Huili Liu

Optimization of the Preparation Conditions for Activated Carbons from Sugarcane Bagasse: An Agricultural Waste

The low-cost activated carbon was prepared from sugarcane bagasse, an agricultural waste material, by chemical activation with different reagents. Orthogonal experimental design was applied to study the influence of activation temperature, activation time and chemical ratio of reagents to sugarcane bagasse on the chemical activation process of sugarcane bagasse. The optimal activated carbon was obtained using impregnation ratio of 0.39-0.78% AlCl3 solution, 900-1000¡ãC activation temperature and 100min activation time, resulting in the carbon yield of 25.50-26.15% and the maximum adsorption of iodine of 600.57-604.46 mg/g. The activation time and temperature played an important role on the yield and the iodine number of the prepared activated carbon. The yield of the activated carbon decreased and the iodine number of the activated carbon increased with increasing carbonization time. Overall weight loss was found to increase with increasing temperature, resulting in decreasing yield of activated carbon as temperature increased. The iodine number of the prepared activated carbon increased with increasing activation temperature. In general, there were no significant changes in the shape of the XRD and FT-IR graphs and in the SEM photographs for the sugarcane bagasse precursor and the activated carbons prepared under optimum conditions.

Dissolution and Solubility Product of Cd-Fluorapatite [Cd5(PO4)3F] at pH of 2–9 and 25–45°C

Dissolution of the synthetic cadmium fluorapatite [Cd5(PO4)3F] at 25°C, 35°C, and 45°C was experimentally examined in HNO3 solution, pure water, and NaOH solution. The characterization results confirmed that the cadmium fluorapatite nanorods used in the experiments showed no obvious variation after dissolution. During the dissolution of Cd5(PO4)3F in HNO3 solution (pH = 2) at 25°C, the fluoride, phosphate, and cadmium ions were rapidly released from solid to solution, and their aqueous concentrations had reached the highest values after dissolution for ) was determined to be 10−60.03 (10−59.74∼10−60.46) at 25°C, 10−60.38 (10−60.32∼10−60.48) at 35°C, and 10−60.45 (10−60.33∼10−60.63) at 45°C. Based on the values obtained at an initial pH of 2 and 25°C, the Gibbs free energy of formation for Cd5(PO4)3F ( ) was calculated to be −4065.76 kJ/mol (−4064.11∼−4068.23 kJ/mol). The thermodynamic parameters for the dissolution process were computed to be 342515.78 J/K·mol, −85088.80 J/mol, −1434.91 J/K·mol, and 2339.50 J/K·mol for , , , and , correspondingly.

Speciation and Mobility of Heavy Metals in Tailings from Dachang Mine, China

Two carbonate tailing samples were collected from Dachang mine tailing reservoirs, Guangxi Province, China. The chemical speciation of Zn, As, Cd and Sb contained in tailing samples were determined by Dold seven-stage sequential extraction procedure, as well as mineralogical and chemical analysis. Then the potential migration abilities of these heavy metals were evaluated. The tailing analysis results showed that the main minerals were calcite, quartz, sphalerite and pyrite, the major elements were Si, S, Ca, Fe and Al, and the trace heavy metals included Zn, As, Cd and Sb. Zn mainly existed in secondary sulfide, primary sulfides and residual fraction, and As was in primary sulfide and residue, but Sb and Cd was residual fraction. The mobility of heavy metals followed the order: Zn > Sb > Cd > As.

A New Metal Ore Karst Deposition Form - Case Study for Dolomite Residual Deposit in Dongxiang Copper Mine, Jiangxi Province, China

The Kcd (Karst colluvium and deluvium) deposit of Dongxiang copper mine had long been considered as a kind of ancient diluvium, alluvium and proluvium in Cretaceous Karst depression. Based on lithology and morphology analysis of Kcd, and further research for regional hydrogeology and hydrogeochemistry, it was considered as a new special Karst deposition form of metal ore in this project. In the oxidation zone of sulfide mineral deposit, Kcd was a deposition mixture of dolomite powder (sand) and eluvium of dolomite wall rock, which were generated by the action of sulfuric acid water on wall rock, and the collapse deposition from the overlying K2n red beds. This kind of deposition was still generating and developing today. The monoclinal structure, primary sulfide mineral deposit occurred in clastic rock and claystone, dolomite and siliceous dolomite with 160m deep in underground water system, all that provided the development conditions of metal ore Karst deposition. This viewpoint could not only guide the copper ore exploration of Dongxiang type, but also provide a good case for Karst development in sulfide mineral areas.

Adsorption Removal of Phosphorus from Aqueous Solution by the Activated Carbon Prepared from Sugarcane Bagasse

The activated carbon was prepared firstly by soaking sugarcane bagasse in 0.39% AlCl3 solution, and then by carbonization in a charcoal kiln at 400oC for 2 days and activation in a muffle furnace at 900°C for 100 minutes. The adsorption removal of phosphorus from aqueous solution by the prepared activated carbons was studied in a batch adsorption system. The amount of phosphorus adsorbed per unit mass of adsorbent decreased from 1.13 to 0.33 mg/g and the removal percentage of phosphorus increased from 22.64 to 99.27% with increasing adsorbent dosages from 100 to 1500 mg in 50mL solution of the initial phosphorus concentration of 10mg/L. With increasing phosphorus concentrations from 1 to 30 mg/L, the amount of phosphorus adsorbed increased from 0.06 to 1.11 mg/g and the percent adsorption decreased from 91.93 to 57.34%. The dynamical data fit very well with the pseudo-second-order kinetic model (R2>0.9962) and the Langmuir model agreed well with the experimental data (R2>0.9648).

Synthesis and Characterization of the Ba5(PxAs1-xO4)3Cl Solid Solutions

A series of arsenate substituted chlorapatite was directly prepared through aqueous precipitation method. Characterization studies from elemental analysis, XRD, FT-IR spectra and SEM confirmed the forming of the arsenate/phosphate chlorapatite solid solutions. The XRD analysis indicated the typical solid solution phase of the apatite-type structure. In FT-IR spectra, the area of the phosphate peak was gradually suppressed and the arsenate peak increased as the proportion of the arsenate increased. The solids with As/(As+P) molar ratio of 0.49~1.0 were needle-like crystals; those with As/(As+P) molar ratio <0.19 were large tabular.

Adsorption and Coprecipitation of As(V) from Aqueous Solutions by Aluminum Hydroxide

The effects of solution pH and initial concentration on adsorption and coprecipitation of As(V) from aqueous solutions by aluminum hydroxide [Al(OH)3] for 50d and 1120d were studied. The XRD, FT-IR and SEM results indicated that there was only slight difference between the Al(OH)3 adsorbents before and after adsorption, but their crystal structure had not changed. The adsorption efficiency of As(V) onto Al(OH)3 increased with the increasing pH when pH<6.0. When pH>9, the adsorption efficiency decreased with the increasing pH. For the initial As(V) concentration Co=0.1 or 0.01 mmol/L, the adsorption efficiency exceeded 99% at pH 6-9 after 50d or 1120d reaction, but the As(V) concentration in the solution after adsorption for 1120d was higher than that for 50d.