scholarly journals High Efficiency Stabilization of Lead in Contaminated Soil by Thermal-organic Acid Activated Phosphate Rock

2021 ◽  
Author(s):  
Ziwen Song ◽  
Zhuo Zhang ◽  
Canyu Luo ◽  
Likun Yang ◽  
Jin Wu
Keyword(s):  
Oxalic Acid ◽  
Organic Acid ◽  
Contaminated Soil ◽  
Phosphate Rock ◽  
High Efficiency ◽  
Fold Increase ◽  
Low Grade ◽  
Rock Powder ◽  
Composition And Structure ◽  
Stabilization Effect

Abstract Phosphate rock powder (PR) has been shown to possess the potential to stabilize lead (Pb) in soil. Most of the phosphorus (P) minerals in the world are low-grade ores, which makes it difficult to achieve the expected stabilization effect on heavy metals. This study compared the changes in the phase composition and structure of PR and three kinds of activated phosphate rock powder (APR) (organic acid activated PR, thermal activated PR, and thermal-acid activated PR), and used APR for the stabilization of Pb-contaminated soil. PR/APR was characterized by different methods. The stabilization effectiveness of APR on Pb-contaminated soil was evaluated by toxicity leaching procedure, the Pb products adsorbed on APR and stabilization mechanism of APR on Pb were analyzed. The results showed that the crystallinity of fluorapatite phase decreased after all the activation treatments. The APR showed decreased crystallinity and 3.4-fold increase in specific surface area, and a 53.07% and 49.32% increase in soluble P content in oxalic acid activated PR and citric acid activated PR, respectively, when compared with those of PR. These changes improved the stabilization effect of APR on Pb-contaminated soil, and the stabilization effectiveness was as follows: thermal-acid activated PR > organic acid activated PR > thermal activated PR. In particular, oxalic acid-600℃ activated PR showed the best effect, presenting 94.0%-99.8% reduction in Pb leaching concentration following addition of 2%-10% modifier. Product characterization after Pb adsorption on APR showed that Pb was adsorbed onto APR by forming pyromorphite precipitation with APR.

scholarly journals Research progress in activation of phosphorus containing substances and remediation of heavy metal pollution in soil

2020 ◽  
Vol 165 ◽  
pp. 02033
Author(s):  
Wang Na
Keyword(s):  
Heavy Metal ◽  
Metal Pollution ◽  
Heavy Metal Pollution ◽  
Phosphate Rock ◽  
Phosphorus Deficiency ◽  
Rapid Development ◽  
Utilization Efficiency ◽  
Research Progress ◽  
Low Grade ◽  
Rock Powder

The phenomenon of soil phosphorus deficiency in China is very serious, which limits the agricultural production in China. Low molecular weight organic acids and phosphorus solubilizing microorganisms are widely distributed in the soil, and can be used as activators to improve the content of phosphorus in the soil. With the rapid development of industry and agriculture in China, heavy metal pollution in the environment is becoming more and more serious. China is rich in phosphate rock resources, but the grade of phosphate rock is low and the utilization efficiency is not high. Using phosphate rock to deal with heavy metal pollution has been favored by environmental scholars. This paper analyzes the main composition and application of phosphate rock in China, the activation of phosphate rock powder, the remediation effect and mechanism of phosphate rock powder and activated phosphate rock powder on heavy metals in soil, providing theoretical basis for the scientific utilization of low-grade phosphate rock and the treatment of heavy metal pollution.

Overview of Current Phosphoric Acid Production Processes and a New Idea of Kiln Method

2020 ◽  
Vol 17 ◽  
Author(s):  
Guangya Zheng ◽  
Jupei Xia ◽  
Zhengjie Chen
Keyword(s):  
Phosphoric Acid ◽  
Acid Production ◽  
Phosphate Rock ◽  
Low Grade ◽  
Production Methods ◽  
Production Processes ◽  
Major Equipment ◽  
Development Prospects ◽  
Great Competitiveness

: China primarily contains medium and low-grade phosphorus ores that are used to produce phosphoric acid. Here, we provide an overview of phosphoric acid production processes, including wet, thermal, and kiln methods, as well as the fundamental principles, major equipment, and technological aspects of each process. Progress in the kiln method using lowgrade phosphate rock is described, which involves the KPA and CDK processes. The literature shows that the addition of admixtures adds great competitiveness to kiln phosphate production methods and has considerable development prospects.

scholarly journals Feasibility of fly ash as fluxing agent in mid- and low-grade phosphate rock carbothermal reduction and its reaction kinetics

2021 ◽  
Vol 10 (1) ◽  
pp. 157-168
Author(s):  
Biwei Luo ◽  
Pengfei Li ◽  
Yan Li ◽  
Jun Ji ◽  
Dongsheng He ◽  
...  
Keyword(s):  
Particle Size ◽  
Fly Ash ◽  
Reaction Time ◽  
Carbothermal Reduction ◽  
Industrial Waste ◽  
Phosphate Rock ◽  
Molar Ratio ◽  
Low Grade ◽  
Carbon Excess ◽  
Fluxing Agent

Abstract The feasibility of industrial waste fly ash as an alternative fluxing agent for silica in carbothermal reduction of medium-low-grade phosphate ore was studied in this paper. With a series of single-factor experiments, the reduction rate of phosphate rock under different reaction temperature, reaction time, particle size, carbon excess coefficient, and silicon–calcium molar ratio was investigated with silica and fly ash as fluxing agents. Higher reduction rates were obtained with fly ash fluxing instead of silica. The optimal conditions were derived as: reaction temperature 1,300°C, reaction time 75 min, particle size 48–75 µm, carbon excess coefficient 1.2, and silicon–calcium molar ratio 1.2. The optimized process condition was verified with other two different phosphate rocks and it was proved universally. The apparent kinetics analyses demonstrated that the activation energy of fly ash fluxing is reduced by 31.57 kJ/mol as compared with that of silica. The mechanism of better fluxing effect by fly ash may be ascribed to the fact that the products formed within fly ash increase the amount of liquid phase in the reaction system and promote reduction reaction. Preliminary feasibility about the recycling of industrial waste fly ash in thermal phosphoric acid industry was elucidated in the paper.

scholarly journals Characterization of Aerosol Composition, Aerosol Acidity and Organic Acid Partitioning at an Agriculture-Intensive Rural Southeastern U.S. Site

2018 ◽  
Author(s):  
Theodora Nah ◽  
Hongyu Guo ◽  
Amy P. Sullivan ◽  
Yunle Chen ◽  
David J. Tanner ◽  
...  
Keyword(s):  
Oxalic Acid ◽  
Organic Acids ◽  
Organic Acid ◽  
Organic Aerosol ◽  
Water Soluble ◽  
Molar Concentration ◽  
Particle Phase ◽  
Aerosol Composition ◽  
Phase Water ◽  
Acetic Acids

Abstract. The implementation of stringent emission regulations has resulted in the decline of anthropogenic pollutants including sulfur dioxide (SO2), nitrogen oxides (NOx) and carbon monoxide (CO). In contrast, ammonia (NH3) emissions are largely unregulated, with emissions projected to increase in the future. We present real-time aerosol and gas measurements from a field study conducted in an agricultural-intensive region in the southeastern U.S. during the fall of 2016 to investigate how NH3 affects particle acidity and SOA formation via the gas-particle partitioning of semi-volatile organic acids. Particle water and pH were determined using the ISORROPIA-II thermodynamic model and validated by comparing predicted inorganic HNO3-NO3− and NH3-NH4+ gas-particle partitioning ratios with measured values. Our results showed that despite the high NH3 concentrations (study average 8.1 ± 5.2 ppb), PM1 were highly acidic with pH values ranging from 0.9 to 3.8, and a study-averaged pH of 2.2 ± 0.6. PM1 pH varied by approximately 1.4 units diurnally. Formic and acetic acids were the most abundant gas-phase organic acids, and oxalate was the most abundant particle-phase water-soluble organic acid anion. Measured particle-phase water-soluble organic acids were on average 6 % of the total non-refractory PM1 organic aerosol mass. The measured molar fraction of oxalic acid in the particle phase (i.e., particle-phase oxalic acid molar concentration divided by the total oxalic acid molar concentration) ranged between 47 and 90 % for PM1 pH 1.2 to 3.4. The measured oxalic acid gas-particle partitioning ratios were in good agreement with their corresponding thermodynamic predictions, calculated based on oxalic acid’s physicochemical properties, ambient temperature, particle water and pH. In contrast, gas-particle partitioning of formic and acetic acids were not well predicted for reasons currently unknown. For this study, higher NH3 concentrations relative to what has been measured in the region in previous studies had minor effects on PM1 organic acids and their influence on the overall organic aerosol and PM1 mass concentrations.

scholarly journals Peningkatan Produksi Gula Pereduksi dari Tandan Kosong Kelapa Sawit dengan Praperlakuan Asam Organik pada Reaktor Bertekanan

REAKTOR ◽  
2017 ◽  
Vol 16 (4) ◽  
pp. 199
Author(s):  
Fahriya Puspita Sari ◽  
Nissa Nurfajrin Solihat ◽  
Sita Heris Anita ◽  
Fitria Fitria ◽  
Euis Hermiati
Keyword(s):  
Enzymatic Hydrolysis ◽  
Oxalic Acid ◽  
Organic Acid ◽  
Oil Palm ◽  
Maleic Acid ◽  
Reducing Sugar ◽  
Sugar Production ◽  
Empty Fruit Bunch ◽  
Acid Pretreatment ◽  
Severity Factor

ENHANCEMENT OF REDUCING SUGAR PRODUCTION FROM OIL PALM EMPTY FRUIT BUNCH BY PRETREATMENT USING ORGANIC ACID IN PRESSURIZED REACTOR. Organic acids are potential to create more environmentally friendly process in the pretreatment of lignocellulosic biomass for bioethanol production. This study was aimed to investigate the influence of organic acid pretreatment in reducing sugar production in a pressurized reactor with various resident times and temperatures on enzymatic hydrolysis of OPEFB. Two different organic acids (maleic acid and oxalic acid) were used in the pretreatment of oil palm empty fruit bunch (OPEFB) using a pressurized reactor. Factorial design using three different temperatures (170, 180, and 190°C) and four resident times (15, 30, 45, and 60 min) were employed, followed by enzymatic hydrolysis. Each condition conducted two repetitions. Analysis was conducted on the reducing sugar that was produced after saccharification by means of the severity factor of each pretreatment condition. Maleic acid showed higher reducing sugar yield with lower severity factor than oxalic acid with the same operating conditions. The highest yield of reducing sugars (80.84%) was obtained using maleic acid at 170 for 60 minutes with severity factor of 1.836. Keywords: bioethanol; organic acid pretreatment; pressurized reactor; severity factor; oil palm empty fruit bunches;   Abstrak Asam organik berpotensi dalam membantu proses praperlakuan dari biomassa lignoselulosa untuk memproduksi bioetanol yang ramah lingkungan. Penelitian ini bertujuan untuk mengetahui pengaruh asam organik, suhu dan waktu operasi terhadap produksi gula pereduksi dengan reaktor bertekanan pada tandan kosong kelapa sawit. Dua asam organik yang berbeda yaitu asam oksalat dan asam maleat digunakan untuk proses praperlakuan tandan kosong kelapa sawit (TKKS) dengan bantuan reaktor bertekanan. Dalam proses praperlakuan digunakan tiga suhu yang berbeda yaitu suhu 170, 180, dan 190°C dan empat waktu operasi 15, 30, 45, dan 60 min yang dilanjutkan dengan proses hidrolisis enzimatis. Setiap kondisi dilakukan dua kali pengulangan. Analisa yang digunakan adalah analisa uji gula pereduksi dan severity factor pada kondisi tiap praperlakuan. Asam maleat menunjukkan hasil yang lebih baik dengan severity factor yang lebih rendah dibandingkan menggunakan asam oksalat dengan kondisi operasi yang sama. Hasil yang didapatkan menunjukkan bahwa praperlakuan tandan kosong kelapa sawit dengan bantuan reaktor bertekanan memiliki rendemen gula pereduksi optimum sebesar 80,84% dengan menggunakan asam maleat pada suhu 170°C selama 60 menit dengan severity factor sebesar 1,836. Kata kunci: bioetanol; praperlakuan asam organik; reaktor bertekanan; severity factor; tandan kosong kelapa sawit.

scholarly journals Inhibitor potency varies widely among tumor-relevant human isocitrate dehydrogenase 1 mutants

2018 ◽  
Vol 475 (20) ◽  
pp. 3221-3238 ◽  
Author(s):  
Diego Avellaneda Matteo ◽  
Grace A. Wells ◽  
Lucas A. Luna ◽  
Adam J. Grunseth ◽  
Olga Zagnitko ◽  
...  
Keyword(s):  
Isocitrate Dehydrogenase ◽  
Resistance Mutation ◽  
Poor Response ◽  
Fold Increase ◽  
Structural Features ◽  
Low Grade ◽  
Wild Type ◽  
Isocitrate Dehydrogenase 1 ◽  
Dynamics Simulations ◽  
Mutant Idh1

Mutations in isocitrate dehydrogenase 1 (IDH1) drive most low-grade gliomas and secondary glioblastomas and many chondrosarcomas and acute myeloid leukemia cases. Most tumor-relevant IDH1 mutations are deficient in the normal oxidization of isocitrate to α-ketoglutarate (αKG), but gain the neomorphic activity of reducing αKG to D-2-hydroxyglutarate (D2HG), which drives tumorigenesis. We found previously that IDH1 mutants exhibit one of two reactivities: deficient αKG and moderate D2HG production (including commonly observed R132H and R132C) or moderate αKG and high D2HG production (R132Q). Here, we identify a third type of reactivity, deficient αKG and high D2HG production (R132L). We show that R132Q IDH1 has unique structural features and distinct reactivities towards mutant IDH1 inhibitors. Biochemical and cell-based assays demonstrate that while most tumor-relevant mutations were effectively inhibited by mutant IDH1 inhibitors, R132Q IDH1 had up to a 16 300-fold increase in IC50 versus R132H IDH1. Only compounds that inhibited wild-type (WT) IDH1 were effective against R132Q. This suggests that patients with a R132Q mutation may have a poor response to mutant IDH1 therapies. Molecular dynamics simulations revealed that near the NADP+/NADPH-binding site in R132Q IDH1, a pair of α-helices switches between conformations that are more wild-type-like or more mutant-like, highlighting mechanisms for preserved WT activity. Dihedral angle changes in the dimer interface and buried surface area charges highlight possible mechanisms for loss of inhibitor affinity against R132Q. This work provides a platform for predicting a patient's therapeutic response and identifies a potential resistance mutation that may arise upon treatment with mutant IDH inhibitors.

scholarly journals Effect of Soil Washing Using Oxalic Acid on Arsenic Speciation and Bioaccessibility in Soils

2020 ◽  
Vol 42 (4) ◽  
pp. 218-227
Author(s):  
Yeseul Gwon ◽  
Seong Ryeol Kim ◽  
Eun Jung Kim
Keyword(s):  
Particle Size ◽  
Oxalic Acid ◽  
Contaminated Soil ◽  
Arsenic Speciation ◽  
Arsenic Concentration ◽  
Size Fraction ◽  
Soil Washing ◽  
Large Particle Size ◽  
Amorphous Oxides ◽  
Particle Size Fractions

Objectives : Soil washing process has been widely applied for remediation of contaminated soil with arsenic and heavy metals in Korea. The application of soil washing could change physical and chemical properties of soils and metal speciation in soil, which could affect the risk to the environment and human health. Thus, it is necessary to evaluate metal and arsenic speciation and their mobility in soil after soil remediation in order to evaluate effectiveness of soil remediation process and manage soil quality effectively. The purpose of this study is to evaluate the risk of arsenic in soil after remediation of arsenic contaminated soil via soil washing.Methods : Arsenic contaminated soil collected at the abandoned mine site was washing with oxalic acid. The arsenic contaminated soil was divided into 2,000-500 µm, 500-250 µm, 250-150 µm, 150-75 µm, 75-38 µm, < 38 µm particle size fractions. After soil washing for each soil particle size fraction, arsenic speciation via sequential extraction and bioaccessibility in the soils were evaluated. Results and Discussion : Generally, arsenic and metal concentrations were higher in the soil fractions with smaller particle sizes. But high arsenic concentration was observed at the large particle size fractions (>250 µm), which might be due to the presence of mineral phases containing arsenic such as arsenolite or pyrite in the large particle size fraction soils. Sequential extraction showed that arsenic in mine soils was majorly present as associated with amorphous oxides. After soil washing with oxalic acid, arsenic in soils associated with amorphous oxides was greatly decreased, whereas the arsenic fraction associated sulfide and organic matter was increased. Soil washing decreased the bioaccessible arsenic concentration (mg/kg) in soil, but increased the bioaccessibility (%) depending on the soil characteristics. Conclusions : Soil washing changed arsenic species in soils, which affected mobility and risk of arsenic in soil.

RESEARCH OF COMPLEX MODIFICATION OF HEAVY CONCRETE

2021 ◽  
Vol 96 (4) ◽  
pp. 107-112
Author(s):  
YU.S. FILIMONOVA ◽  
◽  
E.G. VELICHKO ◽  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Power Plants ◽  
High Efficiency ◽  
Thermal Power ◽  
Thermal Power Plants ◽  
Complex Chemical ◽  
Composition And Structure ◽  
Combined Use ◽  
Mineral Additive

Modification of the composition and structure of heavy concrete with the use of a complex chemical-mineral additive consisting of fly ash from thermal power plants, a superplasticizer, a high-valence hardening accelerator AC and a fine-dispersed clinker component is considered. Modified concrete is characterized by an increase in compressive strength at a brand age by 67%, a decrease in the water content of a concrete mixture by 13.6% and an improvement in its workability by 11-12 cm. With the combined use of a superplasticizer and a high-valence hardening accelerator AC a significant synergistic effect is observed in the format of enhancing their plasticizing effect. The high efficiency of the application of the mixed-dispersed clinker component has been established.

scholarly journals Stabilization Study of a Contaminated Soil with Metal(loid)s Adding Different Low-Grade MgO Degrees

2020 ◽  
Vol 12 (18) ◽  
pp. 7340
Author(s):  
Jessica Giro-Paloma ◽  
Joan Formosa ◽  
Josep M Chimenos
Keyword(s):  
Contaminated Soil ◽  
Contaminated Soils ◽  
Low Grade ◽  
X Ray Diffraction ◽  
Optimal Stabilization ◽  
X Ray ◽  
Neutralization Capacity ◽  
Stabilizing Agents ◽  
Acid Test ◽  
By Products

Low-grade magnesium oxide (LG-MgO) was proposed as ordinary Portland cement (OPC) or lime substitute (CaO) for metal(loid)s remediation in contaminated soils. Some metal(loid)s precipitate at pH ≈ 9 in insoluble hydroxide form thus avoiding their leaching. LG-MgO avoids the re-dissolution of certain metal(loid)s at 9.0 < pH < 11.0 (pH-dependents), whose solubility depends on the pH. A highly contaminated soil with heavy metal(loid)s was stabilized using different LG-MgO by-products sources as stabilizing agents. Two of the three studied LG-MgOs were selected for the stabilization, by mixing 5, 10, and 15 wt.%. The effect of using LG-MgO not only depends on the size of the particles, but also on those impurities that are present in the LG-MgO samples. Particle size distribution, X-ray fluorescence (XRF), X-ray diffraction (XRD), thermogravimetric analysis, citric acid test, specific surface, bulk density, acid neutralization capacity, batch leaching tests (BLTs), and percolation column tests (PCTs) were techniques used to deeply characterize the different LG-MgO and the contaminated and remediated soils. The remediation’s results efficacy indicated that when the medium pH was between 9.0 and 11.0, the concentration of pH-dependent metal(loid)s decreases significantly. Although around 15 wt.% of a stabilizing agent was appropriate for the soil remediation to ensure an alkali reservoir that maintains optimal stabilization conditions for a long period, 5 wt.% of LG-MgO was enough to remedy the contaminated soil. When evaluating a polluted and decontaminated soil, both BLTs and PCTs should be complementary procedures.

scholarly journals Molecular Determinants of Substrate Recognition in Hematopoietic Protein-tyrosine Phosphatase

2004 ◽  
Vol 279 (50) ◽  
pp. 52150-52159 ◽  
Author(s):  
Zhonghui Huang ◽  
Bo Zhou ◽  
Zhong-Yin Zhang
Keyword(s):  
Substrate Specificity ◽  
Protein Tyrosine Phosphatase ◽  
Cellular Proliferation ◽  
High Efficiency ◽  
Tyrosine Phosphatase ◽  
Substrate Recognition ◽  
Fold Increase ◽  
Phosphoryl Transfer ◽  
Protein Tyrosine ◽  
Hydrolysis Of

The extracellular signal-regulated protein kinase 2 (ERK2) plays a central role in cellular proliferation and differentiation. Full activation of ERK2 requires dual phosphorylation of Thr183and Tyr185in the activation loop. Tyr185dephosphorylation by the hematopoietic protein-tyrosine phosphatase (HePTP) represents an important mechanism for down-regulating ERK2 activity. The bisphosphorylated ERK2 is a highly efficient substrate for HePTP with akcat/Kmof 2.6 × 106m–1s–1. In contrast, thekcatK/mvalues for the HePTP-catalyzed hydrolysis of Tyr(P) peptides are 3 orders of magnitude lower. To gain insight into the molecular basis for HePTP substrate specificity, we analyzed the effects of altering structural features unique to HePTP on the HePTP-catalyzed hydrolysis ofp-nitrophenyl phosphate, Tyr(P) peptides, and its physiological substrate ERK2. Our results suggest that substrate specificity is conferred upon HePTP by both negative and positive selections. To avoid nonspecific tyrosine dephosphorylation, HePTP employs Thr106in the substrate recognition loop as a key negative determinant to restrain its protein-tyrosine phosphatase activity. The extremely high efficiency and fidelity of ERK2 dephosphorylation by HePTP is achieved by a bipartite protein-protein interaction mechanism, in which docking interactions between the kinase interaction motif in HePTP and the common docking site in ERK2 promote the HePTP-catalyzed ERK2 dephosphorylation (∼20-fold increase inkcat/Km) by increasing the local substrate concentration, and second site interactions between the HePTP catalytic site and the ERK2 substrate-binding region enhance catalysis (∼20-fold increase inkcat/Km) by organizing the catalytic residues with respect to Tyr(P)185for optimal phosphoryl transfer.

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