Reductive acid leaching of cadmium from zinc neutral leaching residue using hydrazine sulfate

Zinc neutral leaching residue（ZNLR） from hydrometallurgical zinc smelting processing can be determined as hazardous intermediate containing considerable amounts of Cd and Zn which have great threats to the environment. The ZNLR contained approximately 35.99% Zn, 15.93% Fe and 0.26% Cd, and Cd mainly existed as ferrites in the ZNLR in this research. Reductive acid leaching of ZNLR was investigated. The effects of hydrazine sulfate concentration, initial sulfuric acid concentration, temperature, duration and liquid-to-solid ratio on the extraction of Cd, Zn and Fe were examined. The extraction efficiencies of Cd, Zn and Fe reached 90.81%, 95.83% and 94.19%, respectively when the leaching parameters were fixed as follows： hydrazine sulfate concentration, 33.3 g/L; sulfuric acid concentration, 80 g/L; temperature, 95 °C; duration of leaching, 120 min; liquid-to-solid ratio, 10 m L/g and agitation, 400 r/min. XRD and SEM-EDS analyses of the leaching residue confirmed that lead sulfate（Pb SO4） and hydrazinium zinc sulfate（（N2H5）2Zn（SO4）2） were the main phases remaining in the reductive leaching residue.

Process mineralogy characteristics of acid leaching residue produced in low-temperature roasting-acid leaching pretreatment process of refractory gold concentrates

To provide a theoretical basis for a suitable process to extract gold from refractory gold concentrates, process mineralogy on the acid leaching residue of gold calcine was studied by chemical composition, X-ray diffraction, scanning electron microscopy-energy spectrum, and mineral dissociation analysis. The results showed that the acid leaching residue contained Au 68.22 g/t, Ag 92.71 g/t, Fe 0.44%, As 0.10%, and S 0.55%. Gold and silver minerals existed as native gold, argentite, and proustite. Quartz, the main gangue mineral, accounted for 78.33 wt/%. The dissociation degree analysis showed that the proportions of monomer and exposed gold in acid leaching residue were 96.66 wt%. The cyanidation results showed that the cyanide gold leaching rate of acid leaching residues was close to 100 wt%. However, the maximum cyanide gold leaching rate of gold calcine was only 85.31 wt%. This suggests that acid leaching can increase the gold dissolution rate in the cyanide process.

Low-Molecular-Weight Aliphatic Acids in Soils Incubated with Plant Residues Under Different Moisture Conditions

Incubation experiments were conducted to investigate the dynamics of low- molecufar-weight aliphatic acids in two andosols with and without plant materials. Results showed that amount of low- molecular-weight aliphatic acids in soils alone varied considerably with water regime under which the soil was incubated,duration of incubation and soil organic matter content, ranging from 257-860 pmol kg-1 soil I of which 19%～33% was in free state. Incorporation of plant materials increased greatly both the amount and number of members of low- molecular- weight aliphaticacidst and also the proporticn of low-molec "far-weight aliphatic acids occurred in free state. Generally, among these aliphatic acids detected, acetic, propionic, glyoxalic and formic acids were predominant.

Leaching kinetics of acid-soluble Cr(Ⅵ) from chromite ore processing residue with hydrofluoric acid

Leaching kinetics of acid-soluble Cr（VI） in chromite ore processing residue （COPR） using hydrofluoric （HF） acid solution as a leaching agent was investigated for potential remediation of COPR with industrial waste water containing HF. The results show that HF can effectively destabilize the Cr（VI）-bearing minerals, resulting in the mobilization of Cr（VI） from COPR into the leachate. Particle size significantly influences the leaching of acid-soluble Cr（VI） from COPR, followed by leaching time, whereas the effects of HF concentration and leaching temperature are slight and the influence of stirring rate is negligible. The leaching process of acid-soluble Cr（VI） from COPR is controlled by the diffusion through the product layer. The apparent activation energy is 8.696 kJ/mol and the reaction orders with respect to HF concentration and particle size is 0.493 8 and -2.013 3, respectively.

Isolation of an acid producing Bacillus sp. EEEL02: Potential for bauxite residue neutralization

Bauxite residue deposit area(BRDA)is a typical abandoned mining wasteland representing extreme hostile environment with increased alkalinity.Microbially-driven neutralization of bauxite residue,based on the microbial acid producing metabolisms,is a novel strategy for achieving rapid pH neutralization and thus improving its environmental outcomes.The hypothesis was that these extreme conditions promote microbial communities which are capable of novel ecologically relevant functions.Several alkaliphilic acid producing bacteria were isolated in this study.One strain was selected for its superior growth pattern and acid metabolism(termed EEEL02).Based on the phylogenetic analysis,this strain was identified as Bacillus thuringiensis.The optimized fermentation conditions were as follows:pH 10;NaCl concentration 5%;temperature 25℃;EEEL02 preferred glucose and peptone as carbon and nitrogen sources,respectively.Based on optimal fermentation conditions,EEEL02 induced a significant pH reduction from 10.26 to 5.62 in 5-day incubation test.Acetic acid,propionic acid and CO2(g)were the major acid metabolites of fermentation,suggesting that the pH reduction in bauxite residue may be caused by acid neutralization derived from microbial metabolism.This finding provided the basis of a novel strategy for achieving rapid pH neutralization of bauxite residue.

Recycling of waste carbon residue from spent lithium-ion batteries via constant-pressure acid leaching

Waste carbon residue(WCR)was efficiently detoxicated and regenerated to high-purity graphite(PGC)used in lithium-ion batteries through the constant-pressure acid leaching technique.The leaching conditions were optimized by the combination of orthogonal and single-factor experiments.Results show that PGC with 99.5%purity is regenerated at temperature of 60℃,initial acid concentration of 12%,leaching time of 180 min,and liquid-to-solid ratio of 25:1,satisfying the requirements of commercial graphite.Meanwhile,the sodium hydroxide precipitation process was designed to recover valuable components from leachate efficiently.Ni,Co,Mn,and Al recoveries reach 96.92%,87.5%,97.83%,and 92.17%,respectively,at pH=11.Moreover,the co-product NaF can be recovered with purity over 99%via evaporative crystallization.The loss rate of fluorine is less than 0.5%,thereby eliminating the pollution risk of fluorine to the environment.The proposed process shows considerable environmental and economic benefits.

Improvement of alkaline electrochemical characteristics of bauxite residue amendment with organic acid and gypsum

Neutralization of alkaline properties of bauxite residue(BR)by using organic acid and gypsum additions may effectively improve electrochemical properties and alleviate physicochemical barriers to ecological rehabilitation.Mineral acids,citric acid and hybrid acid–gypsum additions were compared for their potential to transform and improve zeta potential,isoelectric point(IEP),surface protonation and active alkaline-OH groups,which are critical factors for further improvement of physicochemical and biological properties later.Isoelectric points of untransformed bauxite residue and six transformed derivatives were determined by using electroacoustic methods.Electrochemical characteristics were significantly improved by the amendments used,resulting in reduced IEP and-OH groups and decreased surface protonation for transformed residues.XRD results revealed that the primary alkaline minerals of cancrinite,calcite and grossular were transformed by the treatments.The treatments of citric acid and gypsum promoted the dissolution of cancrinite.From the SEM examination,citric acid and gypsum treatments contributed to the reduction in IEP and redistribution of-OH groups on particle surfaces.The collective evidence suggested that citric acid and gypsum amendments may be used firstly to rapidly amend bauxite residues for alleviating the caustic conditions prior to the consideration of soil formation in bauxite residue.

Critical Amino Acid Residues for Nicotine 5'-Hydroxylation in Human CYP2A Enzymes

Objective： We have continued previous work in which we demonstrated that #117 and #372 amino acids contributed to the high activities of human CYP2A13 in catalyzing 4-methylnitrosamino-1-（3-pyridyl）-1-butanone（NNK） and aflatoxin BI（AFB1） carcinogenic activation. The present study was designed to identify other potential amino acid residues that contribute to the different catalytic characteristics of two CYP2A enzymes, CYP2A6 and CYP2A13, in nicotine metabolism and provide insights of the substrate and related amino acid residues interactions. Methods： A series of reciprocally substituted mutants of CYP2A6lle^300→ Phe, CYP2A6Gly^301aAla, CYP2A6Ser^369 → Gly, CYP2A13Phe^300→ Ile, CYP2A13Ala^301 → Gly and CYP2A13Gly^369 → Set were generated by site-directed mutagenesis/baculovirus-Sf9 insect cells expression. Comparative kinetic analysis of nicotine 5＇hydroxylatin by wild type and mutant CYP2A proteins was performed. Results：All amino acid residue substitutions at 300, 301 and 369 caused significant kinetic property changes in nicotine metabolism. While CYP2A6Ile^300→ Phe and CYP2A6Gly^301→Ala mutations had notable catalytic efficiency increases compared to that for the wild type CYP2A6, CYP2A13Phe^300→Ile and CYP2A13Ala^301→Gly replacement introduced remarkable catalytic efficiency decreases. In addition, all these catalytic efficiency alterations were caused by Vmax variations rather than Km changes. Substitution of #369 residue significantly affected both Km and Vmax values. CYP2A6Ser^369 → Gly increase the catalytic efficiency via a significant Km decrease versus Vmax enhancement, while the opposite effects were seen with CYP2A13Gly^369 → Ser. Conclusion：#300, #301 and #369 residues in human CYP2A6/13 play important roles in nicotine 5＇ -oxidation. Switching #300 or #301 residues did not affect the CYP2A protein affinities toward nicotine, although these amino acids are located in the active center. Set369 to Gly substitution indirectly affected nicotine binding by creating more space and conformational flexibility for the nearby residues, such as Leu^370 which is crucial for many hydroxylations.

Extraction and Characterization of Biological Humic Acids from Fermented Furfural Residue

Objective] This study aimed to eliminate the negative effects brought about by continuous, long-term accumulation of sodium ions in soil on soil environ-ment. [Method] Biological humic acids （BHAs） were extracted from fermented furfural residue via alkali-dissolution and acidification. The effects of solid-liquid ratio （mass ratio of fermented furfural residue to water）, alkali concentration, extraction tempera-ture and extraction time on the content of BHA were investigated. Also its structure was characterized by FTIR. [Result] The optimal extraction conditions were as fol-lows： solid-liquid ratio of 1：7, KOH concentration of 6%, extraction temperature of 70℃ and extraction time of 1 h. Under the optimal conditions, the content of BHAs extracted was up to 8.5%. The infrared spectrum analysis indicated that BHA had more types of functional groups and lower molecular weight than commercial humic acid although they had similar structures. [Conclusion] The technique has the ad-vantages of simple operation and good stability, and is suitable for extracting BHAs. BHAs have a good prospect in developing new types of humic acid fertilizers.

Constructing a stable interface on Ni-rich LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode via lactic acid-assisted engineering strategy

Ni-rich layered oxides are potential cathode materials for next-generation high energy density Li-ion batteries due to their high capacity and low cost.However,the inherently unstable surface properties,including high levels of residual Li compounds,dissolution of transition metal cations,and parasitic side reactions,have not been effectively addressed,leading to significant degradation in their electrochemical performance.In this study,we propose a simple and effective lactic acid-assisted interface engineering strategy to regulate the surface chemistry and properties of Ni-rich LiNi_(0.8)Co_(0.1)Mr_(0.1)O_(2) cathode.This novel surface treatment method successfully eliminates surface residual Li compounds,inhibits structural collapse,and mitigates cathode-electrolyte interface film growth.As a result,the lactic acidtreated LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) achieved a remarkable capacity retention of 91.7% after 100 cycles at 0.5 C(25℃) and outstanding rate capability of 149.5 mA h g^(-1) at 10 C,significantly outperforming the pristine material.Furthermore,a pouch-type full cell incorporating the modified LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode demonstrates impressive long-term cycle life,retaining 81.5% of its capacity after 500 cycles at 1 C.More importantly,the thermal stability of the modified cathode is also dramatically improved.This study offers a valuable surface modification strategy for enhancing the overall performance of Ni-rich cathode materials.

Effect of Dodecylbenzene Sulfonic Acid Used as Additive on Residue Hydrotreating

The effect of additive—dodecylbenzene sulfonic acid(DBSA)—on residue hydrotreating was studied in the au toclave. The results showed that the additive improved stabilization of the colloid system of residue, which could delay th aggregation and coke formation from asphaltenes on the catalyst, and make heavy components transformed into light oi The residue conversion in the presence of this additive increased by 1.94%, and the yield of light oil increased by 1.53%when the reaction time was 90 min. The surface properties of the catalyst in the presence of this additive were better tha that of the blank test within a very short time(30 min) and deteriorated rapidly after a longer reaction time due to highe conversion and coke deposition. Compared with the blank test, the case using the said additive had shown that the structur of hydrotreated asphaltene units was smaller and the condensation degrees were higher. The test results indicated that th additive could improve the hydrotreating reactivity of residue via permeation and depolymerization, the heavier componen could be transformed into light oil more easily, and the light oil yield and residue conversion were higher for the case usin the said additive in residue hydrotreating process.

Development on the Technique of Total Recovery of Benzoic Acid Residue

Benzoic acid residue is solid waste produced from the production of benzoic acid by oxidizing toluene.Because it contained important chemical raw materials such as benzoic acid,benzyl benzoate and fluorenone,it is necessary to recover them from the residue.In this work the technique featured with high efficiency evaporation and vacuum distillation was developed to obtain total recovery and utilization of the benzoic acid residue.By controlling the operation temperature at 260℃ and the pressure of 16kPa in the rising and falling film evaporators,heavy components separated efficiently from the residue can be polymerized and the light components consisting of 63% of the residue entered into a benzoic acid vacuum distillation column.Keeping the temperature of polymerization at(280±10)℃,coumarone resin was produced after adjusting the softening point according to the market requirements.Vacuum distillation was operated under the following conditions:top temperature at 186℃,top pressure of 16kPa,bottom temperature at 240-250℃,reflux ratio being 3︰1.Benzoic acid of 98% purity was distilled out from the column as a side stream and the bottom product was crude benzyl benzoate.By the developed technique,the benzoic acid residue was splitted into three products,benzoic acid,crude benzyl benzoate and coumarone resin without any surplus waste.

Separation of Benzoic Acid Residue by Flash-Vacuum Distillation-Melt Crystallization

A large amount of residue including benzoic acid, benzyl benzoate and fluorenone can form in the production of benzoic acid by oxidizing toluene. To recycle the resources and reduce secondary pollution, the treatment of benzoic acid residue was carried out to obtain the three purified materials by flash-vacuum distillation combination method, and the influence of the operating parameters, such as the top pressure, reflux ratio and top and bottom temperatures was investigated to obtain the best operating conditions. The experimental results show that the benzoic acid purity can reach 97% through distillation under the following conditions： the top pressure is 1 600 Pa, the bottom temperature is 190--200℃, the top temperature is 130--135℃, and reflux ratio is 5：1. The best operating conditions for benzyl benzoate distillation column are： the top pressure is 400 Pa, bottom temperature is 250-- 260 ℃, the top temperature is 150--160 , and reflux ratio is 5：1. The benzyl benzoate purity can reach 95%, and the fiuorenone purity can reach 92 %. When refined by melt crystallization, the benzoic acid purity can be improved up to 99.6%, and the purities of benzyl benzoate and fluorenone are both above 95%.

Favorable and unfavorable amino acid residues in water-soluble and transmembrane proteins

We analyzed the amino acid residues present in the water-soluble and transmembrane proteins of 6 thermophilic and 6 mesophilic species of the domains Archaea and Eubacteria, and characterized them as favorable or unfavorable. The characterization was performed by comparing the observed number of each amino acid residue to the expected number calculated from the percentage of nucleotides present in each gene. Amino acids that were more or less abundant than expected were considered as favorable or unfavorable, respectively. Comparisons of amino acid compositions indicated that the water-soluble proteins were rich in charged residues such as Glu, Asp, Lys, and His, whereas hydrophobic residues such as Trp, Phe, and Leu were abundant in transmembrane proteins. Interestingly, our results found that although the Trp residue was abundant in transmembrane proteins, it was not defined as favorable by our calculations, indicating that increased numbers of a particular amino acid does not necessary indicate it is a favorable residue. Amino acids with high G + C content such as Ala, Gly, and Pro were frequently observed as favorable in species with low G + C content. Comparatively, amino acids with low G + C content such as Phe, Tyr, Lys, Ile, and Met were frequently observed as favorable in species with high G + C content. These are the examples to increase the supply of amino acids than expected. Amino acids with neutral G + C content, i.e., Glu and Asp were favorable in water-soluble proteins from all species analyzed, and Cys was unfavorable both in water-soluble and transmembrane proteins. These results indicate that amino acid compositions are essentially determined by the nucleotide sequence of the genes, and the amino acid content is altered by a deviation from expectation.

Study on Extraction of Biological Humic Acids from Fermented Furfural Residue

[Objective] This study was conducted to obtain the optimal process for the preparation of biological humic acids （BHAs） from fermented furfural residue by al- kali-dissolution and acidification. [Method] BHAs were extracted from fermented furfural residue by the alkali-dissolution and acidification method, to investigate the effects of solid-liquid ratio （mass ratio of fermented furfural residue to water）, alkali concentration, extraction temperature and extraction time on the extraction rate of BHAs by an orthogonal experiment, and then a solid BHA product was obtained by acidification of its extract followed by solid-liquid separation and oven-drying. [Result] The results showed that the optimal extracting conditions were as follows： solid-liquid ratio of 1：8, alkali concentration of 8% KOH, with extracting temperature at 70℃ and extracting time of 2.5 h in the alkali-dissolution step, and in the acidification step, the pH of the BHA mixture was 2.5. Under the optimal conditions, the content of solid BHAs was 76%, and the extraction rate of BHAs was 49%. [Conclusion] This study provides a theoretical basis for the separation and purification of BHAs from fermented furfural residue by the alkali dissolution and acidification method.

Effects of β-Amino Butyric Acid Induced Rice Blast Resistance on Reactive Oxygen Metabolism

[Objective] This study was to understand the effects of β-Amino butyric acid(abbreviated as BABA) induced rice blast resistance on reactive oxygen metabolism. [Method] Using the cultivar Chaochan 2 that is highly susceptible to disease as experimental material, the changes of catalase(CAT), and superoxide dismutase(SOD) and MDA activities in rice treated by BABA were investigated. [Result] In rice plants treated by BABA, the activities of CAT and SOD increased, meanwhile the MDA content also rose to some extent, resulting in the disease resistance to rice blast. [Conclusion] By influencing reactive oxygen metabolism, BABA endows rice plants with resistance to rice blast. BABA is safe to environment and has highly resistance-inducing capacity, it could be generalized in production.

Valorisation of industrial hemp (Cannabis sativa L.) residues and cheese whey into volatile fatty acids for single cell protein production

The production of single cell protein(SCP)using lignocellulosic materials stands out as a promising route in the circular bioeconomy transition.However,multiple steps are necessary for lignocellulosics-to-SCP processes,involving chemical pretreatments and specific aerobic cultures.Whereas there are no studies that investigated the SCP production from lignocellulosics by using only biological processes and microbial biomass able to work both anaerobically and aerobically.In this view,the valorisation of industrial hemp(Cannabis sativa L.)biomass residues(HBRs),specifically hurds and a mix of leaves and inflorescences,combined with cheese whey(CW)was investigated through a semi-continuous acidogenic co-fermentation process(co-AF).The aim of this study was to maximise HBRs conversion into VFAs to be further used as carbon-rich substrates for SCP production.Different process conditions were tested by either removing CW or increasing the amount of HBRs in terms of VS(i.e.,two and four times)to evaluate the performance of the co-AF process.Increasing HBRs resulted in a proportional increase in VFA production up to 3115 mg HAc L^(-1),with experimental production nearly 40%higher than theoretical predictions.The synergy between HBRs and CW was demonstrated,proving the latter as essential to improve the biodegradability of the former.The produced VFAs were subsequently tested as substrates for SCP synthesis in batch aerobic tests.A biomass concentration of 2.43 g TSS L^(-1) was achieved with a C/N ratio of 5.0 and a pH of 9.0 after two days of aerobic fermentation,reaching a protein content of 42%(g protein per g TSS).These results demonstrate the overall feasibility of the VFA-mediated HBR-to-SCP valorisation process.

Syntheses and Structural Characterization of Dimethyltin Complexs of N-(3-Methoxysalicylidene)-α-amino Acid

Three new dimethyltin complexes of N-（3-methoxysalicylidene）-α-amino acid,（CH3）2Sn（3-CH3O-2-OC6H3CH=NCHRCOO）（R = H,1;CH3,2;（CH3）2CH,3）,have been synthe-sized by treating dimethyltin dichloride with the potassium salt of the ligand and characterized by elemental analysis,IR and 1H NMR spectra.The crystal structure of [（CH3）2Sn（3-CH3O-2-OC6H3CH=NCH2COO）（CH3OH）]2 H2O（1a）,formed from methanol solution of 1,has been deter-mined.The crystal belongs to the monoclinic system,space group C/2c with a = 20.636（3）,b = 7.8854（9）,c = 20.668（2） ,β= 113.265（2）°,V = 3089.7（6） 3,Z = 4,Dc = 1.707 g/cm3,= 1.675 mm-1,F（000） = 1592,R = 0.0301 and wR = 0.0841.In complex 1a,the tin atom is six-coordinate and possesses a distorted [SnC2NO3] octahedral geometry with the two methyl groups occupying the trans positions.The weak Sn O interactions and intermolecular hydrogen bonds connected the molecules into an infinite chain.

Antioxidation and active constituents analysis of flower residue of Rosa Damascena Mill

OBJECTIVE To make full of resource,the bioactivity and active constituent analysis were firstly system⁃atically investigated on damask rose flower residue(DRFR).METHODS DPPH and ABTS experiments were applied to assess the antioxidant activity of DRFR.Then,column chromatography was used to purify compounds from DRFR-A,and the chemical structure was identified using nuclear magnetic resonance(NMR).The total phenolic acid content was measured by folin-ciocalteu colorimetric method and the content of gallic acid the indicator ingredient,was detected by high performance liquid chromatography(HPLC).RESULTS By DPPH and ABTS experiments,an antioxidation extract(DRFR-A)was found and displayed a high activity both on DPPH(IC50:2.760 mg·L^-1)and ABTS(IC50:2.258 mg·L^-1)compared to positive control VC.Ten compounds were isolated and identified from DRFR-A,and the most are phenolic acids.Among them,pyrogallic acid,2-phenylethyl-3,4,5-trihydroxybenzoate,p-hydroxybenzoic acid and p-hydroxy⁃phenethyl alcohol were obtained from the plant for the first time.The content of total phenolic acids and main ingredient,gallic acid,in DRFR-A was determined as 63.73%and 5.12%,respectively.CONCLUSION This study provides reliable science data and lays the foundation for the development and utilization of rose residue,and hence for the full utilization of rose resources.