Batch and Column Experiments on Fluoride Removal from Waters Using Modified Zeolite

High fluoride groundwater occurs widely in China, presenting a quite serious environmental problem. Zeolite from Xinyang, China was tested as the fluoride removing adsorbent. Batch and column experiments on fluoride removal using modified zeolites treated with hydrochloric acid, sodium hydroxide, sodium chloride and ferric chloride, respectively show that 0.1 mol/L HCl modified zeolite can be used as an adsorbent for fluoride, with an adsorption capacity of 173.16 mg/kg.

Determination of the subcooled liquid solubilities of PAHs in partitioning batch experiments

Subcooled liquid solubility is the water solubility for a hypothetical state of liquid. It is an important parameter for multicomponent nonaqueous phase liquids （NAPLs） containing polycyclic aromatic hydrocarbons （PAHs）, which can exist as liquids even though most of the solutes are solid in their pure form at ambient temperature. So far, subcooled liquid solubilities were estimated from the solid water solubility and fugacity ratio of the solid and （subcooled） liquid phase, but rarely derived from experi- mental data. In our study, partitioning batch experiments were performed to determine the subcooled liquid solubility of PAHs in NAPL-water system. For selected PAH, a series of batch experiments were carried out at increased mole fractions of the target component in the NAPL and at a constant NAPL/ water volume ratio. The equilibrium aqueous PAH concentrations were measured with HPLC and/or GC- MS. The suhcooled liquid solubility was derived by extrapolation of the experimental equilibrium aqueous concentration to a mole fraction of unity. With the derived subcooled liquid solubility, the fugacity ratio and enthalpy of fusion of the solute were also estimated. Our results show a good agreement between the experimentally determined and published data.

Oxidation of Solid Phase and Ionic Strength Effect to the Cesium Adsorption on Pumice Tuff

In-situ oxidation of solid phase was considered to investigate adsorption behavior under different geochemical parameters like pH, initial concentration and ionic strength. Pumice tuff, a potential host rock for low and intermediate radioactive wastes, has been affected by the redox zone. The characterization of the fresh and oxidized tuff was performed by X-ray diffractometer, scanning electron microscope and mercury intrusion porosimetry. In order to compare the difference of distribution coefficient (Kd) in fresh and oxidized pumice tuffs, a batch adsorption study was carried out at the range of pH (4 - 12), ionic strength (0.003, 0.1, 1.0 and 3.0 mol/dm3) and initial cesium concentration (10dž, 10LJ, 10Lj and 10lj mol/dm3). Based on experimental Kd values, ionic strength was found to be the most influential factor, whereas the effects of pH, initial Cs concentration and weathering condition of pumice tuff were negligible. The recalculated Kd values suggest that the existing surface complexation model is applicable to explain the sorption coefficients through the wide range of solution conditions.

Mobility and speciation of Cd, Cu, and Zn in two acidic soils affected by simulated acid rain

Through a batch experiment, the mobility and speciation of heavy metals(Cd, Cu, Zn) in two acidic forest soils from Hunan Province were studied. The results showed that the release and potential active speciation of Cd, Cu, and Zn in the tested contaminated red soil(CRS) and yellow red soil(CYRS) increased significantly with pH decreasing and ion concentrations increasing of simulated acid rain, and these effects were mainly decided by the pH value of simulated acid rain. Cd had the highest potential risk on the environment compared with Cu and Zn. Cd existed mainly in exchangeable form in residual CRS and CYRS, Cu in organically bound and Mn-oxide occluded forms, and Zn in mineral forms due to the high background values.

Water quality and growth of phytoplankton for the Yellow River estuary reservoirs—The nutrients release from reservoir sediments

Effects of nutrients released from sediments on eutrophication in lakes and reservoirs were not well known in China. In the test, the release conditions of nitrogen and phosphorus from the sediments were observed by batch experiment. The test results revealed that the content released is correlated to the initial content of organic matter in sediments. In the Gengjing area, when the water quality of waterway, grit chamber and reservoir were compared, the water quality of the waterway was the highest, and lowered in the order of the grit chamber and the reservoir. The grit chamber could get not only fine sand removal but also the organic substance, nitrogen, phosphorus and phytoplankton, therefore it is important to operate and maintain the grit chamber to preserve the water quality of the reservoir. Due to little organic substance in sediments, ammonium nitrogen and phosphorus weren't released during the incubation. But from the absorptiometric turbidity unit (ATU) test results, although the release of ammonium concentration was very low, ammonium oxidizing and nitrite oxidizing bacteria existed in sediments.

Removal of arsenate and arsenite from aqueous solution by waste cast iron

The removal of As（III） and As（V） from aqueous solution was investigated using waste cast iron, which is a byproduct of the iron casting process in foundries. Two types of waste cast iron were used in the experiment： grind precipitate dust （GPD） and cast iron shot （CIS）. The X-ray diffraction analysis indicated the presence of Fe~ on GPD and CIS. Batch experiments were performed under different concentrations of As（III） and As（V） and at various initial pH levels. Results showed that waste cast iron was effective in the removal of arsenic. The adsorption isotherm study indicated that the Langmuir isotherm was better than the Freundlich isotherm at describing the experimental result. In the adsorption of both As（III） and As（V）, the adsorption capacity of GPD was greater than CIS, mainly due to the fact that GPD had higher surface area and weight percent of Fe than CIS. Results also indicated the removal of As（III） and As（V） by GPD and CIS was influenced by the initial solution pH, generally decreasing with increasing pH from 3.0 to 10.5. In addition, both GPD and CIS were more effective at the removal of As（III） than As（V） under given experimental conditions. This study demonstrates that waste cast iron has potential as a reactive material to treat wastewater and groundwater containing arsenic.

Effects of Organic Matter-Rich Amendments on Selenium Mobility in Soils

Soil organic matter (SOM) plays an important role in the Se dynamics in soil. The potential effects of vermicompost and digestate as important sources of SOM on selenium (Se) mobility were assessed in this study. Three soils differing in their physicochemical parameters, fluvisol, chernozem, and luvisol, were chosen, and three types of vermicomposts based on various bio-waste materials as digestate (vermicompost 1), kitchen waste with woodchips (vermicompost 2), and garden bio-waste (vermicompost 3) were used due to their high organic matter content. Additionally, digestate samples alone were applied. To evaluate the potential effect of vermicompost application on sorption characteristics of soils, batch sorption experiments were performed. The results showed a predominant effect on Se species in the soils, where selenite sorbed more intensively compared to selenate, regardless of the soil and ameliorative material applied. In the control, the soil sorption ability of selenite tended to decrease in the order: fluvisol > luvisol > chernozem. However, these differences were not significant. Moreover, the effects of the ameliorative materials depended on both soil and amendment used. In fluvisol, all the amendment applications resulted in a decrease in distribution coefficient ( K d values) of Se, whereas in chernozem, this effect was observed only for the digestate-based vermicompost 1. Increasing K d levels were reported in luvisol treated with digestate;the application of garden bio-waste-based vermicompost 3 tended to decrease the K d values. Further studies are required on long-term effects of these amendments on Se mobility in soils and the role of individual organic matter fractions in this context.

Acid resistance of methanogenic bacteria in a two-stage anaerobic process treating high concentration methanol wastewater

In this study,the two-stage upflow anaerobic sludge blanket(UASB)system and batch experiments were employed to evaluate the performance of anaerobic digestion for the treatment of high concentration methanol wastewater.The acid resistance of granular sludge and methanogenic bacteria and their metabolizing activity were investigated.The results show that the pH of the first UASB changed from 4.9 to 5.8 and 5.5 to 6.2 for the second reactor.Apparently,these were not the advisable pH levels that common metha-nogenic bacteria could accept.The methanogenic bacteria of the system,viz.Methanosarcina barkeri,had some acid resis-tance and could still degrade methanol at pH 5.0.If the meth-anogenic bacteria were trained further,their acid resistance would be improved somewhat.Granular sludge of the system could protect the methanogenic bacteria within its body against the impact of the acidic environment and make them degrade methanol at pH 4.5.The performance of granular sludge was attributed to its structure,bacteria species,and the distribution of bacterium inside the granule.

Amending a tropical Arenosol:increasing shares of biochar and clay improve the nutrient sorption capacity

Tropical Arenosols may be challenging for agricultural use,particularly in semi-arid regions.The aim of this study was to evaluate the impact of the addition of increasing shares of biochar and clay on the nutrient sorption capacity of a tropical Arenosol.In batch equilibrium experiments,the sorption of ammonium-N(NH_(4)^(+)-N),nitrate-N(NO_(3)^(−)-N),potassium(K^(+)),and phosphate-P(PO_(4)^(3−)-P)was quantified for mixtures of an Arenosol with increasing shares of biochar and clay(1%,2.5%,5%,10%,100%)and the unmixed Arenosol,biochar,and clay.The mid-temperature biochar was produced from Prosopis juliflora feedstock;the clayey material was taken from the sedimentary parent material of a temporarily dry lake.Only the Arenosol-biochar mixture with 10%biochar addition and the biochar increased the NH_(4)^(+)-N maximum sorption capacity(q_(max))of the Arenosol,by 34%and 130%,respectively.The q_(max)of PO_(4)^(3−)-P slightly increased with ascending biochar shares(1-10%)by 14%,30%,26%,and 42%,whereas the undiluted biochar released PO_(4)^(3−)-P.Biochar addition slightly reduced NO_(3)^(−)-N release from the Arenosol but strongly induced K^(+)release.On the other hand,clay addition of 10%and clay itself augmented q_(max)of NH_(4)^(+)-N by 30%and 162%;ascending clay rates(1-100%)increased q_(max)for PO_(4)^(3−)-P by 78%,130%,180%,268%,and 712%.Clay rates above 5%improved K^(+)sorption;however,no q_(max)values could be derived.Sorption of NO_(3)^(−)-N remained unaffected by clay amendment.Overall,clay addition proved to enhance the nutrient sorption capacity of the Arenosol more effectively than biochar;nonetheless,both materials may be promising amendments to meliorate sandy soils for agricultural use in the semi-arid tropics.