Papers by Keyword: Aqueous Solution

Abstract: Industrial waste containing heavy metals can pollute the aquatic environment. One method that can be done to manage heavy waste is the adsorption method that uses adsorbent from cassava stem powder. This research was conducted to utilize cassava stem powder waste for the adsorption of Pb2 + metal ions. Cassava stem powder was mashed until it passed 100 mesh sieve. Cassava stems have a cellulose content of 70-80%, lignin 15-20%, ADF 15-20% and cellulose can be used as an absorber of heavy metals. The adsorption process is carried out with variations in pH, time and concentration under optimum conditions. In this adsorption involves the functional groups contained therein so that the interaction between the adsorbent with the metal ion Pb2 +. Based on the research, the optimum conditions were obtained at pH 6, 180 minutes contact time and 50 ppm concentration. This test is carried out using Atomic Absorption Spectroscopy (AAS).

Abstract: The possibility of receiving of compositional Ni-P coating modified by potassium polytitanate was analyzed. An aqueous solution to obtain the composite coatings on the basis of nickel-phosphorus alloy modified by K₂О·nTiO₂ onto steel details of the friction knots was developed. The complex oxide K₂О·nTiO₂ represents a layered material from the scaly form nanocrystals with 20-80 nm thick and "diameter" 280 nm. The velocity forming of the modified compositional Ni-P coating was investigated, and the optimal quantity of the introduced potassium polytitanate (8 g/l), as a modified compound into solution, was determined, too. The tribological characteristics and micro-hardness of the resulting coatings depending on the chemical composition of solution and surface state of the rider were investigated.

Abstract: In this work, the preparation of cadmium telluride (CdTe) nanoparticles by aqueous solution method is presented. The preparation process was performed in the presence of an acidic agent (L-cys) at certain pH value. The x-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) of the prepared samples showed that poly crystalline structure with lowest particle size can be produced by controlling the period of heating process after the preparation step. Accordingly, this parameter can be used carefully to control the surface roughness of nanoscale CdTe samples to serve certain applications requiring some determined values of particle size and surface roughness.

Abstract: Pollution of heavy metals has become a serious environmental problem and it needs to be solved as soon as possible. Diatomite is a kind of biogenic rock and it is siliceous and sedimentary. There is abundant diatomite resource in China. Diatomite has distinctive structure of diatom monoblock. It has strong adsorbability, its specific area is large and it has high porosity. Its surface adheres a lot of active groups and negative charge. Diatomite with proper modification would show outstanding absorption effect of heavy metal ions. This paper reviewed the absorption efficiency of heavy metal ions on diatomite modified by metallic oxide, acids and bases, acticarbon, calcium carbonate and organics, the results would offer references for related researches. At last, this paper takes the outlook for the modified methods and application prospects of diatomite in wastewater treatment of heavy metals.

Abstract: Oxidation-stable copper (Cu) nanoparticles have been successfully prepared by electroless deposition in water at 353 K. Cupric oxide (CuO) and hydrazine (N₂H₄) are employed as the Cu precursor and reducing agent, respectively. The Cu nanoparticles have uniform particle sizes with average values ranging from 37 to 43 nm. The addition of gelatin has played a vital in role in controlling the particle size, agglomeration, and oxidation of Cu nanoparticles. In the absence of gelatin, both metallic Cu and cuprous oxide (Cu₂O) are present in the sample, indicating incomplete reduction of the CuO. Pure metallic Cu nanoparticles with excellent oxidation and dispersability in water can only be formed when gelatin is employed as protective agent. At higher amounts of gelatin, the particle size of the Cu nanoparticles is reduced.

Abstract: Eutrophication as a result of uncontrolled phosphorus (P) concentration that is released in wastewater has emerged as a major problem nowadays. Treatment of P demands high costs specifically to its chemical and maintenance needs. A lot of efforts were undertaken to find the most economical material that can treat P such as Electric Arc Furnace Slag (EAFS), a by-product from steel industry and Limestone (LS), and a natural resource that can be easily obtained from sedimentary rock. Despite numerous study conducted previously, the mechanism of P removal between these two materials have not been explored yet in detail. Therefore, an experimental work had been designed to evaluate the performance of P removal mechanism between the EAFS and LS lab-scale filter systems which can offer the best removal in overall. In this study a column lab scale of vertical rock filters in 100 mm diameter × 400 mm height were constructed for both EAFS and LS filters. The observation period was conducted for 2.5 months utilizing synthetic phosphorus concentration of 25 mg/L as its initial concentration. Working condition of the experiment was adjusted at pH 4.5 to 7.5 under 26.8±0.64 °C. X-ray fluorescence (XRF) analysis was also performed in order to determine chemical composition of EAFS and LS media. Results revealed that EAFS showed a significant effect on the removal of P mechanism compared to the LS filter system. The highest removal of P for both filter systems were observed to achieve 90% (pH 5) in the EAFS compared to only 68% (pH 4.5) in the LS system. This may be associated with the dissolution of Ca, Fe and Al elements in the EAFS that promotes precipitation process and hence gave higher removal compared to the LS element (only Ca has the highest percentage = 91%). At lower pH (acidic) condition the soluble metal salts react with phosphate ion to form phosphate hydrolysis product thus promoting precipitation in the system. In conclusion, it is predicted that precipitation may occur within the filter systems predominantly in the EAFS filter as pH was change from acidic to alkaline (4.5 – 7.5) due to dissolved (Al³⁺, Ca²⁺, Fe³⁺) within the filter system. Nevertheless, it is recommended that future study should be carried out on the precipitates salts through X-ray diffraction (XRD) analysis so as the existence of phosphate and metal salts as a result of precipitation can be finally confirmed.

Abstract: CdS-capped CdSe nanocrystals (NCs) which show high luminescence quantum yield are synthesized without any Poisonous Materials in aqueous solution. The synthesis in an aqueous medium without any poisonous materials is attached importance to. The absorption spectroscopy and photoluminescence spectroscopy are employed to analyze the NCs. It takes 78s that the intensity decreases to the half for bare CdSe NCs, but 442s for CdSe/CdS core/shell NCs. The photo stability of CdSe NCs under 325nm laser irradiation is enhanced greatly after CdS overcoating.

Abstract: The rapid development of biodiesel production yields large amount of glycerol as a by-product. It is a resource-utilization efficient and biological technical process to employ hydrogenolysis of glycerol aqueous solution for ethylene glycol generation. In this work, Raney Ni catalyst was prepared through conventional means and tested for hydrogenolysis of glycerol to produce ethylene glycol. The experiments were performed by varying the reaction time and rotate speed at a hydrogen pressure of 6.0-10.0MPa over a temperature range of 453-493K using a batch reactor. The effect of reaction conditions on the conversion of glycerol and the product distribution were also investigated and discussed. The results indicated that with the increase of reaction time the conversion of glycerol and the selectivity of 1,2-PDO tended to rise but the concentration of ethylene glycol decreased after reaching a peak point. The conversion of glycerol reached as much as 100% and the selectivity of ethylene glycol reached a maximum of 40%. Based on the experimental data, the reaction kinetics was studied and the parameters involved a two-site Langmuir-Hinshelwood model were acquired by the parameter estimation method. In the end, residual error distribution and statistic test showed that the obtained kinetic model was suitable and acceptable.

Abstract: The phase equilibira and surface tensions of N-methyldiethanolamine (MDEA), diethanolamine (DEA) and their aqueous solutions were investigated by using the perturbed-chain statistical associating fluid theory (PC-SAFT) and density-gradient theory (DGT). The molecular parameters and influence parameter were respectively regressed by fitting to the experimental data of phase equilibria and surface tensions of pure fluids. With the molecular parameters and influence parameter as input, the surface tensions of MDEA, DEA and their aqueous solutions were correlated satisfactorily.

Abstract: Carbon nanotubes (CNTs) were dispersed in aqueous solution with the inorganic compounds (H₃O₄₀PW₁₂ and H₃BO₃) by ultrasonic agitation. The dependency relationship between the inorganic solution concentration and CNTs dispersity was investigated by spectrophotometry. The results show that H₃O₄₀PW₁₂ and H₃BO₃ can promote CNTs dispersion in aqueous solution. CNTs disperse very well in the appropriate concentration. The optimal concentration of H₃O₄₀PW₁₂ solution is 2mg/mL, and the optimal concentration of H₃BO₃ solution is 4mg/mL. CNTs static stability in H₃BO₃ solution is better than that in H₃O₄₀PW₁₂. CNTs can still keep good dispersity in H₃O₄₀PW₁₂ solution under high speed centrifugation. The strong adsorption effect between CNTs surface and inorganic compound induces the dispersive stability of CNTs in aqueous solution.