Chai Liyuan

Preliminary bioleaching of heavy metals from contaminated soil employing indigenous Penicillium Chrysogenum strain F1

Bioleaching is an environment-friendly and economical technique to remove heavy metals from contaminated soil. The objective of this work is to find out an indigenous strain to remedy soil contaminated by Zn, Pb, Cu and Cd. A strain which was selected from the soil of a local smelting industry was found to be able to produce many organic acids and degrade pH value of the liquid medium. The fungus strain is identified as Penicillium Chrysogenum (P. Chrysogenum) by sequencing 18srDNA and ITS. Bioleaching condition using P. Chrysogenum is optimized. Glucose is the best carbon source for P. Chrysogenum and inorganic nitrogen is better than organic nitrogen. In addition, neutral solution and room temperature are fit for P. Chrysogenum to bioleach. In the one-step bioleaching, the bioleaching ratios are 39.95% for Zn, 9.4% for Pb, 34.89% for Cu and 49.59% for Cd, which are 53.89% for Zn, 14.44% for Pb, 55.53% for Cu and 62.81% for Cd in the two-step bioleaching. The efficiency of two-step bioleaching is better than the one-step bioleaching. P. Chrysogenum is effective in removing heavy metals from the contaminated soil.

Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO2 composite electrodeposition

Electrochemical behaviors of Zn-Fe alloy and Zn-Fe-TiO2 composite electrodeposition in alkaline zincate solutions were studied respectively by the methods of linear potential sweep and cyclic voltammetry. From the results it can be concluded that Zn shows under potential deposition, Zn-Fe alloy codeposition is anomalous codeposition and Zn-Fe alloy cathode polarization is increased with the introduction of additive. From the view point of electrochemistry, the reasons that the content of Fe in the Zn-Fe coating changes with the composition of the electrolyte and the process conditions altering and the relationship between the content of Fe and the appearance of the coating are interpreted. The cathode polarization of Zn-Fe alloy codeposition is enhanced obviously with addition of additive. In the course of composite electrodeposition, TiO2 has less promotion to electrodeposition of zinc ions than to iron ions, while the electrodeposition of iron ions improves the content of TiO2 in composite coating, which is in agreement with the results of process experiments.

Removal of lead in wastewater by immobilized inactivated cells of Rhizopus oligosporus

A novel technology for lead removal with nonliving Rhizopus oligosporus immobilized in calcium alginate was studied. The results show that the main influencing factors include pH value and interfering cations. pH value has different effects on biosorption of various heavy metals and lead adsorption can be proceeded by controlling pH value in a range of 2–5; interfering cations especially Cu(II) can make the adsorption amount of Pb(II) decrease by immobilized Rhizopus oligosporus. Desorption efficiency of different eluants and kinetics were investigated. Citrate acid with concentration of 0.3 mol · L−1 is the best for the elution of Pb(II) and desorption rate is over 98% when the reaction equilibrium reaches 3 h. Immobilized biomass keeps high lead biosorption capacity after five cycles of regeneration.

Comparison for Adsorption Modeling of Heavy Metals (Cd, Pb, Cu, Zn) from Aqueous Solution by Bio-Formulation

The demand for effective and inexpensive sorbents is increasing in response to the widespread recognition of the deleterious health effects of heavy metals exposure through aqueous solutions. An adsorbent, bio-formulation (BF), was prepared by agricultural waste. The maximal biosorption removal of cadmium (II), lead(II), copper(II), zinc(II) on BF are 99.4, 99.8, 97.6, 98.3% at pH 8, 5, 5, 7, respectively. Freundlich adsorption isotherm is well fitted to the experimental data. The adsorption kinetics of heavy metals reveal that adsorption of heavy metals is very rapid within the first 30 min and equilibrium time is independent of initial concentration. The adsorption process follows second-order sorption kinetics. The biosorption mechanism may be cation exchange effect.

Preparation of adhesive for bamboo plywood using concentrated papermaking black liquor directly

Adhesive for bamboo plywood prepared directly using lignin existing in the black liquor as a kind of material replacing phenol was proposed on the basis of the same structural properties of lignin and phenol. The results indicate that the reaction time of black liquor methylating is 30 min, when the ratio of alkali to formaldehyde is controlled at approximately 0.20, decomposition rate of formaldehyde is the lowest and the effect of black liquor methylating is the best, the optimal molar ratio of phenol: formaldehyde to NaOH to H2O of preparing phenolic resin is 1.00 : 1.50 : 0.50 : 9.00, and the suitable viscosity is 27–30 Pa · s. At different mass ratios of methylated black liquor to phenolic resin, all terms of performance of black liquor phenolic resin are excellent and satisfy the requirement. All terms of performance of bamboo plywood prepared using this technique are better than that of excellent bamboo plywood of national criteria. Using this technique, the cost is depressed by 28.69% without altering the traditional adhesive producing technique flow, and without using additional equipment.

Electrochemical behaviors of gold and its associated elements in various complex agent solutions

Thermodynamic properties and electrochemical behaviors of gold and its associated elements, such as silver, copper, nickel and iron, in various complex agent solutions were studied. Within CS(NH2)2, S2O32− and SCN− systems, alkaline thiourea is the optimal nontoxic lixiviating agent substituting cyanide from the viewpoint of thermodynamics. The electrochemical study indicates that the anodic dissolution current densities of gold are 2.616, 1.805, 1.267, 1.088, 0.556, and 0.145 mA · cm−2 respectively in the solutions of cyanide, alkaline thiourea containing Na2SiO3, SCN−, acidic thiourea, alkaline thiourea and thiosulfate at the potential of 0.500 V. Comparing various lixiviating agents, the alkaline thiourea solution containing Na2SiO3 is of prominent selectivity in leaching gold, in the potential range from 0.500 to 0.600 V, which is most efficient for leaching gold selectively instead of cyanide. The effect on leaching gold is similar to that in the cyanide system.

Optimization of efficient stable reagent of alkaline thiourea solution for gold leaching

Na2SiO3 and Na2SeO3 were chosen as stable reagents of alkaline thiourea solution substituting Na2SO3, according to the structure-property relationship between the stability of alkaline thiourea and the structure of thiourea and sulfite ion, and the effect of the stable reagents on stability of alkaline thiourea was investigated. The results show that contrary to Na2SeO3, Na2SO3 and Na2SiO3 affect the stability of alkaline thiourea solution remarkably. The stable effect of Na2SiO3 on alkaline thiourea is obviously better than that of Na2SO3. The stable reagents Na2SO3 and Na2SiO3 decrease the decomposition rate of alkaline thiourea solution greatly, and the decomposition rate of alkaline thiourea reduces from 72.5% to 33.8% with addition of 0.3 mol · L−1 Na2SiO3. Dissolution currents of gold in the alkaline thiourea solution containing Na2SO3 and Na2SiO3 are 2.0 mA · cm−2 and 3.5 mA · cm−2 at the potential of 0.42 V, respectively, and Na2SO3 is consumed excessively due to the oxidation reaction of Na2SO3 occurring in the studied potential range. Na2SiO3 is an efficient stable reagent of alkaline thiourea solution, and gold dissolution is accelerated much more obviously by Na2SiO3 than by Na2SO3.

Study on the Thermal Treatment of Nano-Ag/TiO2 Thin Film

The photocatalytic degradation rates of methyl orange and antibacterial properties of nano-Ag/TiO2 thin film on ceramics were investigated in this study. XRD was used to detect the structure of film to clarify the impacts on the rates and properties. The effect of film layers, heating temperature, heating time, and embedding of Ag

Effect and influence factors of sulfur removal in coal with fungus

The influence of coal desulfurization by fungus was experimentally studied. The results suggest that fungus can effectively remove inorganic and organic sulfur in coal, and main influences of desulfurization by fungus of pH value, temperature, coal slurry concentration and coal granularity were studied by orthodox experiment and the optimal experimental conditions are as follows: pH value 6, temperature 45 °C, coal slurry concentration 10% and coal granularity 100 µm. Under above conditions, fungus can remove up to 44.96% total sulfur and 54.87% inorganic sulfur within two days, and their desulfurization rates will increase along with time. Compared with sulfolobas, desulphurization by fungus is steady and more effective, and has advantage of high speed.

Biosorption Kinetics and Thermodynamics of Arsenate and Arsenite on Spent Grains

The biosorption of arsenate and arsenite from aqueous solutions by spent grains, a by-product of the brewing process, was investigated. The effects of solution pH, contact time and temperature were studied in batch experiments. The initial removal is rapid and equilibrium was established in less than 180 min. Good correlation coefficients were obtained for the pseudo second-order kinetic model. The enthalpy of sorption was exothermic and the increase in As(III) removal was larger than that of As(V) over the same rise in temperature. Spent grains are a potential biosorbent for the removal of As(V) and As(III) from the effluent of metallurgical industry.