Immobilization Rates Research Articles

Remediation of hexavalent chromium in water and soil by pristine and chemically modified pine barks: Effects and mechanisms

Chemical modification can greatly improve the adsorption performance of materials. In this study, pristine pine bark (PB) was modified by phosphoric acid (PA-PB), dodecyl trimethylammonium bromide (DTAB-PB) and cetyl trimethylammonium bromide (CTAB-PB) to test their influence on remediating hexavalent chromium [Cr(Ⅵ)] contamination in water and soil systems. Under the optimal experimental conditions in solution, the reduction/adsorption capacities and removal rates of Cr(Ⅵ) follow the order of CTAB-PB > PA-PB > DTAB-PB > PB, with CTAB-PB showing the highest capacity of 88.1 mg g−1. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Photoelectron Spectroscopy (XPS) indicated that adsorption coupled with reduction were the responsible mechanisms for Cr(Ⅵ) removal by pristine and modified PB, and modification with CTAB greatly improved Cr(Ⅵ) removal, especially the reduction of Cr(Ⅵ). When CTAB-PB and PB were applied in soil for a 30-day microcosm experiment, more than 93 % of Cr(Ⅵ) was converted into Cr(Ⅲ) at four different addition levels (2, 5, 10, and 15 wt%) with CTAB-PB exhibiting a faster immobilization rate than PB. In conclusion, CTAB-PB showed better performance than PB and is a promising material for the remediation of Cr(Ⅵ) contamination in water and soil.

Advances in the Study of NO3− Immobilization by Microbes in Agricultural Soils

The extensive application of nitrogen (N) fertilizers in agriculture has resulted in a considerable accumulation of N in the soil, particularly nitrate (NO3−), which can be easily lost to the surrounding environments through leaching and denitrification. Improving the immobilization of NO3− by soil microorganisms in agriculture is crucial to improve soil N retention capacity and reduce the risk of NO3− loss. In this paper, we reviewed the significance of microbial immobilization of soil NO3− in soil N retention, the techniques to quantify soil gross microbial NO3− immobilization rate, and its influencing factors. Specifically, we discussed the respective contribution of fungi and bacteria in soil NO3− retention, and we clarified that the incorporation of organic materials is of vital importance in enhancing soil microbial NO3− immobilization capacities in agricultural soils. However, there is still a lack of research on the utilization of NO3− by microorganisms of different functional groups in soil due to the limited techniques. In the future, attention should be paid to how to regulate the microbial NO3− immobilization to make soil NO3− supply capacity match better with the crop N demand, thereby improving N use efficiency and reducing NO3− losses.

Mechanisms of calcium-mediated As(V) immobilization by undissolved and dissolved biochar in saline-alkali environments

The environmental impact of arsenic (As) pollution has been a focal point within environmental science. In arsenic-polluted saline-alkali environment, the addition of exogenous biochar can affect the morphological transformation of As both through direct and indirect mechanisms, with calcium ions (Ca(II)) playing a crucial role. This study investigates the immobilization mechanisms of undissolved biochar (UOB) and dissolved biochar (DOB) on As(V) in the absence and presence of Ca(II) under alkaline conditions and aerobic atmosphere. While UOB and DOB alone are insufficient for As(V) immobilization, their combined action in the presence of Ca(II) achieves remarkable immobilization rates of 91.9% and 98.1%, respectively. Precipitation of calcium arsenate is identified as the primary immobilization pathway in both the UOB-Ca(II)-As(V) and DOB-Ca(II)-As(V) systems. Furthermore, Ca(II) acts as a mediator for As(V) immobilization through the formation of ternary UOB/DOB-Ca-As complexes, which are corroborated by Density Functional Theory (DFT) analysis from a microscopic perspective. Notably, the synergistic immobilization of As by DOB and newly generated CaCO3 in DOB-Ca(II)-As(V) system is highlighted. Additionally, the increase in Ca(II) concentration (0–100 mM) and solution pH (9.0–12.0) both significantly enhance the immobilization of As(V). An increase in the dosage of UOB (0.4–4 g/L) reduces the immobilization of As(V), while effect of the DOB concentration is insignificant. This study provides new insights into how the release of two biochar fractions into a typical Ca(II)-rich saline-alkali environment may alter the fate and transport of As species.

Integrated rather than organic farming history facilitates soil nitrogen turnover and N2O reduction in a green rye – silage maize cropping sequence

AbstractSoil gross mineral N production and consumption processes are crucial regulators of plant productivity and N loss from croplands. Substituting synthetic fertilizers by integrating legumes in cultivation systems is common in organic farming, but research on its long-term impact on dynamics of gross soil N transformation and associated environmental N loss is scarce. In particular, studies at a temporal resolution that allows for a mechanistic understanding of long-term effects of organic farming are missing. Therefore, we determined gross N turnover rates of ammonification, nitrification, and ammonium and nitrate immobilization at monthly temporal resolution during a full green rye-maize cropping sequence. Measurements were carried out at sites with same pedo-climatic background but organic farming (OF) and integrated farming (IF) history. During green rye growing, N turnover rates for OF and IF were low and not significantly different, likely owing to low temperatures. During silage maize growing, IF exhibited significantly higher average N turnover rates of 1.86, 4.46, and 5.57 mg N kg⁻1 dry soil d⁻1 for gross ammonification, ammonium immobilization, and nitrate immobilization, respectively, compared to OF values of 1.11, 1.80, and 2.90 mg N kg⁻1 dry soil d⁻1. The significantly higher N turnover rates were likely due to higher soil organic C, N and microbial biomass which result from different long-term management practices. Especially the increased immobilization potential on the IF site contributed to significantly lower area-scaled N₂O emissions (1.45 vs. 4.36 kg N ha⁻1) during periods of high nitrification. This shows that for low SOC soils, integrated farming history with high C return enhances soil N cycling and reduces the risk of N losses in the form of N2O emission.

Non-operative treatment of metacarpal fractures and patient-reported outcomes: a multicentre snapshot study

Abstract Purpose This study aimed to investigate practice variation in non-operative treatment methods and immobilisation duration for metacarpal fractures, and to evaluate patient-reported outcomes. Methods Conducted in 12 Dutch hospitals over three months in 2020, this study included adult patients with non-operatively treated solitary metacarpal fractures. Fractures were classified into intra-articular base, extra-articular base, shaft, neck, and intra-articular head fractures. The treatment methods (functional treatment allowing digit mobilisation or immobilisation) and immobilisation duration were assessed. Patient-reported outcomes were evaluated using the Michigan Hand Outcomes Questionnaire (MHQ) at three months post-trauma. Results Of 389 included patients, shaft fractures were most common (n = 150, 39%), with 93% immobilised, followed by fifth metacarpal neck fractures (n = 93, 24%), with 75% immobilised. Immobilisation rates for fifth metacarpal neck fractures varied between hospitals, ranging from 29% (95% CI 0.10–0.58) to 100% (95% CI 0.78–1.00). The median immobilisation duration for all fractures was 23 days (IQR: 20–28), and hospital setting was independently associated with this duration. Patients with metacarpal shaft fractures immobilised for less than 21 days had higher MHQ scores compared to those immobilised for 21 days or more (median (IQR) 83 (76–100) versus 71 (57–89), p = 0.026). Conclusions The results showed practice variation in the treatment of metacarpal fractures, especially in the treatment of fifth MC neck fractures, with some hospitals following the Dutch guideline that advocates functional treatment while others did not. There are suggestions that prolonged immobilisation of metacarpal shaft fractures may lead to a worse MHQ score. These findings underscore the need for adherence to treatment protocols and emphasize functional treatment to potentially improve patient outcomes and cost-effectiveness.

A global dataset of gross nitrogen transformation rates across terrestrial ecosystems

Rates of nitrogen transformations support quantitative descriptions and predictive understanding of the complex nitrogen cycle, but measuring these rates is expensive and not readily available to researchers. Here, we compiled a dataset of gross nitrogen transformation rates (GNTR) of mineralization, nitrification, ammonium immobilization, nitrate immobilization, and dissimilatory nitrate reduction to ammonium in terrestrial ecosystems. Data were extracted from 331 studies published from 1984–2022, covering 581 sites. Globally, 1552 observations were appended with standardized soil, vegetation, and climate data (49 variables in total) potentially contributing to the observed variations of GNTR. We used machine learning-based data imputation to fill in partially missing GNTR, which improved statistical relationships between theoretically correlated processes. The dataset is currently the most comprehensive overview of terrestrial ecosystem GNTR and serves as a global synthesis of the extent and variability of GNTR across a wide range of environmental conditions. Future research can utilize the dataset to identify measurement gaps with respect to climate, soil, and ecosystem types, delineate GNTR for certain ecoregions, and help validate process-based models.

For aqueous/soil cadmium immobilization under acid attack, does the hydroxyapatite converted from Pseudochrobactrum sp. DL-1 induced vaterite necessarily show higher stability?

Microbial induced carbonate precipitation (MICP) technology was widely applied to immobilize heavy metals, but its long-term stability is tough to maintain, particularly under acid attack. This study successfully converted Pseudochrobactrum sp. DL-1 induced vaterite (a rare crystalline phase of CaCO3) to hydroxyapatite (HAP) at 30 ℃. The predominant conversion mechanism was the dissolution of CdCO3-containing vaterite and the simultaneous recrystallization of Ca4.03Cd0.97(PO4)3(OH)-containing HAP. For aqueous Cd immobilization, stability test at pH 2.0–10.0 showed that the Cd2+ desorption rate of Cd-adsorbed vaterite (3.96–4.35 ‱) were 7.13–20.84 times greater than that of Cd-adsorbed HAP (0.19–0.61 ‱). For soil Cd immobilization under 60 days of acid-rain erosion, the highest immobilization rate (51.00 %) of exchangeable-Cd and the lowest dissolution rate (−0.18 %) of carbonate-Cd were achieved with 2 % vaterite, while the corresponding rates were 16.78 % and 1.31 % with 2 % HAP, respectively. Furthermore, vaterite outperformed HAP in terms of soil ecological thorough evaluation. In conclusion, for Cd immobilization by MICP under acid attack, DL-1 induced vaterite displayed direct application value due to its exceptional stability in soil and water, while the mineral conversion strategy we presented is useful for further enhancing the stability in water.

Enhancing soil gross nitrogen transformation through regulation of microbial nitrogen-cycling genes by biodegradable microplastics

Microplastics (MPs) in agricultural plastic film mulching system changes microbial functions and nutrient dynamics in soils. However, how biodegradable MPs impact the soil gross nitrogen (N) transformations and crop N uptake remain significantly unknown. In this study, we conducted a paired labeling 15N tracer experiment and microbial N-cycling gene analysis to investigate the dynamics and mechanisms of soil gross N transformation processes in soils amended with conventional (polyethylene, PE) and biodegradable (polybutylene adipate co-terephthalate, PBAT) MPs at concentrations of 0 %, 0.5 %, and 2 % (w/w). The biodegradable MPs-amended soils showed higher gross N mineralization rates (0.5–16 times) and plant N uptake rates (16–32 %) than soils without MPs (CK) and with conventional MPs. The MPs (both PE and PBAT) with high concentration (2 %) increased gross N mineralization rates compared to low concentration (0.5 %). Compare to CK, MPs decreased the soil gross nitrification rates, except for PBAT with 2 % concentration; while PE with 0.5 % concentration and PBAT with 2 % concentration increased but PBAT with 0.5 % concentration decreased the gross N immobilization rates significantly. The results indicated that there were both a concentration effect and a material effect of MPs on soil gross N transformations. Biodegradable MPs increased N-cycling gene abundance by 60–103 %; while there was no difference in the abundance of total N-cycling genes between soils without MPs and with conventional MPs. In summary, biodegradable MPs increased N cycling gene abundance by providing enriched nutrient substrates and enhancing microbial biomass, thereby promoting gross N transformation processes and maize N uptake in short-term. These findings provide insights into the potential consequences associated with the exposure of biodegradable MPs, particularly their impact on soil N cycling processes.

Macroporous hydrogel prepared via aqueous polymerization induced phase separation toward in situ immobilization of yeast

AbstractYeast‐loaded open‐cell macroporous poly(acrylamide) (PAM) hydrogels are prepared by polymerization induced phase separation (PIPS) with potassium persulfate (KPS)‐yeast as a redox initiator in a polyethylene glycol (PEG) aqueous solution. The presence of PEG not only allows the sizes of both void and interconnected pores of the hydrogels controllable, but also enlarges the void. Which makes it possible to embed cells in situ and efficiently transport nutrients inside the hydrogels. Yeasts are herein used to form a redox pair with KPS to run the polymerization of acrylamide (AM) at a mild temperature (less than 31°C), avoiding the cell inactivation during the polymerization. The in situ immobilization causes a uniformly distribution and high immobilization rate (~100%) of yeasts in the hydrogels. The hydrogels are then used to ferment glucose to produce ethanol, exhibiting high fermentation efficiency of 68%. After 10 cycles, the yeast can still maintain 86% of the initial fermentation efficiency. The yeasts maintain 87% and 93% of the initial cell activity after 1 week store at 4°C in dry state and in yeast extract peptone dextrose (YPD) medium, respectively. This study demonstrates that an aqueous PIPS initiated by peroxide‐target cells is an effective platform to efficiently in situ immobilize cells in a hydrogel for high performance fermentation.

Conversion mechanism of pyrolysis humic substances of cotton stalks and carbide slag and its excellent repair performance in Cd-contaminated soil

Unlike traditional biomass composting humification, pyrolysis humification can rapidly convert waste biomass into humic substances (HSs) at lower temperatures and in an alkaline environment for soil remediation. This study utilized the strong alkaline solid waste carbide slag (CARBIDE) and cotton stalk (CS) for pyrolysis humification. The pyrolysis humification mechanism and effect of CARBIDE and CS were investigated using FT-IR, NMR, and Py-GC/MS. Furthermore, the ability of HSs to remediate cadmium-contaminated soil (Cd-soil) was assessed through soil property analysis, pot tests, and microbial diversity studies. The results showed that humic acid (HA) and fulvic acid (FA) had the highest yield of 19 % and 5 %, respectively, among the humic substances (HS-CS&CA) produced under the conditions of 250 ℃, reaction time of 2 h and mass ratio of CS to CARBIDE of 5: 1. At 250 ℃, CARBIDE changed the heat transfer mechanism of biomass, promoted the decomposition of more hemicellulose and protein, promoted the Deamination, Ketonization and Maillard reaction, and synthesized more HAs. HS-CS&CA had a significant remediation effect on Cd-soil. The immobilization rate of Cd was as high as 23 %, and the accumulation of Cd in maize was reduced by 65 %. At the same time, the relative abundance of beneficial bacteria such as Xanthomonadaceae and Bacillaceae for immobilizing Cd was increased, and the cycling effect of N and P was also enhanced. This study provides an innovative technical route for the rapid humification of CARBIDE and CS and its application in Cd-soil remediation.

Immobilization and characterization of hormone-sensitive lipase (HSL) from Glaciozyma antarctica

HSL-like esterase (GlaEst12) was isolated from the psychrophilic yeast Glaciozyma antarctica, and has a broad substrate specificity hence allowing hydrolysis of a wide range of ester molecules. This characteristic makes it relevant in a variety of industries, including food processing, pharmaceutical, and bioenergy. Immobilization of HSL-like esterase from G. antarctica (GlaEst12) was achieved through physical adsorption onto different types of supports such as Amicogen LKZ118, Amicogen LKZ518, Accurel MP1000, Seplite LXC621, and Seplite LX120. Among these, LKZ518 and LX120 exhibited a high immobilization rate (95 - 100 %), surpassing the other tested supports. Nonetheless, their recorded enzyme activity was notably lower when contrasted with the activity observed on LKZ118. While LKZ118 displayed a 50 % immobilization rate, it demonstrated remarkably high enzyme activity compared to the other supports. The optimal enzyme concentration for immobilization was determined to be 5 mg per gram of LKZ118 support. The immobilized lipase (GlaEst12_LKZ118) showed an optimum temperature et 60 °C similar to free GlaEst12 when tested using pNP-octanoate substrate. However, it showed a shift in pH optimum from pH 8 for free GlaEst12 to pH 9 for GlaEst12_LKZ118. GlaEst12_LKZ118 demonstrated prolonged stability at 60 °C, with a half-life of 180 min. Furthermore, it exhibited stability in the presence of methanol when treated at 50 °C, and increased activity in the presence of DMSO. Operational stability tests revealed that GlaEst12_LKZ118 maintained 65.5 % of its relative activity after 7 cycles, indicating its robust operational stability. In summary, the study demonstrated the successful immobilization of HSL lipase derived from G. antarctica using various supports and the immobilized enzyme showed promising activity levels for potential applications in biodiesel production and flavour ester synthesis.

Differential impacts of polyethylene microplastic and additives on soil nitrogen cycling: A deeper dive into microbial interactions and transformation mechanisms

The impact of microplastics and their additives on soil nutrient cycling, particularly through microbial mechanisms, remains underexplored. This study investigated the effects of polyethylene microplastics, polyethylene resin, and plastic additives on soil nitrogen content, physicochemical properties, nitrogen cycling functional genes, microbial composition, and nitrogen transformation rates. Results showed that all amendments increased total nitrogen but decreased dissolved total nitrogen. Polyethylene microplastics and additives increased dissolved organic nitrogen, while polyethylene resin reduced it and exhibited higher microbial biomass. Amendments reduced or did not change inorganic nitrogen levels, with additives showing the lowest values. Polyethylene resin favored microbial nitrogen immobilization, while additives were more inhibitory. Amendment type and content significantly interacted with nitrogen cycling genes and microbial composition. Distinct functional microbial biomarkers and network structures were identified for different amendments. Polyethylene microplastics had higher gross ammonification, nitrification, and immobilization rates, followed by polyethylene resin and additives. Nitrogen transformation was driven by multiple functional genes, with Proteobacteria playing a significant role. Soil physicochemical properties affected nitrogen content through transformation rates, with C/N ratio having an indirect effect and water holding capacity directly impacting it. In summary, plastic additives, compared to polyethylene microplastics and resin, are less conducive to nitrogen degradation and microbial immobilization, exert significant effects on microbial community structure, inhibit transformation rates, and ultimately impact nitrogen cycling.

β-tricalcium phosphate enhanced biomineralization of Cd2+ and Pb2+ by Sporosarcina ureilytica HJ1 and Sporosarcina pasteurii HJ2

Microbiologically induced CaCO3 precipitation (MICP) has been proposed as a potential bioremediation method to immobilize contaminating metals. In this study, carbonate mineralizing bacteria HJ1 and HJ2, isolated from heavy metal contaminated soil, was employed for Cd2+ and Pb2+ immobilization with or without β-tricalcium phosphate addition. Compared with the only treatments amended with strains, the combined application of β-tricalcium phosphate and HJ1 improved the immobilization rates of Cd and Pb by 1.49 and 1.70 times at 24 h, and the combined application of β-tricalcium phosphate and HJ2 increased the immobilization rates of Cd and Pb by 1.25 and 1.79 times. The characterization of biomineralization products revealed that Cd2+ and Pb2+ primarily immobilized from the liquid phase as CdCO3 and PbCO3, and the addition of β-tricalcium phosphate facilitated the formation of Ca4.03Cd0.97(PO4)3(OH) and Pb3(PO4)2. Also, the calcium source was related to the speciation of carbonate precipitation and improved the Cd and Pb remediation efficiency. This research demonstrated the feasibility and effectiveness of MICP combined with β-tricalcium phosphate in immobilization of Cd and Pb, which will provide a fundamental basis for future applications of MICP to mitigate soil heavy metal pollutions.

Application of phosphogypsum and phosphate-solubilizing fungi to Pb remediation: From simulation to in vivo incubation

Phosphogypsum (PG) is the produced solid waste during phosphorus (P) extraction from phosphate rocks. PG is featured by its abundant PO43− and SO42−. This study investigated the utilization of PG as a material for lead (Pb) remediation, with the assistance of functional fungus. Aspergillus niger (A. niger) is a typical phosphate-solubilizing fungi (PSF), which has high ability to secret organic acids. Oxalic acid is its major secreted organic acid, which is often applied to enhance the P release from phosphate minerals. In this study, synthetic oxalic acid increased the immobilization rate of Pb2+ up to >99 % with the addition of PG. Then, it was observed that biogenic oxalic acid from A. niger can achieve comparable remediation effects. This was due to that PG could provide sufficient P for fungal growth, which allowed sustainable remediation. Subsequently, oxalic acid secreted by A. niger significantly increased the release of active P from PG, and then induced the formation of PPb minerals. In addition, other metabolites of A. niger (such as tyrosine-like substance) can also be complexed with Pb2+. Simultaneously, A. niger did not induce evidently elevation water-soluble fluorine (F) as PG contained abundant Ca2+. Moreover, this study elucidated that oversupply of PG promoted the formation of anglesite (Ksp = 1.6 × 10−8, relatively unstable), whereas the formation of lead oxalate (Ksp = 4.8 × 10−10, relatively stable) was reduced. This study hence shed a bright light on the sustainable utilization of PG for fungus-assisted remediation of heavy metals.

Aerated irrigation improves soil gross nitrogen transformations in greenhouse tomato: Insights from a 15N-tracing study

Aerated irrigation (AI) significantly influences soil nitrogen (N) dynamics and biochemical characteristics, which are crucial for enhancing N absorption and utilization efficiency. However, AI’s potential effects and mechanisms on gross soil N transformations remain unclear. In this study, a 15N tracing incubation experiment was conducted with four treatments, each receiving an equivalent N input (150 kg N ha–1): (1) AINPK, chemical fertilizer under AI; (2) AIOM, organic fertilizer (OM) under AI; (3) AINPK+OM, chemical fertilizer (75 % of applied N) with organic fertilizer (NPK+OM) under AI; (4) NPK, chemical fertilizer (NPK) under traditional drip irrigation. The results revealed that AINPK significantly increased crop yield by 12.42 %, gross N mineralization by 2.58-fold, and gross nitrification by 1.27-fold compared to NPK. The AIOM and AINPK+OM significantly increased yield by 18.74–12.34 %, gross N mineralization by 1.14–1.27-fold, and autotrophic nitrification by 1.05–1.11-fold compared to AINPK. The AIOM exhibits the highest rate of NH4+ immobilization, being 1.16–1.26-fold greater than the other three treatments. Moreover, AINPK significantly reduced the turnover time of organic N compared to NPK, and the turnover time of organic N of AIOM and AINPK+OM was shorter than AINPK. Overall, AI increased gross N mineralization and gross nitrification rates, enhancing soil N availability. AINPK and AIOM elevated the NH4+ immobilization rates compared to NPK, while the AIOM and AINPK+OM also enhanced NO3– immobilization rates, stimulating inorganic N retention capacity. Therefore, based on the N transformation dynamics observed in this study, AIOM and AINPK+OM, which accelerate organic N turnover, enhance N availability and retention capacity, and increase crop yields, are recommended for crop production in greenhouse tomato.

Comparison of the efficiency of traditional MICP and two-step MICP method for immobilizing heavy metals in aquatic environments

The application of the microbially induced carbonate precipitation (MICP) method for remediating heavy metals (i.e., HMs) has recently garnered significant attention. Nevertheless, the inhibition of urease activity by toxic Cd2+, Pb2+, Zn2+, and Cu2+ poses a challenge for MICP-based remediation of HMs contamination. This study: (1) first performed the traditional MICP tests (in which the bacterial solution, urea solution, and HMs were mixed simultaneously), and investigated the toxic effect of HMs on the urease activity and the immobilization efficiency, (2) analyzed the toxicity and immobilization mechanism during the MICP process by combining the simulation and XRD tests, (3) conducted the two-step MICP tests (which initially mixed the bacterial solution and urea solution to promote urea hydrolysis, then added the HMs solutions for HMs precipitation) to improve the immobilization efficiency. The tube experiments and simulations were investigated in the HMs concentration range from 1 to 10 mmol/L. Indicators including ammonium concentration, HMs concentrations, and pH were measured/recorded during the tests. The results show that soluble HMs exhibit a concentration-dependent inhibition of urea hydrolysis during the traditional MICP process, resulting in a decreasing immobilization efficiency. The two-step MICP method can effectively immobilize almost the Cd2+ and Zn2+ when the initial urea hydrolysis period exceeds 1–2 h. In addition, a high immobilization rate of over 90% can be achieved for Cu-contaminated solutions at the optimal first-step reaction time. Compared with the traditional MICP procedure, the effective two-step MICP method exhibits more promising application prospects for the immobilization of soluble HMs in aquatic environments.

Biochar as a highly efficient adsorption carrier for sewage sludge-derived nutrients and biostimulants: component fixation and mechanism

Production of liquid fertilizers containing nitrogenous nutrients and biostimulants from sewage sludge (SS-NB) has been attracting increasing attention due to its excellent fertilization effect and resource recycling attributes. To better understand the functional effects of nutrients and biostimulants in SS-NB on soil, the adsorption capacity and mechanism of straw biochar (SB) and wood chip biochar (WCB) for alkaline and neutral SS-NB components were investigated. The adsorption of total organic carbon (TOC) from alkaline and neutral SS-NB by WCB was 61.14% and 89.73%, respectively, higher than that by SB, which was 56.25% and 83.36%. Moreover, TOC from neutral SS-NB was more readily adsorbed, especially for fulvic and humic acids. SB had a strong adsorption capacity for calcium ions and nitrogen (TKN, nitrate N, protein, amino acid) and released large amounts of P. In addition, WCB and SB showed a strong affinity for macromolecules (proteins) and reducing substances (lignin and lipids) and excellent fixation ability for phytohormones and allelochemicals. However, WCB adsorbed more types of molecular substances than SB while maintaining a high immobilization rate. Analysis of the adsorption mechanism showed that surface amino groups of the biochar were involved in adsorption, while WCB had additionally high adsorption efficiencies through pore adsorption, hydrogen bonding adsorption and pore size-exclusion effects. The study revealed that biochar can be used as an efficient adsorption carrier for SS-NB to improve soil fertility management.Graphical

Immobilization Behavior and Mechanism of Cd2+ by Sulfate-Reducing Bacteria in Anoxic Environments

It is vital to remove cadmium from wastewater because of its potential harm to the natural environment and human health. It was found that sulfate-reducing bacteria (SRB) had a good fixing effect on Cd under a strict anaerobic environment. However, there are few reports on the immobilization effect and mechanism of SRB on Cd in an anoxic environment. This study revealed the effects of initial Cd2+ concentration, initial SO42− concentration, temperature, pH, and C/N ratio on the immobilization of Cd2+ by SRB in aqueous solution under an anoxic environment. The experimental results showed that under the conditions of initial concentration of Cd2+ within 0 mg/L~30 mg/L, initial concentration of SO42− within 1200 mg/L, temperature within 25 °C~35 °C, pH neutral, and C/N ratio of 20:1, the immobilization rate of Cd2+ by SRB is above 90%. The characterization results showed that bioadsorption and chemical precipitation were the main mechanisms of SRB immobilization of Cd2+ in an anoxic environment.

Synthesis of dioctyl sebacate catalysed by cellulose-immobilized lipase

Dioctyl sebacate is a long carbon chain dibasic acid ester with methylene as the main body. It is widely used in plasticizers because of its good cold resistance and high viscosity. And it has excellent properties of non-toxicity and easy biodegradation, so it can be used as a potential new green bio-based plasticizer. At present, most of the preparation methods of dioctyl sebacate are chemical methods, which have many by-products and cause environmental pollution. In this article, cellulose microspheres were used as a carrier to immobilize Candida antarctica lipase B (CALB) to catalyse the esterification of sebacic acid and n-octanol to prepare dioctyl sebacate. Through single factor experiments, the lipase immobilized on cellulose microspheres was optimized to determine the best process conditions: add 500 µL CALB to the erlenmeyer flask, and then add 0.02 mol/L PBS buffer (pH 8.0). After being prepared into a 5 mL system, 0.1 g of cellulose microspheres were added as a carrier and reacted for 3 h at 35 °C and 180 r/min. Added 0.5 vt% polyethylene glycol diglycidyl ether (PEGDEG) to the system for crosslinking. The final immobilization rate of lipase immobilized on cellulose microspheres was 80.06%, and the enzyme activity was 288.07 U/g. Using the cellulose-immobilized lipase as a catalyst, in the toluene system, the molar ratio of n (sebacic acid)/n (n-octanol) substrate was 1:3.5, the amount of immobilized enzyme was 0.04 g, 4 Å molecular sieve 1.5 g, 40 °C, and 150 r/min for 30 h, the conversion rate of dioctyl sebacate was 76.45%.

Medical waste incineration fly ash-based magnesium potassium phosphate cement: Calcium-reinforced chlorine solidification/stabilization mechanism and optimized carbon reduction process strategy

The traditional solidification/stabilization (S/S) technology, Ordinary Portland Cement (OPC), has been widely criticized due to its poor resistance to chloride and significant carbon emissions. Herein, a S/S strategy based on magnesium potassium phosphate cement (MKPC) was developed for the medical waste incineration fly ash (MFA) disposal, which harmonized the chlorine stabilization rate and potential carbon emissions. The in-situ XRD results indicated that the Cl− was efficiently immobilized in the MKPC system with coexisting Ca2+ by the formation of stable Ca5(PO4)3Cl through direct precipitation or intermediate transformation (the Cl− immobilization rate was up to 77.29%). Additionally, the MFA-based MKPC also demonstrated a compressive strength of up to 39.6 MPa, along with an immobilization rate exceeding 90% for heavy metals. Notably, despite the deterioration of the aforementioned S/S performances with increasing MFA incorporation, the potential carbon emissions associated with the entire S/S process were significantly reduced. According to the Life Cycle Assessment, the potential carbon emissions decreased to 8.35 × 102 kg CO2-eq when the MFA reached the blending equilibrium point (17.68 wt.%), while the Cl− immobilization rate still remained above 65%, achieving an acceptable equilibrium. This work proposes a low-carbon preparation strategy for MKPC that realizes chlorine stabilization, which is instructive for the design of S/S materials.