Dissolution and solubility of the calcium-nickel carbonate solid solutions [(CaNi)CO] at 25 °C.

A series of the calcium-nickel carbonate solid solutions [(CaNi)CO] were synthesized and their dissolution in N-degassed water (NDW) and CO-saturated water (CSW) at 25 °C was experimentally investigated. During dissolution of the synthetic solids (Ni-bearing calcite, amorphous Ca-bearing NiCO and their mixtures), the Ni-calcite and the Ca-NiCO dissolved first followed by the formation of the Ni-bearing aragonite-structure phases. After 240-300 days of dissolution in NDW, the water solutions achieved the stable Ca and Ni concentrations of 0.

Performance and Mechanism of Co and Mn Loaded on Fe-Metal-Organic Framework Catalysts with Different Morphologies for Simultaneous Degradation of Acetone and NO by Photothermal Coupling.

VOCs can be used instead of ammonia as a reducing agent to remove NO, achieving the effect of removing VOCs and NO simultaneously. Due to the high energy consumption and low photocatalytic efficiency required for conventional thermocatalytic purification, photothermal coupled catalytic purification can integrate the advantages of photocatalysis and thermocatalysis in order to achieve the effect of pollutants being treated efficiently with a low energy consumption. In this study, samples loaded with Co and Mn catalysts were prepared using the hydrothermal method on Fe-MOF with various morphologies.

Optimization of Photothermal Catalytic Reaction of Ethyl Acetate and NO Catalyzed by Biochar-Supported MnO-TiO Catalysts.

The substitution of ethyl acetate for ammonia in NH-SCR provides a novel strategy for the simultaneous removal of VOCs and NO. In this study, three distinct types of biochar were fabricated through pyrolysis at 700 °C. MnO and TiO were sequentially loaded onto these biochar substrates via a hydrothermal process, yielding a family of biochar-based catalysts with optimized dosages.

Biotransformation of Chlorpyrifos MR-1 in the Presence of Goethite: Experimental Optimization and Degradation Products.

In this study, the degradation system of MR-1 and goethite was constructed with chlorpyrifos as the target contaminant. The effects of initial pH, contaminant concentration, and temperature on the removal rate of chlorpyrifos during the degradation process were investigated. The experimental conditions were optimized by response surface methodology with a Box-Behnken design (BBD).

Goethite Enhances Cr(VI) Reduction by MR-1 under Different Conditions: Mechanistic Insights.

Chromium (Cr) contamination, widely present in the environment, poses a significant threat to both ecology and human health. Microbial remediation technology has become a hot topic in the field of heavy metal remediation due to its advantages, such as environmental protection, low cost, and high efficiency. This paper focused on using various characterization and analysis methods to investigate the bioreduction effect and mechanism of microorganisms on Cr(VI) under various influencing factors.

Study on the performance and mechanism of cobaltous ion removal from water by a high-efficiency strontium-doped hydroxyapatite adsorbent.

In this study, a high-efficiency strontium-doped hydroxyapatite (Sr-HAP) adsorbent was synthesized by a sol-gel method for removing cobaltous ions (Co(II)) from water. The effects of adsorbent dose, initial solution pH, initial Co(II) concentration and temperature on the removal performance of Co(II) were investigated. Experimental results indicated that the optimum Sr-HAP dose was 0.

Synchronous in-situ sludge reduction and enhanced denitrification through improving electron transfer during endogenous metabolisms with Fe(Ⅱ) addition.

The creation of large amounts of excess sludge and residual nitrogen are critical issues in wastewater biotreatment. This study introduced Fe(II) into an oligotrophic anaerobic reactor (OAR) that was implemented to modify an anoxic-oxic process to motivate in-situ sludge reduction and enhance denitrification under an effective electron shuttle among organic matter, nitrogen, and Fe. The addition of 15 mg L Fe(II) resulted in a sludge reduction efficiency reached 32.

Intensified denitrification in a fluidized-bed reactor with suspended sulfur autotrophic microbial fillers.

Sulfur-based autotrophic denitrification (SAD) is a promising low-carbon approach to tackle nitrate pollution. However, practical SAD reactor implementation faces challenges of slow denitrification rates and prolonged start-up periods. In this work, a fluidized-bed denitrification reactor with suspended composite fillers immobilized with elemental sulfur and SAD bacteria was constructed.

Trade-off of abiotic stress response in floating macrophytes as affected by nanoplastic enrichment.

Nanoparticles have been found in large-scale environmental media in recent years, causing toxic effects in various organisms and even humans through food chain transmission. The ecotoxicological impact of microplastics on specific organisms is currently receiving much attention. However, relatively little research to date has examined the mechanisms through which nanoplastic residue may exert an interference effect on floating macrophytes in constructed wetlands.

Effects of Pretreatment and Polarization Shielding on EK-PRB of Fe/Mn/C-LDH for Remediation of Arsenic Contaminated Soils.

In this study, coupling electrokinetic (EK) with the permeable reactive barriers (PRB) of Fe/Mn/C-LDH composite was applied for the remediation of arsenic-contaminated soils. By using self-made Fe/Mn/C-LDH materials as PRB filler, the effects of pretreatment and polarization shielding on EK-PRB of Fe/Mn/C-LDH for remediation of arsenic contaminated soils were investigated. For the pretreatment, phosphoric acid, phosphoric acid and water washing, and phosphate were adopted to reduce the influence of iron in soil.

[Preparation of Magnetic Iron Oxide/Mulberry Stem Biochar and Its Effects on Dissolved Organic Carbon and Arsenic Speciation in Arsenic-Contaminated Soils].

In this study, original mulberry-biochar (M-BC) and magnetic iron oxide/mulberry stem biochar (Fe-BC) materials were prepared and characterized using mulberry stems as the raw material. The effects of carbonized temperature of Fe-BC and M-BC on dissolved organic carbon (DOC) and arsenic(As) speciation in soil leaching solutions were studied using soil incubation experiments. The results showed that:① Fe-BC was mainly composed of FeO and was magnetic, and the main functional groups were a C＝O double bond, O-H bond, C-O bond, and Fe-O bond.

Strontium-doped hydroxyapatite as adsorbent effectively to remove lead ions from water.

In this study, a strontium-doped hydroxyapatite (Sr-HAP) was synthesized by the solgel method, which was used as adsorbent to remove lead ions (Pb) from water. The results showed that the adsorption capacities of the Sr-HAP were obviously higher than those of the HAP, the adsorption capacities of which for Pb reached 651.175 mg/g.

Nitrogen Removal From Nitrate-Containing Wastewaters in Hydrogen-Based Membrane Biofilm Reactors Hydrogen Autotrophic Denitrification: Biofilm Structure, Microbial Community and Optimization Strategies.

The hydrogen-based membrane biofilm reactor (MBfR) has been widely applied in nitrate removal from wastewater, while the erratic fluctuation of treatment efficiency is in consequence of unstable operation parameters. In this study, hydrogen pressure, pH, and biofilm thickness were optimized as the key controlling parameters to operate MBfR. The results of 653.

Effective Remediation of Arsenic-Contaminated Soils by EK-PRB of Fe/Mn/C-LDH: Performance, Characteristics, and Mechanism.

Arsenic is highly toxic and carcinogenic. The aim of the present work is to develop a good remediation technique for arsenic-contaminated soils. Here, a novel remediation technique by coupling electrokinetics (EK) with the permeable reactive barriers (PRB) of Fe/Mn/C-LDH composite was applied for the remediation of arsenic-contaminated soils.

Dissolution and solubility of calcite-rhodochrosite solid solutions [(CaMn)CO] at 25 °C.

A complete series of calcite-rhodochrosite solid solutions [(CaMn)CO] are prepared, and their dissolution processes in various water samples are experimentally investigated. The crystal morphologies of the solid solutions vary from blocky spherical crystal aggregates to smaller spheres with an increasing incorporation of Mn in the solids. Regarding dissolution in N-degassed water, air-saturated water and CO-saturated water at 25 °C, the aqueous Ca and Mn concentrations reach their highest values after 1240-2400 h, 6-12 h and < 1 h, respectively, and then decrease gradually to a steady state; additionally, the ion activity products (log_IAP) at the final steady state (≈ solubility products in log_K) are estimated to be - 8.

[Remediation Performance via the Passivation of a Porous Biomorph Genetic Composite of -FeO/FeO/C Using a Bamboo Template on As(Ⅴ) Contaminated Soils].

Red soil from Guangxi, China was selected as the background soil, and a porous biomorphic genetic composite of -FeO/FeO/C comprising a bamboo template (PBGC-Fe/C) was used as a passivator to remediate As(Ⅴ) contaminated soils. The performance of PBGC-Fe/C was characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The results showed that PBGC-Fe/C could improve the passivation effect of As(Ⅴ) from the contaminated soils compared with a single passivation material.

Mn-Fe Layered Double Hydroxide Intercalated with Ethylene-Diaminetetraacetate Anion: Synthesis and Removal of As(III) from Aqueous Solution around pH 2-11.

A novel adsorbent Mn-Fe layered double hydroxides intercalated with ethylenediaminete-traacetic (EDTA@MF-LDHs) was synthesized by a low saturation coprecipitation method. The behavior and mechanism of As(III) removed by EDTA@MF-LDHs were investigated in detail in comparison with the carbonate intercalated Mn-Fe layered double hydroxides (CO@MF-LDHs). The results showed that EDTA@MF-LDHs had a higher removal efficiency for As(III) than As(V) with a broader pH range than CO@MF-LDH.

A comparative study on the dissolution and stability of beudantite and hidalgoite at pH 2-12 and 25-45 °C for the possible long-term simultaneous immobilization of arsenic and lead.

Beudantite and hidalgoite were synthesized and characterized to investigate their possible immobilization for arsenic and lead in acidic and oxidizing environments by a long-term dissolution. The synthetic beudantite [Pb(HO)Fe(AsO)(SO)(OH)] was spherulitic pseudo-cubic crystals with nearly smooth surface. The synthetic hidalgoite [Pb(HO)Al(AsO)(SO)(OH)] was well-formed pseudo-cubic, pseudo-cuboctahedral or pseudo-octahedral crystals.

[Passivation and Remediation Effects and Mechanisms of Plant Residual Modified Materials on Lead-Contaminated Soils].

The specific characteristics and mechanism of passivation of Pb in soil were studied using HAP/C composite (PBGC-HAP/C) as passivation, and using proportion of PBGC-HAP/C, particle size and type of passivator, soil moisture content, soil pH value of Pb, and particle size of the material as influencing factors. The results showed that with an increase in dosage of the passivator and passivation time, the passivation effect increases gradually. Reducing the particle size of the passivator is beneficial to improving the passivation effect.

Purification Behavior of Zn(II) in Water by Magnesium Hydroxyapatite: Surface Complexation, and Dissolution-Precipitation.

As an innovative and economical material, hydroxyapatite does little harm to the environment. In this study, a magnesium hydroxyapatite (Mg-HAP) adsorbent was prepared by doping magnesium. Magnesium doping can increase the hydroxyl groups on the surface of Mg-HAP to form more adsorption sites and improve the removal effect of the heavy metal Zn(II) in water.

[Removal of Pb from Aqueous Solution by Magnesium-Calcium Hydroxyapatite Adsorbent].

A novel magnesium-calcium hydroxyapatite adsorbent was prepared by the Sol-gel method with different proportions of Mg/(Ca+Mg) using Mg as doped ions, and the removal characteristics and process mechanism of Pb on the magnesium-calcium hydroxyapatite in an aqueous solutions were studied. The results show that the surface of the adsorbent is composed mainly of a hydroxyphosphonite compound[Pb(PO)(OH)], The morphological characteristics of the magnesium-calcium hydroxyapatite adsorbent surface was investigated as crystal structure changes from short rods to needle structures according to scanning electron microscopy (SEM). Testing at a temperature of 25℃ and pH of 5 showed that the adsorption of Pb by magnesium-calcium hydroxyapatite reached equilibrium within 720 min.

Arsenic immobilization from aqueous solution by the precipitation of the pseudo-octahedral arsenate-substituted natroalunite solid solutions.

A series of the arsenate-substituted natroalunite solid solutions were synthesized by hydrothermal precipitation at 200 °C and pH of 4 and characterized to investigate the AsO substitution for SO in natroalunite as the base of a possible immobilization method for arsenic. The AsO substitution in natroalunite increased when the [AsO/(AsO + SO)] molar ratios of the initial aqueous solutions increased and the maximum substitution reached ~67% molar for the [AsO/(AsO + SO)] = 0.26.

Spectral insight into thiosulfate-induced mercury speciation transformation in a historically polluted soil.

We studied the effect of different doses (0.5%, 2% and 5% (w/w)) of ammonium thiosulfate on mercury (Hg) speciation fractionation following its addition to the soil, as well as its accumulation by oilseed rape (Brassica napus L.), corn (Zea mays L.