Chloride Release Research Articles

Biodegradation of 2- Chlorobenzoic Acid and its other substitutes

Because of the widespread use of these halogenated organic compounds in agriculture and industry, considerable quantities of these compounds' byproducts are discharged into the environment. These chemicals are known as halogenated pesticides. There is one group that, based on the chemical structures of these compounds, is thought to be the most tenacious and poisonous of all the groups. This group is known as the group. A. hydrophila, which was shown to be capable of utilising chlorobenzoate chemicals as a carbon and energy source, was isolated from wastewater treatment plant effluent in Petra, Jordan. Different biodegradation rates (4-chlorobenzoic acid, 5 M/hr; 3,4-dichlorobenzoic acid, 15.5 M/hr; 2-chlorobenzoic acid, 41 M/hr; 3-chlorobenzoic acid, 65 M/hr) were used to achieve these capacities. The release of chloride, the disappearance of the substrate, and finally the development of bacterial cells on these substrates were used to monitor the ability to degrade. Analyses of the ortho or meta ring-cleavage of these aromatic compounds were conducted on A. hydrophila dioxygenases that were physiologically activated by chlorobenzoic acid compounds. The fact that only one 2-dioxygenase activity was found suggests that the ortho route is used for the cleavage. The optimal conditions for 2-CBA chemical breakdown were 3 mM substrate concentration, 25 oC, pH 7, and 200 l inoculum size. Differently from how they affected chloride and cell mass synthesis, the carbon sources had an impact on the breakdown of 2-CBA. Utilized nitrogen sources decreased 2-CBA's ability to degrade and its ability to release chlorine. However, the biodegradation between the 40 and 80 hours was slightly enhanced by the nitrogen source L-proline.

Enhanced triclosan biodegradation by a biphasic bioreactor

Triclosan (TCS), an antiseptic agent that facilitates the formation of microbial resistances, has been widely used and is therefore ubiquitously detectable in wastewater. However, structure and low water solubility limit both microbial transformation kinetic and removal efficiency of TCS. Therefore, the use of solubilizers or non-aqueous phases (NAP) appears to be a suitable approach for rapid, complete, and cost-effective treatment of highly contaminated TCS point sources such as sports clubs, hospitals, industrial wastewater treatment plants or synthesis effluents without dilution effects.The mixed culture TCSmix100 previously isolated and characterized, and able to completely mineralize TCS at stoichiometric chloride release, was investigated in presence or absence of solubilizers in lab-scale well stirred batch reactors. While TCS conversion was limited in solubilizer-free tests due to limited solubility of TCS crystals within the aqueous phase, solubilizers enhanced water solubility, mass transport and microbial kinetics. Thus, TCS transformation rate at initial 1.45 g TCS L−1 was further increased from a high level of 155–172 mg L−1d−1 without solubilizers to 399 mg L−1d−1 or to 888 mg L−1 d-1 providing β-pinene or α-pinene as NAPs, i.e., by a factor of 2.3–5.2, exceeding kinetic parameters of other strains described in literature by at least two orders of magnitude. These results clearly demonstrate the high TCS mineralization capacity of this biphasic treatment technologies and its applicability in treatment of highly contaminated TCS point-sources to eliminate recalcitrant contaminants at high levels before getting diluted.

Production and characterization of lightweight aggregates from municipal solid waste incineration fly-ash through single- and double-step pelletization process

The performance of a cold-bonding pelletization process was investigated for lightweight aggregates (LWAs) production from municipal solid waste incineration (MSWI) fly-ash (FA), by including multiple waste materials in the aggregate mixture. Before pelletization, FA was pre-treated by washing with water, which led to a reduction of chloride (66.79%) and sulphate (25.30%) content. This was further confirmed by XRF and XRD analyses, which showed a reduction of chloride elements and the content of chlorine crystalline phases. The pelletization process was carried out using both single- and double-step methods. For single-step pelletization, all the mixtures contained 80% FA, combined with various compositions of cement (5, 10, and 15%) and granulated blast furnace slag (GBFS) (5, 10, and 15%). For the double-step pelletization 30% of cement and 70% of marble sludge (MS) were added to each of the previous mixtures. The apparent density of all the aggregates varied between 1.60 and 1.87 g cm−3, suggesting their suitability to be classified as LWAs. Aggregates produced from double-step pelletization showed improved characteristics, with water absorption capacity and open porosity generally lower compared to the corresponding aggregates from the single-step pelletization. The best values of compressive (crushing) strength (almost 11 MPa) were observed for double-step pelletization aggregates with initial cement: GBFS mixture of 15%:5%. Results from leaching tests showed an overall significant release of chloride and sulphate. Nevertheless, leaching from double-step pelletization aggregates was reduced by 1.73-4.02 times for chloride and 1.58-5.67 times for sulphate, further suggesting that better performances are achievable through the addition of an aggregate second layer.

Freshwater-Derived Streptomyces: Prospective Polyvinyl Chloride (PVC) Biodegraders.

Polyvinyl chloride (PVC) is widely used in industrial applications, such as construction and clothing, owing to its chemical, physical, and environmental resistance. Owing to the previous characteristics, PVC is the third most consumed plastic worldwide and, consequently, an increasing waste accumulation-related problem. The current study evaluated an in-house collection of 61 Actinobacteria strains for PVC resin biodegradation. Weight loss percentage was measured after the completion of incubation. Thermo-gravimetric analysis was subsequently performed using the PVC incubated with the three strains exhibiting the highest weight loss. GC-MS and ionic exchange chromatography analyses were also performed using the culture media supernatant of these three strains. After incubation, 14 strains had a PVC weight loss percentage higher than 50% in ISP-2 broth. These 14 strains were identified as Streptomyces strains. Strains 208, 250, and 290 showed the highest weight loss percentages (57.6-61.5% range). The thermal stability of PVC after bacterial exposure using these three strains was evaluated, and a modification of the representative degradation stages of nonincubated PVC was observed. Additionally, GC-MS analysis revealed the presence of aromatic compounds in the inoculated culture media, and ionic exchange chromatography showed chloride release in the supernatant. A mathematical relation between culture conditions and PVC weight loss was also found for strains 208 and 290, showing an accuracy up to 97.99%. These results highlight the potential of the freshwater-derived Streptomyces strains as candidates for the PVC biodegradation strategy and constitute the first approach to a waste management control scale-up process.

Drug release and thermal properties of magnetic cobalt ferrite (CoFe2O4) nanocomposite hydrogels based on poly(acrylic acid-g-N-isopropyl acrylamide) grafted onto gum ghatti

The aim of this study was to better understand the underlying drug release characteristics from Gg-cl-poly(NIPA-co-AA)/CoFe2O4 hydrogel containing metformin hydrochloride as model drug. Nanocomposite's hydrogel of gum ghatti free radical polymerization is used for the controlled release of metformin hydrogen chloride. Gum ghatti and CoFe2O4 nanoparticle dispersion were grafted by acrylic acid and N-isopropylacrylamide, employing graft copolymerization in the presence of N, N′–methylene-bis-acrylamide (MBA) as cross linker, and ammonium persulfate (APS) as initiator. The synthesized nanocomposites hydrogel was characterized using FTIR, SEM, TGA and DSC. Drugs were all released through diffusion in the hydrated matrix and polymer relaxation, irrespective of the drug solubility. In vitro drug release studies, at different pH values of pH = 4.0, 7.4 and 9.2 was employed. Drug release was influenced by the change of pH. The pH of 7.4 was considered as the optimized pH for maximum drug release. The nanocomposites hydrogel was loaded with metformin hydrochloride drug (100 mg) which is an antidiabetic drug to investigate the release profiles in PBS (pH 7.4). The effects of polymer level and initial drug loading on release depended on drug properties. Different models were studied for release kinetic studies which showed that the zero-order model suggested the best kinetics release studies in PBS (pH- 7.4) and showed sustained release. The kinetics of drug release were discovered to fit the Korsmeyer-Peppas model with n > 1, indicating a specific case II transport mechanism.

(Invited) Surface Electrochemistry and Physicochemical Behaviors of Carbon and Compound Electrodes in Electrochemical Separation Systems

In recent years, electrochemical separation systems have received a great attention due to their excellent capabilities in environmental remediation, water desalination, and resource recovery. The performances of electrochemical separation systems are often interpreted in terms of capacity and selectivity, both of which are highly dependent on electrode materials. For instance, capacitive deionization (CDI) used for desalination of water employs activated carbon electrodes, as it enables capture and release of sodium chloride in large amounts. In addition, lithium-ion selective electrode such as delithiated LiMn2O4 (i.e. λ-MnO2) or LiFePO4 plays an essential role in selectivity of electrochemical lithium recovery systems. However, although the importance electrode materials cannot be overemphasized for such electrochemical separations, it is also true that we are yet to achieve a sufficient level of understanding on their behaviors in the systems, which is necessary to establish rational electrode-design strategies to enhance capacity and selectivity of the electrochemical separation systems. In this talk, our recent findings on surface electrochemistry of carbon electrodes in electrochemical desalination will be introduced, together with an overview on the non-favorable Faradaic reactions thoroughly characterized with the assistance of various X-ray and electrochemical techniques. Additionally, development of heteroatom-doped carbon material and how it resulted in a highly stable CDI performance will be presented. Moreover, I will talk about our efforts on characterization of physicochemical behavior of λ-MnO2 in electrochemical lithium recovery systems, based on which a significantly higher utilization rate of the electrode materials could be achieved.

A new co-processing mode of organic anaerobic fermentation liquid and municipal solid waste incineration fly ash

A new co-processing mode of waste liquid from anaerobic fermentation of organic wastes and municipal solid waste incineration fly ash (MSWI-FA) dechlorination is reported in this paper. Taking acetic acid, the most common organic acid in anaerobic fermentation systems, as the representative of anaerobic fermentation organic acids, the improvement of the dechlorination effect and the mechanism of washing MSWI-FA with low concentrations of organic acid lotion were explored. The chlorine content of MSWI-FA was reduced to 0.82% after the optimal process washing pretreatment. Three anaerobic fermentation waste liquids (AFWLs) were used to verify that the chlorine content of MSWI-FA could be reduced to less than 1%, and the dechlorination effect of brewery wastewater, which reduced the chlorine content of MSWI-FA to 0.91%, was the best at this. The influence of the washing process on MSWI-FA pyrolysis was reflected in the whole process. The release of chloride decreased and the weight loss was mainly due to the release of CO2. The melting point of MSWI-FA, washed by the optimal process, was reduced by nearly 30 ℃, and only 0.06% chlorine remained after calcination at 1100 ℃, which was extremely beneficial in reducing the release of trace elements in MSWI-FA during heat treatment, and for the preparation of cement raw meal.

Catalytic Chemo-, Regio-, Diastereo-, and Enantioselective Bromochlorination of Unsaturated Systems Enabled by Lewis Base-Controlled Chloride Release.

A new strategy is described for the Lewis base-catalyzed bromochlorination of unsaturated systems that is mechanistically distinct from prior methodologies. The novelty of this method hinges on the utilization of thionyl chloride as a latent chloride source in combination with as little as 1 mol % of triphenylphosphine or triphenylphosphine oxide as Lewis basic activators. This metal-free, catalytic chemo-, regio-, and diastereoselective bromochlorination of alkenes and alkynes exhibits excellent site selectivity in polyunsaturated systems and provides access to a wide variety of vicinal bromochlorides with up to >20:1 regio- and diastereoselectivity. The precision installation of Br, Cl, and I in various combinations is also demonstrated by simply varying the commercial halogenating reagents employed. Notably, when a chiral Lewis base promoter is employed, an enantioselective bromochlorination of chalcones is possible with up to a 92:8 enantiomeric ratio when utilizing only 1-3 mol % of (DHQD)2PHAL.

The role of Carica papaya latex bio-catalyst in recycling of used fibre pulp

Biotechnology-based enzymes are challenging in reducing production costs and presenting environmentally friendly technologies. The study deal with an experimental investigation of the bio-catalyst made of Carica-papaya latex in recycling used fibre pulp in industry. The experiments used a test specimen from 5 g of dry pulp mixed with 150 mL of water and a mixture composition of 3.23%. Other similar experiments applied a bio-catalyst from papaya latex by dipping 6 g of unripe papaya into the water. A heating process of the test material was performed at a temperature of 50 °C to optimise the work of enzymes in the pulping process, and then Carica papaya fruit was removed from the container after 3 min. In addition, the characterisation of test materials in the hand-sheets form was realised in dry conditions. The tests carried out include Scanning electron microscope (SEM), Energy-dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared (FTIR) Spectroscopy, acidity (pH), turbidity, whiteness, and freeness. The results indicated that the addition of bio-activator in water produces bio-ions (positive and negative), which play a vital role in eroding pulp functional groups, influencing the construction of stalagmite micro valleys, and changing the surface morphology of pulp. The release of Bromide, Iodide, Chloride and Fluoride functional groups causes brightening effects and increases the degree of whiteness, impacting the pre-whitening process. Meanwhile, changes in the stalagmite micro valley and the surface morphology of the pulp cause a bulky effect and ultimately reduce the degree of freeness.

The potential for bacteria from carbon-limited deep terrestrial environments to participate in chlorine cycling.

Bacteria capable of dehalogenation via reductive or hydrolytic pathways are ubiquitous. Little is known, however, about the prevalence of bacterial dechlorination in deep terrestrial environments with a limited carbon supply. In this study we analyzed published genomes from three deep terrestrial subsurface sites: a deep aquifer in Western Siberia, the Sanford Underground Research Facility in South Dakota, USA, and the Soudan Underground Iron Mine (SUIM) in Minnesota, USA to determine if there was evidence to suggest that microbial dehalogenation was possible in these environments. Diverse dehalogenase genes were present in all analyzed metagenomes, with reductive dehalogenase and haloalkane dehalogenase genes the most common. Taxonomic analysis of both hydrolytic and reductive dehalogenase genes was performed to explore their affiliation; this analysis indicated that at the SUIM site, hydrolytic dehalogenase genes were taxonomically affiliated with Marinobacter species. Because of this affiliation, experiments were also performed with Marinobacter subterrani strain JG233 ('JG233'), an organism containing three predicted hydrolytic dehalogenase genes and isolated from the SUIM site, to determine whether hydrolytic dehalogenation was an active process and involved in growth on a chlorocarboxylic acid. Presence of these genes in genome appears to be functional, as JG233 was capable of chloroacetate dechlorination with simultaneous chloride release. Stable isotope experiments combined with confocal Raman microspectroscopy demonstrated that JG233 incorporated carbon from 13C-chloroacetate into its biomass. These experiments suggest that organisms present in these extreme and often low-carbon environments are capable of reductive and hydrolytic dechlorination and, based on laboratory experiments, may use this capability as a competitive advantage by utilizing chlorinated organic compounds for growth, either directly or after dechlorination.

Controlled release, antimicrobial activity, and oral mucosa irritation of cetylpyridinium chloride-montmorillonite incorporated in a tissue conditioner.

This study examined the controlled release of cetylpyridinium chloride (CPC) from a tissue conditioner (TC) containing CPC-montmorillonite (CPC-Mont), the associated antimicrobial activity, and oral mucosa irritation. The CPC release test was performed daily for 28 days in three test solutions: distilled water, 0.2 M NaCl, and 0.2 M HCl. The antimicrobial activities for 7, 14, 21, and 28 days against Candida albicans, Staphylococcus aureus, and Streptococcus mutans were assessed according to the JIS Z 2801/ISO 22196 standard. An oral mucosa irritation test was conducted using cheek pouches in five male hamsters according to the ISO 10993-10:2010 standard. The amount of CPC released each day and the cumulative amount released over 28 days (6.12 mg) were less than the daily safe maximum of sore throat medicines (8 mg). Additionally, TC with CPC-Mont could sustain antimicrobial activity against adherent bacteria for 14 days and has no oral mucosa irritation potential.

Kinetics study of ultrasound-assisted chloride release from cementitious materials

This paper studied the influence of ultrasound on chloride release from cementitious materials. Results showed that ultrasound power enhanced both equilibrium point and chloride release rate, while ultrasound frequency mainly promoted the release rate. Kinetics analysis demonstrated that chloride release was controlled by the chemical reaction step. Its dominant role was not weakened by ultrasound. A decrease of physically and chemically bound chlorides was found after ultrasound irradiation. Interestingly, the physically bound chlorides decomposed faster than the chemically bound ones. Overall findings clearly demonstrated that ultrasonic waves had a beneficial effect on improving the chloride release from cementitious materials.

Triclosan biodegradation performance of adapted mixed cultures in batch and continuous operating systems at high-concentration levels

Pollutants like triclosan (TCS) of medium to high logKow value tend to be mainly adsorbed and poorly biodegraded during waste water treatment, complicating removal after release. Complete mineralization of TCS is crucial, since transformation products may be even more toxic, but has been proven only in a few cases. In this study, the performance of different batch (cultivation flask, TCSmix100) and continuous operating systems (submerged biotrickling filter, TCSmix100; biomembrane reactor, TCSmix200) was tested with two pre-adapted mixed cultures named TCSmix100 and TCSmix200, and compared to non-adapted cultures in a biotrickling filter and a sand filter as reference systems. Mineralization rates up to 172 mg TCS/L/d were observed during batch conditions for TCSmix100 at 1.45 g TCS/L as initial concentration. Triclosan was completely mineralized by both cultures, as shown by stoichiometric release of chloride at conversion rates of 5,7–11.4 mg TCS/L/d (biotrickling filter) and 0.72–1.45 mg TCS/L/d (biomembrane reactor) at 20 and 7.5–15 mg TCS/L as influent concentrations. In TCSmix100, Achromobacter sp. was identified as the relevant strain in TCS biodegradation. Community analysis of TCSmix200 revealed Nitrosomonas europaea, Nitrospira moscoviensis, Nitrosospira multiformis , and Rhodanobacter lindaniclasticus as the predominant strains. In contrast, chloride formation and triclosan elimination in the non-adapted biotrickling filter was less than 12% of the expected chloride concentration at hydraulic retention times up to 60 d. In the reference sand filter, TCS abatement was 42.8% in average with neither formation of chloride nor increase in biofilm density, indicating mostly sorptive or precipitative effects for elimination. With mineralization levels surpassing those of comparable references by a factor of 3–11, both adapted fixed-biomass reactor systems proved highly suitable for treatment of effluents containing high concentrations of TCS as they occur in industrial discharges or concentrates of membrane-based wastewater treatment plants. • Two aerobic mixed cultures were enriched able to completely mineralize triclosan (TCS) • Mixed cultures were dominated by Achromobacter sp. or nitrifying bacteria • Turnover rates were up to two orders higher than in literature (172 mg TCS L −1 d −1 ) • Fixed biomass systems showed stable performance during 110 d and 137 d of operation • TCS was solely eliminated by sorptive effects in a sand filter as reference system

Theoretical Study on the Mechanism of the Initial Ammonolysis Reactions of the Main Raw Materials for the Formation of SiBCN Ceramics

AbstractA detailed mechanism investigation of the formation of B−N, Si−N and C−N bonds is conducive to the design and synthesis of siliconboroncarbonitride (SiBCN) ceramics to meet application requirements under extreme conditions. Boron trichloride (BCl3), methyldichlorosilane (MDCS) and methylvinyldichlorosilane (MVCS) are the most commonly used raw materials, and they can react with amino compounds, such as ammonia (NH3), methyl ammonium (CH3NH2), and hexamethyldisilazane (HMDZ, (CH3)6Si2NH) in the synthesis of SiBCN precursors. In this paper, quantum chemical calculations were used to study the ammonolysis mechanism of three raw materials with three amino compounds at the M06‐2X/6‐311G(d,p) level of theory. The structural properties, reaction pathways, energy barriers, reaction rates, and other aspects were discussed in detail. The results show that compounds containing B−N, Si−N and C−N bonds can be formed through a synergistic reaction mechanism with the release of ammonium chloride or trimethylchlorosilane (TMCS). The ammonolysis processes of BCl3 have absolute advantages in both kinetics and thermodynamics. The reaction of MDCS has the lowest energy barrier. All ammonolysis reactions are thermodynamically exothermic processes. The calculated results agree well with the experimental observations and provide an explanation for the initiation process of precursor synthesis.

Investigation of chloride release characteristic of Chlorine-Based Anti-Icing asphalt mixture

Anti-icing asphalt pavement is an effective way to alleviate snow and ice disasters in winter roads, and the release characteristics of active ingredients determine the snow melting effect of the asphalt pavement. By using the ion-selective electrode (ISE) method, the cumulative release concentration and single release concentration were used as indicators to analyze the macro release characteristics of the snowmelt active ingredients, chloride ions. The release of chloride goes through the rapid release stage, stable release stage, and release stop period. The effects of asphalt mixture type, asphalt type, and temperature on the macro release characteristics were also discussed. In order to explain the release characteristic of active ingredients at a molecular level, a simulation system of asphalt and finite components were developed with the help of molecular dynamics research methods. The absorption and diffusion characteristics of active ingredient and asphalt at the molecular scale were explored in combination with variations in binding energy, radial distribution function, and chloride diffusion coefficient. The effects of temperature, pressure, and the agent proportion on the micro-release characteristics of active ingredients were clarified.

Poly(allylamine)/tripolyphosphate coacervates for encapsulation and long-term release of cetylpyridinium chloride

Complex coacervates formed through the association of poly(allylamine hydrochloride) (PAH) with pentavalent tripolyphosphate ions (TPP) have low solute permeabilities and enable multi-month release of small, water-soluble molecules. To this end, we have recently shown PAH/TPP coacervates to be highly effective in encapsulating and slowly releasing bioactive anionic surfactants. Here, we extend this work to the encapsulation and release of cationic surfactants and exploring the effects of the PAH/TPP/surfactant mixing order. Using cetylpyridinium chloride (CPC) as a model cationic amphiphile, we show that (like their anionic counterparts) cationic surfactants can be encapsulated in PAH/TPP coacervates in high concentrations (exceeding 20% of the coacervate weight). The high loadings evidently reflect the CPC/TPP association (which concentrates the CPC within the forming coacervates) and are maximized at high CPC concentrations, low PAH/TPP concentrations, and when the CPC is initially mixed with the TPP. This CPC encapsulation significantly affects the PAH/TPP coacervate properties (likely due to the considerable CPC/TPP association strength) and makes the coacervates opaquer and higher swelling, but less adhesive and less susceptible to spreading from their application sites. Besides increasing with their CPC content, the coacervate swelling varies with the PAH/TPP/CPC mixing order and is greatest when the CPC and TPP are mixed first. Once loaded, the CPC can be released over multiple months, with some control over the release rates (which, initially, are on the order of 10 µg/d, but tend to gradually fall below ~1 µg/d within the first 1 – 4 weeks). These findings suggest that PAH/TPP coacervates may be suitable for the low-dosage sustained release of cationic surfactants in applications where the release media has a low volume and is not frequently exchanged. More broadly, this work also indicates that: (1) effective encapsulation of active small molecules within polyelectrolyte/small multivalent counterion coacervates does not (when the payload associates with the small multivalent ions) require payload/polymer affinity; and (2) nonequilibrium effects during the formation of these payload-bearing coacervates can have long-term consequences on their properties and performance.

The Resistance of Novel Concrete Prepared by Gap-Graded Blended Cement under Chloride-Sulfate Attack

The resistance of concrete under chloride-sulfate attack dominates the durability of marine constructions. The binder played a more important role in chloride-sulfate resistance of concrete due to the dynamic hydration process. Incorporating supplementary cementitious materials (SCMs) was beneficial to the microstructure densification of cement paste, but the low hydraulic activities of SCMs resulted in the decrease of mechanical properties, activating activities of SCMs would raise the cracking risk of cement paste. On the basic of close packing theory, a gap-graded blended cement contained calcined hydrotalcite and metakaolin was adopted to prepare concrete with high resistance under chloride-sulfate attack in present study. The gap-graded blended cement concrete presented comparable strength with Portland cement concrete, even though only 25% clinker used in the blended cement. Because of the continuous hydration of alumina-rich SCMs and functional components, the secondary hydration products with high chloride binding capacity helped blocking ions ingress, resulting in the one-magnitude decrease of chloride diffusivity. At the early period of soaking duration in chloride-sulfate solution, the sulfate ions were beneficial to delaying the migration of chloride. And the cracks introduced by expansive products from sulfate attack would observably accelerate the release and continuous ingress of chloride at late period.

Release characteristics of chloride during single droplet drying process of desulfurization wastewater

AbstractBACKGROUNDThe release characteristics of chloride during the evaporation process of desulfurization wastewater droplets were studied by single droplet drying experiments. The mass, size and temperature variation of droplets during the evaporation process were measured and the release mechanism of chloride was revealed. In addition, the influence of temperature, pH value and metal cation species on the release characteristics of chloride was explored.RESULTSCombined with the evaporation process, chloride release could be divided into three stages: free water evaporation, shell instability and crystallization chloride salt hydrolysis. In the initial stage, moisture removal was the dominant phenomenon and almost no chloride release was observed. During the stage of shell instability, cycles of droplet inflation and rupture took place, and the release amount of chloride accounted for 51.2% of the total release amount in the typical working conditions. Hydrolysis of crystallization chloride salt played a key role in chloride release and about 46.0% chloride release could be traced during the last stage. High temperature would boost the chloride release; with pH value increasing from 3 to 9, chloride release decreased from 39.7% to 28.8%; a higher magnesium concentration would enhance the chloride release due to the greater hydrolysis strength.CONCLUSIONChloride in the wastewater droplet would not transfer to the gas phase until the evaporation proceeded to the stage of shell instability. The chloride release characteristics investigated in this work are expected to control the HCl emission in practical engineering of hot flue gas evaporation. © 2021 Society of Chemical Industry (SCI).

Biomass ash formulations as sustainable improvers for mining soil health recovery: Linking soil properties and ecotoxicity

There is a growing need to recover degraded soils to restore their essential ecosystem services and limit damages of anthropic activities onto these systems. Safe and sustainable solutions for long-term recovery must be designed, ideally by recycling existing resources. Using ash from combustion of residual forest biomass at the pulp and paper industry is an interesting and sustainable strategy to recover mining soils. However, formulations must be found to limit the potential toxicity associated with soluble salts and chloride that ash contains. Here, we assessed the effectiveness of three field ash-based amendments for the recovery of three highly acidic soils from Portuguese abandoned mines. Three amendments were tested: an un-stabilized mixture of ash and biological sludge, granulated ash, and granulated ash mixed with composted sludge. One year after application in open field plots (in the scope of LIFE No_Waste project), soil health restoration was evaluated through (i) soil physico-chemical characterization and (ii) soil habitat functions though standardized ecotoxicological tests.This study highlights that stabilized materials provided nutrients, organic matter and alkalinity that corrected soil pH and decreased metal bioavailability, while controlling the release of soluble salts and chloride from ash. This soil improvement correlated with improved soil model organisms’ reproduction and survival. For similar amendment, the native soil properties studied (as soil native electrical conductivity) affected the level of organism response.This work provides evidence that ash stabilization, formulation and supplementation with organic matter could be sustainable strategies to restore highly degraded mining soils and to recover their ecological functions. It further highlights the importance of analyzing combined effects on soil physico-chemical properties and ecological function recovery to assess restoration strategy efficiencies in complex multi-stressor environments.

Chloride release characteristics of desulfurization wastewater droplet during evaporation process using the single droplet drying method

The desulfurization wastewater evaporation technology is an effective way to realize zero-liquid discharge (ZLD). However, the release of chloride during the evaporation process is still a great challenge, which may cause severe chloride enrichment in the wastewater. In this work, the single droplet drying (SDD) method was utilized to investigate the chloride release characteristics during the evaporation process. The three periods of chloride release were first proposed based on the chloride release ratio and wastewater droplet's features (mass, temperature, and diameter). With the removal of the free moisture, the first period (Free water evaporation) was initiated, and almost no released chloride was detected; In the unstable shell period, 19.8% chloride would release there, mainly due to the increased droplet's temperature; Approximately 10% chloride would release during the shell pyrolysis period, which was directly related to the hydrolysis of the chloride-based salt hydrates in the evaporation particle. Besides, the chloride release characteristics at different cations species and ambient temperature were investigated. The desulfurization wastewater with a higher Mg2+ concentration would be more likely to release chloride during the evaporation process. With the temperature increased from 150 to 300℃, the chloride release ratio would improve from 14.56 to 29.8% due to the disruption of the shell and the hydrolysis degree at a higher temperature. In practical engineering practices, a balance point between chloride release and evaporation efficiency should be found, and the Mg2+ in the wastewater should be pre-treated before entering into the evaporation system.