was conducted to determine the influence of the pH of the leaching solutions and hydrogen peroxide addition on the efficiency of the recovery of vanadium, potassium and iron compounds from the used vanadium catalyst from the node of oxidation of sulfur dioxide to sulfur trioxide.
The selective hydrogenation of cinnamaldehyde has been studied using palladium catalysts based on epoxy resin cured with ionic liquids. Characterization of palladium catalysts has involved the following methods: IR spectroscopy, X-ray photoelectron spectroscopy (XPS), AAS spectroscopy and time-of-flight secondary ion mass spectrometry (TOF-SIMS). The investigated catalysts showed high stability and good recycling efficiency what makes them useful for a prolonged use. The factors influencing the selectivity of the supported catalysts were discussed.
In this work, the glycerol fermentation was carried out using Citrobacter freundii bacteria. The influence of glycerol and metabolites concentrations, and the pH changes on the efficiency of 1,3-propanediol production, during batch and fed-batch processes, was presented. The nanofiltration was used for the separation of obtained post-fermentation solutions. The resulted 1,3-PD solutions were significantly desalted, which may facilitate further downstream processes during 1,3-PD production.
The present study examines the impacts of dry mass content in pig liquid manure on its treatment with a filtration method. Samples of liquid manure with variable dry mass content were subjected to treatment using phosphoric acid, sulfuric acid, lime milk and superphosphate, as well as to thermal treatment, while in the last phase of pressure filtration. Increased dilution of the manure resulted in a reduced raw materials consumption ratio and improved filtration process efficiency, which ranged from 408 to 3765 kg/m2/h. The highest filtration efficiency was achieved using manure containing 3% dry mass, while the lowest efficiency was observed in manure at 10% dry mass. The increase in liquid manure dilution also reduced chemical oxygen demand in the filtrate, which ranged from 15 062 to 3656 mg/l. An appropriate manure dilution level, under the constant parameters of the treatment process, reduced phosphorus content in the filtrate to < 10 mg/kg while simultaneously enriching the post-filtration sediment with this precious fertilizing component.