Oxidative Pretreatment Research Articles

Structural evolution after oxidative pretreatment and CO oxidation of Au nanoclusters with different ligand shell composition: a view on the Au core.

The reactivity of supported monolayer protected Au nanoclusters is directly affected by their structural dynamics under pretreatment and reaction conditions. The effect of different types of ligands of Au clusters supported on CeO2 on their core structure evolution, under oxidative pretreatment and CO oxidation reaction, was investigated. X-ray absorption and X-ray photoelectron spectroscopy studies revealed that the clusters evolve to a similar core structure above 250 °C in all the cases, indicating the active role of the ligand-support interaction in the reaction.

Insights into the recent advances in the pretreatment of biomass for sustainable bioenergy and bio-products synthesis: Challenges and future directions

Recently, biomass has shown its viability as an alternative to fossil fuels. Due to the growing trend in greenhouse gas emissions generated by the continual burning of fossil fuel products, it will be advantageous for humanity to seek a more sustainable and renewable source of energy. Due to its availability, biomass has a promising approach as a feedstock for bioconversion processes that produce energy, fuels, and other chemicals. The carbon dioxide generated by burning biomass has no influence on atmospheric carbon dioxide since it is derived from a renewable source. Despite these benefits, its adoption in bioconversion and biorefinery processes has traditionally been hindered by its recalcitrant nature, as indicated by its intrinsic characteristics. Prior to any conversion process, biomass must be pretreated to enhance product recovery. To satisfy the rising need for renewable and sustainable energy sources, the present conversion efficiency must be improved and the biorefinery concept must transition from using just one biomass component (cellulose) to utilizing the complete biomass component. This study examines numerous pretreatment procedures used prior to any conversion process, the challenges faced, and the future of biomass pretreatment technologies. Physical, hydrothermal, chemical, oxidation, biological, and hybrid pretreatment techniques are evaluated. The review indicates that the ideal approach to biomass pretreatment must be able to deal with the recalcitrant nature of biomass, enhance the crystallinity of cellulose, and provide the greatest recovery of biofuels, bio-char, sugars, and other industrially relevant bioproducts. The data offered in this study will equip readers with the knowledge necessary to effectively identify solutions to pretreatment problems and energy generation from pretreated biomass.

Treatment of emerging contaminants in simulated wastewater via tandem photo-Fenton-like reaction and nutrient recovery

Nutrient rich wastewater containing emerging organic contaminants was used for struvite synthesis with a novel tandem process with a heterogeneous Fenton oxidation pretreatment.

Co-treatment of landfill leachate with urban wastewater by chemical, physical and biological processes: Fenton oxidation preserves autochthonous bacterial community in the activated sludge process

The impact of Fenton oxidation (FO) and Air stripping (AS) pre-treatments on the bacterial community of a biological activated sludge (B-AS) process for the co-treatment of mature landfill leachate (MLL) and urban wastewater (UWW) was assessed. In this work high-throughput sequencing was used to identify changes in the composition of the bacterial communities when exposed to different landfill leachate's pre-treatments. The combination of FO and AS to increase biodegradability (BOD5/COD) and reduce ammonia concentration (NH3) respectively, allowed to successfully operate the B-AS and effectively treat MLL. In particular, BOD5/COD resulted to be the key factor for bacterial community shifting. The microbiological community of the B-AS, mainly composed by the phylum Bacteroidota (Saprospiraceae, PHOS-HE51, Chitinophagaceae) after FO pre-treatment, shifted to Pseudomonadota (Caulobacteraceae and Hyphomicrobiaceae) when FO was not used. At the same time a drastic reduction in BOD5 removal was observed (90%–58%). On the other hand, high NH3 concentration affected the abundance of the family Saprospiraceae, known to play a key role in the degradation of complex organic compounds in B-AS. The results obtained suggest that a suitable combination of pre-treatments can reduce the negative effect of MLL on the B-AS process, reducing the pressure on autochthonous bacteria and therefore the acclimatization time of the biological process.

Mitigation of ultrafiltration membrane fouling by a simulated sunlight-peroxymonosulfate system with the assistance of irradiated NOM

Oxidation pretreatments prior to ultrafiltration are hindered by the need for energy input and sludge disposal. Herein, a simulated sunlight-induced natural organic matter (NOM) for peroxymonosulfate (PMS) activation was used as pretreatment to alleviate ultrafiltration membrane fouling caused by NOM itself in the Songhua River water. When light intensity was over 100 mW/cm2, the pretreatment removed NOM effectively, characterized with UV254, dissolved organic carbon (DOC) and maximum fluorescent intensity (Fmax), and improved filtration flux. At 200 mW/cm2 light intensity and 0.5 mM PMS, 57.5% of UV254 and 18.5% of DOC were removed, and humic-like fluorescent component was degraded by 84%-94% while ∼60% for protein-like substance. Membrane flux was increased by 94%, and reversible and irreversible fouling resistances were reduced by 62.4% and 51.9%, respectively. Both total fouling index (TFI) and hydraulic irreversible fouling index (HIFI) were moderately correlated with the DOC, whereas they prominently correlated with the UV254 and the Fmaxs of all fluorescence components, which could be served as key indicators to predict and control membrane fouling. Mathematical modeling showed that the pretreatment alleviated the fouling in the membrane pores and cake layer. The simulated sunlight-induced NOM (3NOM* and eaq¯) could activate PMS to form active species, which enabled to oxidize high molecular weight (MW) substances and mineralize low MW compounds in NOM as well as hinder their linking with inorganic cations, thereby reducing organic and inorganic membrane fouling simultaneously. This study may provide a new strategy for decentralized potable water treatment, especially in a single household or community.

Direct electroseparation of zinc from zinc sulfide in eco-friendly deep eutectic solvent: Highlighting the role of malonic acid

Zinc sulfide (ZnS), one of the main ingredients of zinc ore and emerging materials, partly processes environmental risk. Deep eutectic solvents (DESs) are green solvents to efficiently separate metals with less emission. In this study, a novel route for direct electroseparation of Zn from ZnS in eco-friendly choline chloride-urea DES with the addition of malonic acid (MA) is studied for the first time. The role of MA and the reduction behavior of Zn(II) are systematically analyzed by cyclic voltammetry. The reduction of Zn(II) is quasi-reversible and follows one-step two-electron transfer process. Pure Zn with nanostructure is obtained with the current efficiency of 86.5 % and energy consumption of 2621.8 kW·h·t−1 at the optimized parameters of 10 mA·cm−2, 353 K and 100 mM·L-1 ZnS. Mechanisms analyses indicate that in the presence of 60 mM·L-1 MA, besides [ZnCl−3]- and [ZnCl−5]3-, some ZnS are dissolved to form stable [Zn(MA)2-Cl−2]4-, [Zn(MA)2-Cl-]3- and other MA based ligands, which causes a higher Zn ion solubility of 0.13 mol·L-1 and may promote the subsequent electroseparation of ZnS. Results from this study are expected to propose a simplified route to directly separate Zn from ZnS without oxidation pretreatment to achieve hazardous waste minimization.

Effects of Fe(II)-activated persulfate/sodium percarbonate (PS/SPC) pretreatment on ultrafiltration membrane fouling control and mechanisms

Membrane fouling during the ultrafiltration (UF) is a key restricting factor in the treatment of drinking water. To control membrane fouling, a ferric ion activated dual oxidant (persulfate/sodium percarbonate (PS/SPC)) pretreatment method was employed to degrade natural organic matter (NOM) in drinking water sources. In this work, the quantity and properties of NOM in water sample before and after the Fe(II)/persulfate/sodium percarbonate(Fe(II)/PS/SPC) oxidation pretreatment were evaluated, and the changes in the morphology of the membrane and the accumulation characteristics of organic functional groups in the fouling on the membrane surface were analysed. The oxidation efficiency of system was compared by taking bisphenol A as the target pollutant, which is an important basis for its superior NOM removal compared with conventional treatment system. More importantly, adding part of SPC to the system while reducing the amount of PS can effectively solve the issue of pH reduction caused by PS decomposition. The extended Derjaguin–Landau–Verwey–Overbeek (xDLVO) theory analysed that with the relative increase in pH value, the Lewis acid-base interaction energy decreases, which is also the reason for the decline in irreversible pollution. The results showed that Fe(II) activated double oxidant (PS/SPC) pretreatment has a promising application in membrane fouling control.

Effective soil washing for Cu removal in industrial soil remediation

ABSTRACT Soil contamination caused by heavy metals has become a serious environmental and health-related problem to human. Copper (Cu) is essential to human and plants in appropriate amount but toxicant if excessive. Although soil washing has been developed for a long time for heavy metal remediation, there are few studies focusing on Cu, especially in the case of extreme concentration of metal and dissolved organic matters (DOM). Thus, based on the literature reviews about soil washing, this study tried to find out the practical and effective methods to achieve remediation for Cu pollution in different situations of various soil texture and pollution concentrations. Different Cu polluted soils in industrial ground were sampled in Shanghai for experiments. Considering washing agents, washing duration time, liquid to solid ratio, combinations of different agents and oxidation pretreatment, the optimal soil washing conditions were decided. Results showed that washing agents and soil texture seriously affected the efficiency of soil washing. 0.05 mol/L Ethylenediamine tetraacetic acid (EDTA) or 0.1 mol/L FeCl3 combined with 0.1 mol/L citric acid (CA) was valid for Cu washing for three different soils with removal rate ranged from 68.8 ± 0.8% to 83.2 ± 1.1%. Oxidation pretreatment was necessary when DOM was in high concentration.

Hydrocarbons removal and microbial community succession in petroleum-contaminated soil under hydrogen peroxide treatment.

Chemical oxidation as a pretreatment step coupled with bioremediation for petroleum-contaminated soil may pose serious impacts on indigenous microorganisms and the available nutrients. Petroleum-contaminated soil were treated by hydrogen peroxide (H2O2) at initial concentrations of 105mM (HH), 21mM (HL), and 105mM in three equal amounts (HT) without adding any external catalyst. The contents of total petroleum hydrocarbons (TPH) and dissolved nutrients (total organic compounds, nitrogen, and phosphate), and the indigenous bacteria community succession (analyzed by high-throughput sequencing of 16S rDNA) were investigated over 50days. Compared to the control treatment without H2O2 addition, H2O2 treatments for the petroleum-contaminated soil significantly promoted the TPH removal especially in the first 4days and impacted the contents of dissolved nutrients. Both of chemical oxidation and nutrients contributed to microbial community structure changes in alpha diversity. Although the soil microbial community structure had undergone significant changes after different chemical oxidation pretreatments, Firmicutes, Proteobacteria, Gemmatimonadetes, and Actinobacteria were the main bacterial phyla. Compared with adding H2O2 at one time, H2O2 added in stepwise was beneficial to indigenous bacterial diversity recovery and TPH removal. H2O2 oxidation treatments showed a great influence on the microbial community structures in the start-up stage, while recovery time rather than the oxidation treatments presented greater effects on the composition of the microbial community structure with the incubation time extended. Therefore, adding H2O2 as pretreatment for petroleum-contaminated soil showed little effect on the structure of soil indigenous microbial community from a long-term scale, and was conducive to the continuous removal of TPH by indigenous microorganisms.

Testing the effect of oxidizing pre-treatments on amino acids in benthic and planktic foraminifera tests

Amino acid racemization (AAR) is a geochronological method that uses the ratio of D- to L-configurations in optically active amino acids from carbonate fossils to determine the time elapsed since the death of an organism. Although AAR techniques have been widely applied to foraminiferal tests, there have been limited dedicated assessments of the potential of isolating a bleach-resistant, intra-crystalline fraction of proteins to improve the reliability of AAR in this biomineral system. In this study, we evaluate the effect of two oxidative pre-treatments (hydrogen peroxide and bleach) on amino acid concentrations and D/L values in sub-modern benthic foraminifers ( Ammonia spp. and Haynesina germanica ) and well-preserved mid Holocene and mid Pleistocene planktic foraminifers ( Pulleniatina obliquiloculata , Globorotalia truncatulinoides , and Globorotalia tumida ). The oxidative pre-treatments successfully reduced the amino acid content of the foraminiferal tests to a residual fraction, and with the exception of Ammonia spp., neither pre-treatment substantially affected the relative proportion of individual amino acids. The bleaching pre-treatment does not consistently alter D/L values when compared to peroxide pre-treatment, but it does tend to reduce the subsample variability in D/L values, albeit only to a small degree in an inconsistent fashion. Therefore, we recommend that a relatively weak oxidative pre-treatment with 3% hydrogen peroxide is sufficient for foraminifera-based AAR applications. • Intra-crystalline fraction of amino acids in foraminiferal tests was isolated using oxidative pre-treatments • Difference in concentration between the inter- and intra-crystalline fractions of amino acids decreases with increased sample age • No consistent improvement in intra-sample variability when foraminiferal tests are treated with bleach • Pretreating foraminiferal tests with peroxide rather than bleach is recommended

Quantitative comparison of the delignification performance of lignocellulosic biomass pretreatment technologies for enzymatic saccharification.

Pretreatments for delignification are required for the enzymatic saccharification of lignocellulosic biomasses. However, in the current literature, various pretreatment approaches have been applied for the same kinds of biomass. To find the optimum pretreatments for biomaterials containing various lignin contents, in this study, a quantitative comparison was carried out on the delignification performance of 15 categories of pretreatments. In total, 1729 sets of biomass, cellulose, hemicellulose, and lignin recovery data were collected from 214 relevant studies. Box plots and Cate-Nelson-like graphs were applied for analyses. The results showed that alkali, oxidation, organic solvent, and multistep pretreatments generally were better at removing lignin and recovering cellulose. Moreover, among these four categories, alkali pretreatments had the best performance, increasing the saccharification efficiency by approximately five-fold. Considering both delignification performance and saccharification improvement, alkali pretreatments are currently considered to be the optimum pretreatment methods for enzymatic saccharification.

The enhanced antibacterial effect of BNNS_Van@CS/MAO coating on Mg alloy for orthopedic applications

The development of multifunctional Mg-based active implants with controllable degradation and antibacterial capabilities has become a hotspot in the research field of biodegradable metallic materials. To this end, a BN nanosheets (BNNS) _vancomycin (Van) @chitosan (CS) nanocomposite coating containing two antibacterial components (BNNS and Van) was prepared on Mg alloys via a micro-arc oxidation (MAO) pre-treatment combined with following electrodeposition. The related characterizations of the coating show that the composite coating has a high roughness, hydrophobicity and fair corrosion resistance. In vitro antibacterial experiments show that the BNNS_Van@CS/MAO composite coating have obvious inhibitory effect on the growth of both E. coli and S. aureus. The antibacterial effect of the BNNS_Van@CS/MAO composite coating was attributed to the synergistic effect of CS, BNNS and Van. This study provides a valuable surface modification strategy for developing multifunctional Mg-based implants with good corrosion resistance and antibacterial properties.

Pd-Ce-Ox/MWCNTs and Pt-Ce-Ox/MWCNTs Composite Materials: Morphology, Microstructure, and Catalytic Properties.

The composite nanomaterials based on noble metals, reducible oxides, and nanostructured carbon are considered to be perspective catalysts for many useful reactions. In the present work, multi-walled carbon nanotubes (MWCNTs) were used for the preparation of Pd-Ce-Ox/MWCNTs and Pt-Ce-Ox/MWCNTs catalysts comprising the active components (6 wt%Pd, 6 wt%Pt, 20 wt%CeO2) as highly dispersed nanoparticles, clusters, and single atoms. The application of X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) provided analysis of the samples' morphology and structure at the atomic level. For Pd-Ce-Ox/MWCNTs samples, the formation of PdO nanoparticles with an average crystallite size of ~8 nm was shown. Pt-Ce-Ox/MWCNTs catalysts comprised single Pt2+ ions and PtOx clusters less than 1 nm. A comparison of the catalytic properties of the samples showed higher activity of Pd-based catalysts in CO and CH4 oxidation reactions in a low-temperature range (T50 = 100 °C and T50 = 295 °C, respectively). However, oxidative pretreatment of the samples resulted in a remarkable enhancement of CO oxidation activity of Pt-Ce-Ox/MWCNTs catalyst at T < 20 °C (33% of CO conversion at T = 0 °C), while no changes were detected for the Pd-Ce-Ox/MWCNTs sample. The revealed catalytic effect was discussed in terms of the capability of the Pt-Ce-Ox/MWCNTs system to form unique PtOx clusters providing high catalytic activity in low-temperature CO oxidation.

Controlling the formation of halogenated byproducts in the chlorination of source waters by oxidative pre-treatment with the Fe(II)/Fe(III)-S(IV)-air system.

Breakpoint chlorination is a generally accepted method for removing ammonium ion from source waters in drinking water treatment technologies. This process is often accompanied by the formation of halogenated organic byproducts. The presence of these compounds in potable water is of primary concern. In this paper, we demonstrate that the concentration of the precursors of the halogenated species can sufficiently be decreased by oxidizing the organic pollutants with the Fe(II)/Fe(III) - S(IV) - air system. Pre-oxidative treatment of the source waters results in a substantial reduction of chemical oxygen demand, while the ammonium ion concentration remains unaffected. The breakpoint chlorination produces substantially less trihalomethanes (THMs) and adsorbable halogenated organic compounds (AOXs) in oxidatively pre-treated source waters than in raw waters. These results offer a possibility to improve drinking water treatment technologies for better controlling the formation of antagonistic byproducts. It is demonstrated that reaching the regulated concentration levels of THMs is feasible with this method even in source waters containing organic pollutants at relatively high concentration levels. The main advantage of the procedure is that the reagents used for the oxidative pre-treatment are converted into non-toxic products (Fe(III) and SO42-) by the end of the process.

Impact of pre-treatments on the surface composition, the optical and flow properties of a CuCrZr powder dedicated to laser powder bed fusion use

Laser Powder Bed Fusion is not power efficient at processing copper‑chromium‑zirconium alloy due to the high reflectivity of the powder at the laser standard wavelength (1070 nm). A way to reduce the optical reflectivity is to modify the powder surface. This work aims to study the impact of reduction and oxidation pre-treatments on the surface chemistry of the particles, and to understand their consequences on the powder properties. X-ray photoelectron spectroscopy analyses show that, starting from a 2–3 nm thick native Cu 2 O layer, a wet atmosphere leads to the formation of a 54 nm thick Cu 2 O layer, whereas a reduction under hydrogen leads to pure copper. Under argon, the Cu 2 O thickness slightly increases up to 3–4 nm. The oxidation and the reduction treatments improve the flowability, respectively, by 46% and 26%. The reduction increases the reflectivity by 2%, whereas the oxidation reduces it by 26%. • Humid atmosphere leads to a strong increase of Cu 2 O layer thickness (2–3 to 54 nm) • Reduction under H 2 leads to a pure copper surface decorated with Cr and Zr oxides • Argon atmosphere gives a slight increase of Cu 2 O layer thickness (2–3 to 3–4 nm) • Positive impact of the oxidation and the reduction treatments on powder flowability • Correlation observed between oxide layer thickness and optical reflectivity of powder

Biodegradation of oxidized high-density polyethylene and oxo-degradable plastic using microalgae Dunaliella salina

ABSTRACT This research aimed to evaluate the effectiveness of microalgae Dunaliella salina in the biodegradation process of oxidized oxium and HDPE plastics. Microalgae and microplastic interactions were evaluated in two 1 L glass bioreactors containing D. salina with oxium microplastics and oxidized HDPE at various concentrations (100 mg/500 mL, 200 mg/500 mL, and 300 mg/500 mL) for 15 d. The results showed a more significant decrease in alkene functional groups in oxium plastics than in HDPE. In addition, there was a change in the oxium functional group with the formation of carbonyl, ether, and primary alcohol. The growth rate of D. salina decreased significantly after interaction with oxidized HDPE microplastics compared to oxium interaction. We established that oxium plastics have a faster biodegradation ability owing to the addition of additives to the plastic. However, oxidation pre-treatment with H2O2 on HDPE plastic can also accelerate the plastic degradation process.

Separation of copper-sulfur using sodium polyacrylate as pyrite depressant in acidic pulp: Floatability and adsorption studies

This study aimed to investigate the suitability of sodium polyacrylate (PAAS) as a pyrite depressant in a Cu-S separation system through flotation and adsorption experiments. Micro-flotation tests showed that chalcopyrite was selectively separated from pyrite using PAAS as a pyrite depressant in the pH range 2–4. A satisfactory separation effect, a copper concentrate with 30.02% Cu and a recovery of 94.16% was obtained in artificial mixed minerals tests. Adsorption studies showed that PAAS selectively adsorbed on pyrite in the pH range 2–4, while the adsorption on chalcopyrite was weaker, about 6.6 times lower than that on pyrite. PAAS adsorption on pyrite occurred through the interaction between (R-COO−)n and Fe(OH)n(3−n)+ at the solid/liquid interface. Oxidation pretreatment promoted the adsorption of Fe(OH)n(3−n)+ on pyrite, thus providing additional adsorption sites for PAAS and enhancing the adsorption of PAAS on pyrite. After PAAS adsorption, the weak floatability of pyrite in the presence of xanthate was due to the strong hydrophilicity imparted to pyrite by PAAS rather than hindering xanthate adsorption on pyrite.

Enhanced redox catalysis of electrochemical alcohol oxidation in alkaline medium by using Pt-Cu/C catalyst

In electrochemical alcohol oxidation reactions catalysed by supported Pt-based nanoparticles, the catalytic performance is highly correlated with the electron density accumulated over the metal’s surface. The highly electronegative nature of Pt, affects the catalytic performance by accumulating electrons generated over the oxidative reaction on the Pt surface. It was found that alloying Cu to Pt enhances greatly the catalyst’s activity and robustness. This enhancement is due to the redox reaction of Cuδ+ species into Cu0 with the electrons generated during the reaction. Here, we show that an oxidative pretreatment of the carbon support XC-72R with HNO3 or H2O2 can further boost the catalysis of alcohol oxidation. This is mainly explained by the effect of enriched O-containing functional groups introduced in the support materials, which stabilize the presence of Cuδ+ species in the bimetallic Pt-Cu nanoparticles. This process increases the hydrophilic wettability, which enables more adsorption of reactant molecules and hydroxide ions over the catalyst’s surface, as demonstrated by DFT calculations. The proposed catalytic system is applicable to a variety of substrates, including methanol, ethanol, isopropanol and sorbitol. Our work emphasizes the importance of support’s modification in tuning the interaction within the bimetallic nanoparticles and thus enhancing the electrocatalytic oxidation reactions’ activity.

Comparative study on the properties of wood vinegar prepared from the pretreated Chinese fir: Effect of hydrothermal parameters and hydrogen peroxide

Hydrothermal (HT) pretreatment and hydrothermal oxidative (HO) pretreatment are efficient in upgrading the quality of wood vinegar (WV), while little research pays attention to the systemic comparison between the effects of HT and HO pretreatment on the resulted WV. Therefore, in the present study, the response surface method is adopted first to analyze the effect of HT temperature, solid-to-liquid ratio (S/L), and retention time on the physicochemical properties of WV prepared from Chinese fir (CF). Then, the main compositions (hemicellulose, cellulose, and lignin) of the pretreated CF are quantitatively measured, and the comparative study between the effects of HT pretreatment and HO pretreatment on the yield, density, and compositions of the resulted WV is carried out based on CF composition. The results show that HT temperature is the main parameter that affects the physicochemical properties of the resulted WV. With the increase of HT temperature, the cellulose content of CF samples increases first at 180–230 °C and then decreases at 260–280 °C, the hemicellulose content decreases, and the lignin enriches. The cellulose enrichment gives rise to the increasing WV yield at 180–200 °C and the increasing WV density at 180–230 °C. While the dramatic cellulose decomposition at 230–280 °C results in the decreasing WV yield at 230–280 °C and the decreasing WV density at 260–280 °C. The cellulose is the main component that contributes to the yield and density of WV. Moreover, due to the cellulose enrichment, the contents of the organic compounds, especially the phenols, ketones, and aldehydes, increase dramatically at 180–230 °C, contributing to the lower pH value of the resulted WV. However, HO pretreatment aggravates the decomposition of CF components. During HO pretreatment, the decreases in the hemicellulose content and cellulose content are advanced to 160–200 °C and 180–230 °C respectively, and the lignin content increases. Thus, WV with the comparable yield and density to the unpretreated WV can be prepared at HO pretreatment temperature of 160 °C. Moreover, the pH value of WV decreases significantly after HO pretreatment of 160–200 °C because of the existence of the acid compounds with higher acidity in the resulted WV. Meanwhile, the content of the aldehydes contained in WV prepared from HO pretreated CS increases dramatically.

Non-cyanide Extraction of Gold from Carlin-Type Gold Concentrate by Pressure Oxidation Pretreatment–Jarosite Decomposition–Fine Grinding: An Eco-Friendly Process and Its Mechanism

Non-cyanide Extraction of Gold from Carlin-Type Gold Concentrate by Pressure Oxidation Pretreatment–Jarosite Decomposition–Fine Grinding: An Eco-Friendly Process and Its Mechanism