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.

Analysis of Percolation of the Stabilized Suspensions of TiO2 and SiO2 Nanoparticles in Soil Columns Simulating Landfill Layers

It studied the behavior of transport and stability of TiO2 and SiO2 nanoparticles suspensions percolating through soil columns aiming at simulating municipal waste landfills covering soil layers performance. Experimental columns were constructed with landfill soils and water suspensions with nanoparticles percolation runs were carried out. The experimental columns were constructed with 100 mm and 200 mm of diameter and height, respectively. Outlet concentrations were measured along the percolation time using ICP-OES and nanoparticles tracking analyzer. It was observed that SiO2 nanoparticles acts as a stabilizer of TiO2 nanoparticles suspensions and promotes its transport through the soil columns, which simulates the conditions of the controlled landfills layers. The interaction of the suspensions of SiO2 nanoparticles with nanoparticles of TiO2, promote a high stability of the emulsions, which confers the high zeta potential present in SiO2 suspensions, promoting greater mobility and transport through the soil columns. The experimental results demonstrated that TiO2 nanoparticles were kept suspended, even after 10 days, which indicates good stability. It was observed that both TiO2 and SiO2 were kept in suspensions with negligible nanoparticles clustering and decantation. It was confirmed that the TiO2 and SiO2 of the outflow of soil columns are strongly affected by the soil pH, organic carbon and clay content of the soils. It was observed that the soil columns behave as a retention barrier for both TiO2 and SiO2 nanoparticles.

Model Experiment on Integral Seismic Behavior of Reinforced Concrete Frame with Split Columns

Based on a series of previous studies, an experiment on the integral seismic behavior of a 1/3 scaled model of two-bay and three-story reinforced concrete frame with split columns at lower two stories is performed under cyclic loading. The original columns at lower two stories of the model frame are short columns and they are replaced by the split columns. The hysteresis curves between the horizontal cyclic load and the lateral displacement at the top of the model frame, indicate that under the cyclic loading, the model frame undergoes the process of cracking, yielding, and maximum loading before being destroyed at the ultimate load. They also indicate that the model frame has better ductility, and the ratio of the ultimate displacement to the yielding displacement, reaches 6.0. The yielding process of the model frame shows that for the frame with split columns, plastic hinges are generated at the ends of beams and then the columns begin yielding while the frame still possesses the bearing and deformation capacity. The design idea of directly changing the short column to long one in the reinforced concrete frame may be realized by replacing the short column with the split one.

Effects of gravel on the water absorption characteristics and hydraulic parameters of stony soil

The eastern foothills of the Helan Mountains in China are a typical mountainous region of soil and gravel,where gravel could affect the water movement process in the soil.This study focused on the effects of different gravel contents on the water absorption characteristics and hydraulic parameters of stony soil.The stony soil samples were collected from the eastern foothills of the Helan Mountains in April 2023 and used as the experimental materials to conduct a one-dimensional horizontal soil column absorption experiment.Six experimental groups with gravel contents of 0%,10%,20%,30%,40%,and 50%were established to determine the saturated hydraulic conductivity(K_(s)),saturated water content(θ_(s)),initial water content(θ_(i)),and retention water content(θ_(r)),and explore the changes in the wetting front depth and cumulative absorption volume during the absorption experiment.The Philip model was used to fit the soil absorption process and determine the soil water absorption rate.Then the length of the characteristic wetting front depth,shape coefficient,empirical parameter,inverse intake suction and soil water suction were derived from the van Genuchten model.Finally,the hydraulic parameters mentioned above were used to fit the soil water characteristic curves,unsaturated hydraulic conductivity(K_(θ))and specific water capacity(C(h)).The results showed that the wetting front depth and cumulative absorption volume of each treatment gradually decreased with increasing gravel content.Compared with control check treatment with gravel content of 0%,soil water absorption rates in the treatments with gravel contents of 10%,20%,30%,40%,and 50%decreased by 11.47%,17.97%,25.24%,29.83%,and 42.45%,respectively.As the gravel content increased,inverse intake suction gradually increased,and shape coefficient,K_(s),θ_(s),andθ_(r)gradually decreased.For the same soil water content,soil water suction and K_(θ)gradually decreased with increasing gravel content.At the same soil water suction,C(h)decreased with increasing gravel content,and the water use efficiency worsened.Overall,the water holding capacity,hydraulic conductivity,and water use efficiency of stony soil in the eastern foothills of the Helan Mountains decreased with increasing gravel content.This study could provide data support for improving soil water use efficiency in the eastern foothills of the Helan Mountains and other similar rocky mountainous areas.

Leaching potential and changes in components of metals in two acidic ferrisols

Two acidic ferrisols, i.e., red soil （RS） and yellow red soil （YRS）, from the vicinity regions of non-ferrous ores in Hunan province of China, were leached with simulated acid rain through artificial column experiments. The results show that the total leaching mass of metals are m（Zn）〉m（Cu）〉m（Cd） from the original soils and m（Cd）〉m（Zn）〉〉 m（Cu） from the contaminated soils with external metals after leaching for 60 d continuously, leaching quantities of Cd and Zn from the contaminated red soil （CRS） are more than that from the contaminated yellow red soil （CYRS）, but for Cu, it is almost the same. The preferential fractions for leaching are mainly in exchangeable forms, and content of exchangeable forms decreases significantly in the contaminated soil profiles. The unstable fractions of Cd, Cu and Zn in the RS and YRS increase significantly with the decrease of pH value of simulated acid rain. Changes of fi, actions of external Cd, Cu, and Zn in the residual CRS and CYRS profiles are significantly affected by the acidity of acid rain, too. After leaching for 60 d continuously, Cd exists mostly in exchangeable form, Cu exists mainly in exchangeable, manganese oxide-occluded and organically bounding forms, and Zn exists in residual in CRS and CYRS profiles. Most of exchangeable Cd and Zn exist only small in surface layer （0-20 cm） and are transferred to the sub-layers, contrarily, Cu accumulates mostly in the topsoil （0-20 cm） with low translocation.

Effects of the Spatial Coupling of Water and Fertilizer on the Chlorophyll Fluorescence Parameters of Winter Wheat Leaves

Wheat is an important agricultural crop in the Loess region of China, where there is drought stress and low availability of soil nitrogen and phosphorus. Using a pulse modulation fluorometer, we studied the effects of water, nitrogen, and phosphorus on the kinetic parameters of chlorophyll fluorescence in winter wheat. The wheat was grown in layered columns of Eum-Orthic Anthrosol （Cinnamon soil）, with the water content and nutrient composition of each layer controlled. The results showed that the kinetic parameters of chlorophyll fluorescence were sensitive to water stress. The basic fluorescence （F0） of leaves was higher in the dry treatment （0-30 cm layer at 40-45% of field capacity, 30-90 cm at 75-80% of field capacity） compared to the wet treatment （entire soil column at 75-80% of field capacity）. The maximal fluorescence （Fm）, the variable fluorescence （Fv）, the photochemical efficiency （Fv/Fm） and potential activites （Fv/F0） of photosystem 2 （PS2） were significantly lower in the dry treatment. Although drought stress impaired PS2 function, this effect was significantly ameliorated by applying P or NP fertilizer, but not N alone. P application increased FJFm, both in well-watered and water stressed plants, especially when fertilizer was applied throughout the column or within the top 30 em of soil. A combined fertilizer improved photosynthesis in well watered plants, with Fm and F,fFm being the highest when fertilizer was applied throughout the columns. For drought stressed, plants FJFm was significantly greater when combined fertilizer was added within the top 30 cm of soil. We concluded that, when growing winter wheat in both arid and semi-arid parts of the Loess region of China, it is important to guarantee the nutrient supply in the top 30 cm of the soil.

Research on mechanism of groundwater pollution from mine water in abandoned mines

In order to understand the mechanism and regularity of the groundwater contamination from mine water of abandoned mines, experiments were conducted on an abandoned coal mine in Fuxin, a representative city with lots of mine water in northeast China. The groundwater pollution from different contaminants of coal-mining voids （total hardness, SO4^2-, CI^- and total Fe） and pollution factors transportation situation in the coal rock were simulated by soil column experiment under the conditions of mine water leaching and main water leaching （similar to rainwater leaching）, and the water-rock interaction mechanism was discussed during mine water infiltration through saturated coal rock by application of principle of mass conservation, based on physical properties of coal rock, as well as monitored chemical composition. The results show that, compared with the clear water leaching process, trends of change in pollutant concentrations presented different characteristics in the mine water leaching process. Groundwater is contaminated by the water rock interactions such as migration ＆ accumulation, adsorption ＆ transformation, dissolution ＆ desorption and ion exchange during the mine water permeation. The experiments also suggest that at first dissolution rate of some kinds of dissoluble salts is high, but it decreases with leaching time, even to zero during both the mine water leaching and main water leaching.

Colonization of Penicillium oxalicum enhanced neutralization effects of microbial decomposition of organic matter in bauxite residue

Bauxite residue is a highly alkaline waste product from refining bauxite ore.Bioremediation driven by microbial activities has been evidently effective in lowering the alkalinity of bauxite residues,which is critical to the initiation of pedogenesis under engineered conditions.The present study investigated the changes of alkalinity and aggregation of bauxite residue at different depth in response to the colonization of Penicillium oxalicum in columns.The results demonstrated that the inoculation of P.oxalicum decreased the residue’s pH to about 7 after 30 d only at the surface layer,which was exposed to aerobic conditions.The formation of aggregates was improved overall in the organic matter treated bauxite residue.However,the EC of bauxite residue increased with time under the incubation condition,probably due to accelerated hydrolysis of sodium-rich minerals.The inoculation of P.oxalicum had no effects on urease activity,but increased cellulose enzyme activity at surface layer only.

Settlement prediction model of slurry suspension based on sedimentation rate attenuation

This paper introduces a slurry suspension settlement prediction model for cohesive sediment in a still water environment. With no sediment input and a still water environment condition, control forces between settling particles are significantly different in the process of sedimentation rate attenuation, and the settlement process includes the free sedimentation stage, the log-linear attenuation stage, and the stable consolidation stage according to sedimentation rate attenuation. Settlement equations for sedimentation height and time were established based on sedimentation rate attenuation properties of different sedimentation stages. Finally, a slurry suspension settlement prediction model based on slurry parameters was set up with a foundation being that the model parameters were determined by the basic parameters of slurry. The results of the settlement prediction model show good agreement with those of the settlement column experiment and reflect the main characteristics of cohesive sediment. The model can be applied to the prediction of cohesive soil settlement in still water environments.

The transport and retention of CQDs-doped TiO_(2) in packed columns and 3D printed micromodels

CQDs-doped TiO_(2)(C-TiO_(2))has drawn increased attention in recent because of its excellent catalytic performance.Understanding the transport of C-TiO_(2)in porous media is necessary for evaluating the environmental process of this new nanomaterial.Column experiments were used in this study to investigate ionic strength(IS),dissolved organic matter(DOM)and sand grain size on the transport of C-TiO_(2).The mobility of C-TiO_(2)was inhibited by the increased IS and decreased sand grain size,but was promoted by the increased DOM concentration.The promotion efficiency of DOM ranked as humic acid(HA)>alginate(Alg)>bovine serum albumin(BSA),which was in the same order as their ability to change surface charges.The micromodels of pore network were prepared via 3D printing to further reveal the deposition mechanisms and spatial/temporal distribution of C-TiO_(2)in porous space.C-TiO_(2)mainly attached to the upstream region of collectors because of interception.The collector ripening was observed after long-time deposition.The existence of DOM caused visible decrease of C-TiO_(2)deposition in the pore network.HA caused the most remarkable reduce of deposition in the three types of DOM,which was consistent with the column experiment results.This research is helpful to predict the transport of C-TiO_(2)in natural porous media.

Precise separation and efficient recovery of Pd(Ⅱ)from high-level liquid waste by XAD-based adsorbents

Efficient separation of palladium(Pd(Ⅱ))from high-level liquid waste(HLLW)not only helps the safe disposal of nuclear waste,but also is a vital importan supplement to Pd(Ⅱ)resources.Herein,16 kinds of nove Amberlite XAD resins-based adsorbents were prepared by vacuum impregnation method for the separation of Pd(Ⅱ)from simulated HLLW,and the MMBT/XAD7HP prepared using 4-methyl-2-mercaptobenzothiazole(MMBT)as ligand and Amberlite XAD7HP resin(XAD7HP)as the carrier was selected as the optimal research object.Characterization analysis experiments proved the successful preparation of MMBT/XAD7HP,which exhibited ultrahigh adsorption selectivity for Pd(Ⅱ)(distribution coefficient(K_d)≥12584.5 ml·g^(-1),separation factor(SF_(Pd/M))≥2818.4)and superior adsorption capacity(Q≥130.1 mg·g^(-1)).The adsorption kinetics and adsorption isotherms for Pd(Ⅱ)matched with pseudo-secondorder(PSO)kinetics model and Langmuir model,indicating that the adsorption mode for Pd(Ⅱ)by MMBT/XAD7 HP was monolayer chemical adsorption.The dynamic column experiments showed that MMBT/XAD7 HP achieved efficiently separation of Pd(Ⅱ)from simulated HLLW,and the recovery rate was nearly 100% The adsorption mechanism was analyzed by Fourier transform infrared spectroscopy(FTIR),X-ray photoelectron spectroscopy(XPS)and density functional theory(DFT),and the ultrahigh selectivity of MMBT/XAD7 HP is attributed to the preferred affinity of the soft-N,S donor atoms in MMBT for Pd(Ⅱ).MMBT has the shortest frontline molecular orbital energy band gap(HOMO-LUMO)among the four ligands,which makes it easier to become an electron donor to attract Pd^(2+)to participate in coordination.NO_(3)^(-)participates in the adsorption to keep charge balance.In summary,MMBT/XAD7 HP has broad application prospects for the treatment of Pd(Ⅱ)in HLLW.

Selective extraction of lithium from shale gas produced water using an aluminum-based adsorbent

Two-dimensional layered aluminum-based adsorbents have been developed and successfully applied to enrich low-concentration lithium from shale gas produced water.The adsorbent,synthesized with a lithium-to-aluminum molar ratio of 0.6 in the salt solution,demonstrated exceptional performance characteristics.Its structure,featuring nano-encapsulated layers,facilitated lithium insertion,enhanced the surface area,and optimized pore size distribution for efficient adsorption.The adsorption equilibrium was reached within 60 min,closely aligning with the pseudo-second-order model.The isotherm analysis,based on the Sips model,suggested a nonhomogeneous multilayer adsorption process.Additionally,the adsorbent showed exceptional selectivity for Li^(+)over Na^(+),Ca^(2+),and Mg^(2+),ensuring effective lithium enrichment.Further desorption studies indicated that optimal conditions involved using deionized water at 333 K with a liquid-to-solid ratio of 80 mL/g.The adsorbent maintained robust performance and structural integrity through five adsorption-desorption cycles,highlighting its potential for recyclability and practical application in lithium recovery.These developments represent significant progress in harnessing lithium resources from shale gas produced water,thereby supporting advancements in clean energy technologies.

Transport of bacterial cell(E,coli)from different recharge water resources in porous media during simulated artificial groundwater recharge

Commonly used recharge water resources for artificial groundwater recharge(AGR)such as secondary effluent(SE),river water and rainfall,are all oligotrophic,with low ionic strengths and different cationic compositions.The dwelling process in recharge pond imposed physiologic stress on Escherichia coli(E.coli)cells,in all three types of investigated recharge water resources and the cultivation of E.coli under varying recharge water conditions,induced changes in cell properties.During adaptation to the recharge water environment,the zeta potential of cells became more negative,the hydrodynamic diameters,extracellular polymeric substances content and surface hydrophobicity decreased,while the cellular outer membrane protein profiles became more diverse.The mobility of cells altered in accordance with changes in these cell properties.The E.coli cells in rainfall recharge water displayed the highest mobility(least retention),followed by cells in river water and finally SE cells,which had the lowest mobility.Simulated column experiments and quantitative modeling confirmed that the cellular properties,driven by the physiologic state of cells in different recharge water matrices and the solution chemistry,exerted synergistic effects on cell transport behavior.The findings of this study contribute to an improved understanding of E.coli transport in actual AGR scenarios and prediction of spreading risk in different recharge water sources.

A Hierarchically Porous Metal-Organic Framework from Semirigid Ligand for Gas Adsorption

Hierarchically porous materials play an important role in facilitating mass transport and improving efficiency of adsorption and separation processes. In this paper, a new strategy is proposed to realize a hierarchically porous metal-organic framework （[Cu2（OH）（L）]＇（DMF）0.8 （FJU-11, H3L=3,5-（4-carboxybenzyloxy）benzoic acid, DMF= N,N-dimethylformamide） via using semi-rigid multi-carboxylic acids. Interestingly, FJU-11 possesses the large adsorption capacities and small isosteric heats toward CO2. The column breakthrough experiment for FJU-11 highlights its potential application in the separation of the flue gas.

Effectiveness of dicyandiamide as a nitrification inhibitor in biochar-amended soil

Overuse of nitrogen(N) fertilizers may lead to many environmental issues via N leaching into groundwater and agricultural runoff into surface water.Biochar, a sustainable soil amendment agent, has been widely studied because of its potential to retain moisture and nutrients. However, recent studies have shown that biochar has a very limited ability to improve the retention of negatively charged nitrite(NO2-) or nitrate(NO3-). Although positively charged ammonium(NH4+) can be better held by biochar, it is usually susceptible to nitrification and can be easily transformed into highly mobile NO2- and/or NO3-.In practice, dicyandiamide(DCD) has been used to inhibit nitrification, preserving N in its relatively immobile form as NH4+. Therefore, it is likely that the effects of DCD and biochar in soils would be synergistic. In this study, the influences of biochar on the effectiveness of DCD as a nitrification inhibitor in a biochar-amended soil were investigated by combining the experimental results of incubation, adsorption isotherm, and column transport with the simulated results of different mathematical models. Biochar was found to stimulate the degradation of DCD, as the maximum degradation rate slightly increased from 1.237 to 1.276 mg kg-1 d-1 but the half-saturation coefficient significantly increased from 5.766 to 9.834 mg kg-1. Considering the fact that the availability of DCD for nitrification inhibition was continuously decreasing because of its degradation, a novel model assuming non-competitive inhibition was developed to simulate nitrification in the presence of a decreasing amount of DCD. Depending on the environmental conditions, if the degradation of DCD and NH4+ in biochar-amended soil is not significant, improved contact due to the mitigated spatial separation between NH4+and DCD could possibly enhance the effectiveness of DCD.

Leaching of rare earth elements from contaminated soils using saponin and rhamnolipid bio-surfactant

The effective leaching of rare earth elements（La, Ce, Y and Eu） from simulated contaminated soil using bio-surfactant was investigated in a lab-scale column leaching experiment, where anionic biosurfactant rhamnolipid and non-ionic biosurfactant saponin were used as washing solutions. Soil properties and the rare earth element fractions were analysed to define the effect of leaching on soil and elemental speciation. Column leaching results showed that saponin solution was more effective than rhamnolipid in the removal of the four rare earth elements tested, with the accumulative removal efficiency of La, Ce, Y and Eu following flushing with 400 mL of 25 g/L saponin, reaching 35.258%, 26.072%, 31.476% and 30.849%, respectively. The change in REE speciation showed that REE removed from soils were mainly derived from the acid-soluble and residual fractions released when rhamnolipid solution was used as a leaching agent. However, for saponin leaching, removed REE amounts were derived from acid-soluble and reducible fractions. Complexation interactions were identified between saponin and REEs, according to infrared spectroscopy and ion exchange data, with saponin complexing with La, Ce, Y, and Eu at a complex ratio of 1：1.

Vadose-zone moisture dynamics under radiation boundary conditions during a drying process

In order to better understand the soil moisture dynamics during a drying process, a soil column experiment is conducted in the laboratory, followed by the numerical modeling with consideration of the coupled liquid water, water vapor and heat transport in the vadose zone. Results show that there are three distinct subzones above the water table according to the temporally dynamic variation of the water content profiles. Zone 1 sees a decrease in the water contents in the upper profiles （0 m-0.05 m） due to a negative net water flux in this zone where the upward isothermal water vapor flux becomes the main flow mechanism in the soils. Irl contrast, the water content within Zone 2 in the depth ranging from 0.05 m to 0.37 m sees an apparent increase over the, resulting from the positive net thermal water-vapor and isothermal liquid-water fluxes into this layer. Zone 3 （0.37 m-0.65 m） also sees an apparent decrease in the water content since the isothermal liquid water flux carries the liquid water either upward out of this region for vaporization or downward to the water table as a recharge to the groundwater.

Physical clogging experiment of sand gravel infiltration with Yellow River water in the Yufuhe River channel of Jinan, China

To make sense of physical clogging during Yellow River water spreading in the strong leakage zone of the Yufuhe River,a laboratory sand column experiment was undertaken and the heterogeneous sand gravel with a uniformity coefficient of 25.2 from the Yufuhe River was used as an infiltration medium.Under either the condition of raw sand or washed sand,physical clogging tests were conducted with constant hydraulic heads of 10 cm and 30 cm and inflow suspension concentrations of 200 mg/L,500 mg/L,and 1000 mg/L.The fine particles in the suspension and in the raw sand were considered exogenous and endogenous particles,respectively.Rapid clogging was observed in the porous medium when the inflow concentrations of the exogenous particles were high,and increased hydraulic head led to serious clogging.This result indicated that the Yufuhe River has a strong recharge capability with respect to clogging.The analysis of particle content shows that endogenous fine particles(diameter 1–10 mm and 50–74 mm)had less mobility and generally accumulated in the sand column,whereas particles with diameter 10–50 mm had greater mobility in the sand column.And the distribution of exogenous fine particles size after movement is relatively uniform in the sand column.Field observations indicated that the filtration effect of the aquifers have greatly improved the water quality of recharge water in the strong leakage zone of the Yufuhe River,and test data of turbidity also verified the results of the sand column experiments.