NH4Cl Concentration Research Articles

Ammonia recovery via direct contact membrane distillation: Modeling and performance optimization

Ammonia recovery from wastewater has positive environmental benefits, avoiding eutrophication and reducing production energy consumption, which is one of the most effective ways to manage nutrients in wastewater. Specifically, ammonia recovery by membrane distillation has been gradually adopted due to its excellent separation properties for volatile substances. However, the global optimization of direct contact membrane distillation (DCMD) operating parameters to maximize ammonia recovery efficiency (ARE) has not been attempted. In this work, three key operating factors affecting ammonia recovery, i.e., feed ammonia concentration, feed pH, and DCMD running time, were identified from eight factors, by a two-level Plackett-Burman Design (PBD). Subsequently, Box-Behnken design (BBD) under the response surface methodology (RSM) was used to model and optimize the significant operating parameters affecting the recovery of ammonia though DCMD identified by PBD and statistically verified by analysis of variance (ANOVA). Results showed that the model had a high coefficient of determination value (R2 = 0.99), and the interaction between NH4Cl concentration and feed pH had a significant effect on ARE. The optimal operating parameters of DCMD as follows: NH4Cl concentration of 0.46 g/L, feed pH of 10.6, DCMD running time of 11.3 h, and the maximum value of ARE was 98.46%. Under the optimized conditions, ARE reached up to 98.72%, which matched the predicted value and verified the validity and reliability of the model for the optimization of ammonia recovery by DCMD process.

Effects affecting ammonia removal in synthetic wastewater by locally isolated Rhodobacter sp strain A1

This research focused on the effects affecting ammonia removal in synthetic wastewater by Rhodobacter sp. strain A1 using one factor at a time method (OFAT). Rhodobacter sp. strain A1 are able to remove ammonia from synthetic wastewater due to its ability to assimilate ammonia. The ammonia removal experiment was conducted under different factors; Rhodobacter sp. strain A1 inoculum size (2%, 4%, 6%), incubation temperature (20°C, 25°C, 30°C, 37°C, 40°C), initial pH of synthetic wastewater (5,6,7,8,9) and initial NH4Cl concentration (5 mg/L, 10 mg/L, 15 mg/L) for four days of incubation period. Then, the solution was tested using Nessler reagent which will produce yellow colour when it reacts with ammonia. The intensity of colour is proportional to the ammonia concentration. This experiment was followed by ammonia quantitative analysis via spectrophotometer at 425 nm. The results obtained were then calculated to get the percentage of ammonia removal by PNSB. The result revealed that the bacterium can achieved 97.90 % efficiency of total ammonia removal at optimum growth condition with 6% of inoculum size, incubation temperature at 30°C and initial pH 7. As a conclusion, this Rhodobacter sp. strain A1 can therefore serve as a good candidate in wastewater treatment for ammonia removal.

Efficient Recovery of Cu from Wasted CPU Sockets by Slurry Electrolysis

In order to maximize the reuse of used electronic component resources, while reducing environmental pollution, Cu metal was recycled from wasted CPU sockets by the reformative slurry electrolysis method. However, the influences on the regulation of the Cu recovery rate and purity from waste CPU slots, by slurry electrolysis, has not been systematically elucidated in previous studies. In this work, the effects of H2SO4 concentration, slurry density, NH4Cl concentration, current density, and reaction time, on the recovery rate and purity of Cu in slurry electrolysis, were researched by systematic experimental methods. The results showed that the recycled metal elements were mainly present as powders from the cathode, rather than in the electrolyte. Moreover, the metallic elements in the cathode powder consisted of mostly Cu and small amounts of Sn and Ni. The recovery rate and purity of Cu were up to 96.19% and 93.72%, respectively, with the optimum conditions being: an H2SO4 concentration of 2 mol/L, slurry density of 30 g/L, NH4Cl concentration of 90 g/L, current density of 80 mA/cm2, and reaction time of 7 h. Compared with previous studies, the Cu recovered in this experiment was present in the cathode powder, which was more convenient for the subsequent processing. Meanwhile, the recovery rate of Cu was effectively improved. This is an important guideline for the subsequent application of slurry electrolysis for Cu recovery.

Nucleation thermodynamics and nucleation kinetics of (NH4)2SO4 under the action of NH4Cl

This study aims to explore nucleation thermodynamics and kinetics of (NH4)2SO4 during cooling under the action of NH4Cl. For this purpose, (NH4)2SO4 was added to the NH4Cl solution in different proportions. The solubility and supersolubility of the mixed solution were measured using a laser method. Then, the (NH4)2SO4 metastable zone width was obtained under different NH4Cl addition and cooling conditions. Studies have shown that the dissolution process of (NH4)2SO4 is an endothermic reaction. Increasing the NH4Cl concentration narrows the (NH4)2SO4 metastable zone width because NH4Cl provides more NH4+ and promotes crystal nucleation, whereas increasing the cooling rate widens the (NH4)2SO4 metastable zone width because the change in the size of the solute molecular clusters in the solution lags behind the transition of the solution state. Additionally, the nucleation kinetics of (NH4)2SO4 under the action of NH4Cl was studied based on the self-consistent Nývlt-like equation and the classical 3D nucleation theory, indicating that the classical 3D nucleation theory can better explain (NH4)2SO4 nucleation kinetics, and the activation energy Esat of the nucleation process obtained by the two models is similar. The study results can provide a reference for the optimization of nucleation of (NH4)2SO4 mother liquor under the condition of high chlorine content.

Desulfurization gypsum carbonation for CO2 sequestration by using recyclable ammonium salt

Based on salt effect and the solubility equilibrium theory of insoluble electrolyte, the technological process of ammonia-enhanced desulfurization gypsum carbonation for CO2 sequestration in NH4Cl-H2O system was studied, and calcium carbonate with different crystal phase and morphology was prepared in this paper. The results showed that the optimal conditions for the dissolution of Ca2+ included NH4Cl concentration of 4 mol/L, LS of 80:1 mL/g, leaching temperature and time of 50 °C and 60 min. The optimal leaching rate was 95.6%, and the leaching residue could be used for cement production. Regarding the optimum conditions of carbonation reaction, the addition amount of ammonia was 10 mL, CO2 flow rate was 80 mL/min, reaction temperature was 40 °C, reaction time was 60 min, and the carbonation conversion rate was 98.54%. The filtrate of carbonation reaction could be recycled for 7 times, and the reaction efficiency was 50.8%. The optimal carbonated product was rhombohedral calcite, and the performance of the product was beyond the requirements of HG/T 2226–2010. The reaction conditions had little influence on the phase and microscopic morphology of the carbonated products. The proposed research is expected to be applied to the CO2 sequestration and the utilization of desulfurization gypsum.

Promotional effect of ammonium chloride functionalization on the performance of polyethersulfone/chitosan composite-based ultrafiltration membrane

This study aims to determine the effect of ammonium chloride (NH4Cl) on the characteristics and performance of polyethersulfone (PES)/Chitosan (CS)-based ultrafiltration composite membranes. The PES membranes were synthesized using phase inversion technique in dimethylacetamide (DMAc) solvent. A mixture of chitosan solution (fixed concentration) and NH4Cl (concentration 100–400 ppm) with ratio 2:1 (v/v) were coated into the PES membrane. The synthesized membranes morphology and properties were characterized by FTIR, SEM, contact angle, mechanical properties, and porosity tests. The membrane performance parameters including water permeability, rejection, and antifouling properties were studied. Incorporation of NH4Cl modified the membrane morphology and improved membrane porosity (49.64–71.5 %). The decrease in the water contact angle (80.21° to 63.53°) has confirmed the improvement of membrane hydrophilicity. Moreover, improved mechanical properties (11–16 MPa) were observed due to NH4Cl addition. The incorporation of NH4Cl improved water flux and specific flux membranes in dead-end cell from 51.34 to 159.18 L/m2∙h and 22–26.53 L/m2∙h∙bar, respectively, and in the cross-flow cell from 82.38 to 182.53 L/m2∙h and from 16.47 to 36.51 L/m2∙h∙bar, respectively. The addition of NH4Cl into membrane remarkably improved the rejection of bovine serum albumine (75.90 %, to 96.79 %), methyl orange (47.18–89.29 %), and methylene blue (60.14–97.34 %) Composite membranes have good fouling resistance as indicated by an increase in the flux recovery ratio (53.58–70.67 %). It is inferred that the addition of NH4Cl improved the performance of PES/chitosan composite membranes in ultrafiltration.

A facile process to optimize performance of regenerated Nd-Fe-B sintered magnets: Chemo-selective dissolution washing

In this work, the recycled Nd-Fe-B powders and regenerated Nd-Fe-B sintered magnets with low impurity content were successfully prepared from Nd-Fe-B magnet sludge via reduction diffusion (RD) method followed by a chemo-selective dissolution washing process. The chemo-selective dissolution effect of various solution (deionized water, dilute acetic acid solution, NH4Cl-methanol solution) was evaluated by impurity content and magnetic properties of the recycled Nd-Fe-B powder. The NH4Cl-methanol solution can selectively remove impurities with minimal damage to the magnetic phase. Besides, the optimal NH4Cl concentration and liquid-to-solid ratio were investigated. As a consequence, the contents of Ca, O, and H after optimal washing process are reduced to 0.07 wt%, 0.31 wt% and 0.22 wt%, respectively. Hence, M3 T is increased to 146.72 emu/g, which is 33% higher than that of the initial sludge. Then, the regenerated Nd-Fe-B sintered magnets with properties of Br = 11.66 kG, Hcj = 16.49 kOe, and (BH)m = 31.78 MGOe were successfully prepared by mixing with 40 wt% Nd4Fe14B alloy powders. Compared with the corresponding regenerated magnets washed with deionized water, the remanence and coercivity are increased by 18% and 59%, respectively.

Screening and fermentation medium optimization of a strain favorable to Rice-fish Coculture.

Rice-fish coculture (RF) is a small ecosystem in which microorganisms are widely distributed in the fish, water environment, soil, and plants. In order to study the positive effects of microorganisms on common carp and rice in the RF ecosystem, a total of 18 strains with growth-promoting ability were screened from common carp (Cyprinus carpio) gut contents, among which three strains had the ability to produce both DDP-IV inhibitors and IAA. The strain with the strongest combined ability, FYN-22, was identified physiologically, biochemically, and by 16S rRNA, and it was initially identified as Bacillus licheniformis. As the number of metabolites secreted by the strain under natural conditions is not sufficient for production, the FYN-22 fermentation medium formulation was optimized by means of one-factor-at-a-time (OFAT) experiments and response surface methodology (RSM). The results showed that, under the conditions of a soluble starch concentration of 10.961 g/l, yeast concentration of 2.366 g/l, NH4Cl concentration of 1.881 g/l, and FeCl3 concentration of 0.850 g/l, the actual measured number of FYN-22 spores in the fermentation broth was 1.913 × 109 CFU/ml, which was 2.575-fold improvement over the pre-optimization value. The optimized fermentation solution was used for the immersion operation of rice seeds, and, after 14 days of incubation in hydroponic boxes, the FYN-22 strain was found to have a highly significant enhancement of 48.31% (p < 0.01) on the above-ground part of rice, and different degrees of effect on root length, fresh weight, and dry weight (16.73, 17.80, and 21.97%, respectively; p < 0.05). This study may provide new insights into the fermentation process of Bacillus licheniformis FYN-22 and its further utilization in RF systems.

A novel electrocoagulation-membrane stripping hybrid system for simultaneous ammonia recovery and contaminant removal

This study developed an innovative and cost-effective electrochemical membrane filtration system, which utilized electrocoagulation (EC) with electrically conductive membranes (ECMs) as cathode and membrane stripping (MS) for simultaneous ammonia recovery and contaminant removal. The novel system takes advantages of the two complementary processes (EC and MS) when sequentially performed. Electrocoagulation produced positively charged coagulants which removed contaminants. ECMs served as cathode of EC in-situ generated OH–, which converted NH4+ ions to volatile NH3. MS recovered NH3 and prevented from membrane fouling or wetting due to the protection of ECMs. The mechanism involves electrocoagulation, electrolysis and electrostatic interaction. Operating conditions (e.g., current density, electrolyte concentration and pollutants concentration) have significant impacts on process performance. Increasing the current density from 0 to 40 A/m2 exerted a positive effect on humic acid (HA) removal, ECM fouling mitigation and ammonia recovery. However, excessive current density (60 A/m2) shortened the contact time between NH4+ and OH–, and thus decreased ammonia recovery. High electrolyte concentration enhanced ammonia recovery, which can be attributed to increased pH and longer contact time between NH4+ and OH–. On the contrary, low electrolyte concentration was beneficial for ECM fouling mitigation through enhancing electrostatic repulsion between membrane electrode and HA contaminants. The improvement of HA concentration not only aggravated ECM fouling, but also had adverse effect on ammonia recovery. NH4Cl concentration had negligible effect on HA removal and membrane fouling, but the generation of OH– became a rate-limiting factor for ammonia recovery at high NH4Cl concentration. Our results demonstrated that the novel system exhibited a competitive performance with other alternatives, with HA removal efficiency of 99.2% and ammonia recovery efficiency of 68.6% at a current density of 40 A/m2, electrolyte concentration of 100 mmol/L, HA concentration of 30 mg/L and NH4Cl concentration of 300 mg/L, which can be considered as an appealing technology for ammonia resource recovery.

Isolation and optimization of a glyphosate-degrading Rhodococcus soli G41 for bioremediation.

A widely used herbicide for controlling weeds, glyphosate, is causing environmental pollution. It is necessary to remove it from environment using a cost-effective and eco-friendly method. The aims of this study were to isolate glyphosate-degrading bacteria and to optimize their degradative conditions required for bioremediation. Sixteen bacterial strains were isolated through enrichment and one strain, Rhodococcus soli G41, demonstrated a high removal rate of glyphosate than other strains. Response surface methodology was employed to optimize distinct environmental factors on glyphosate degradation of G41 strain. The optimal conditions for the maximum glyphosate degradation were found to have the NH4Cl concentration of 0.663% and glyphosate concentration of 0.115%, resulting in a maximum degradation of 42.7% after 7days. Bioremediation analysis showed 47.1% and 40% of glyphosate in unsterile soil and sterile soil was removed by G41 strain after 14days, respectively. The presence of soxB gene in G41 strain indicates that the glyphosate is degraded via the eco-friendly sarcosine pathway. The results indicated that G41 strain has the potential to serve as an in-situ candidate for bioremediation of glyphosate polluted environments.

A novel method for alumina preparation by electrotransformation AlCl3 solution under NH4Cl-catalyzed and CO2-injected conditions

As a refractory industrial solid waste, high-alumina fly ash is discharged into nature in large quantities, causing serious environmental harm. The extraction of valuable components, such as aluminum, from high-alumina fly ash has become a research hotspot at home and abroad. The shortcomings of traditional alumina extraction from high-alumina fly ash include long technological processes, large amounts of waste acid and alkali, and serious equipment corrosion. A novel method for alumina preparation by electrotransformation AlCl3 solution(EAS) under NH4Cl catalysis with injected CO2 has been proposed by Northeastern University. The process has advantages, such as short flow and no waste acid discharge. In this study, the influence of initial NH4Cl concentration in the cathodic chamber on solution pH, phase and morphology of electrotransformation products, phase, D(50) and D(90) of roasting products, and Al recovery rate were examined. Simultaneously, EAS was examined and compared with and without injected CO2, as well as EAS under NH4Cl catalysis with and without injected CO2. The results showed that, when the solution in the cathodic chamber was NH4Cl with CO2 injection, with electrotransformation time extension, pH increased slowly and the morphology of electrotransformation products were all rough and fluffy block structures. Increasing initial NH4Cl concentration effectively improved the product crystallization states, roasting products D(50) and D(90), and Al recovery rate.

Revealing the Enhancement and Degradation Mechanisms Affecting the Performance of Carbonate Precipitation in EICP Process

Given that acid-rich rainfall can cause serious damage to heritage buildings in NW China and subsequently accelerate their aging problem, countermeasures to protect their integrity and also to preserve the continuity of Chinese culture are in pressing need. Enzyme-induced carbonate precipitation (EICP) that modifies the mechanical properties of the soil through enhancing the interparticle bonds by the precipitated crystals and the formation of other carbonate minerals is under a spotlight in recent years. EICP is considered as an alternative to the microbial-induced carbonate precipitation (MICP) because cultivating soil microbes are considered to be challenging in field applications. This study conducts a series of test tube experiments to reproduce the ordinary EICP process, and the produced carbonate precipitation is compared with that of the modified EICP process subjected to the effect of higher MgCl2, NH4Cl, and CaCl2 concentrations, respectively. The modified EICP, subjected to the effect of higher MgCl2 concentrations, performs the best with the highest carbonate precipitation. The enhancement mechanism of carbonate precipitation is well interpreted through elevating the activity of urease enzyme by introducing the magnesium ions. Furthermore, the degradation of carbonate precipitation presents when subjected to the effect of higher NH4Cl concentration. The decreasing activity of urease enzyme and the reverse EICP process play a leading role in degrading the carbonate precipitation. Moreover, when subjected to the effect of higher CaCl2 concentrations, the slower rate of urea hydrolysis and the decreasing activity of urease enzyme are primarily responsible for forming the “hijacking” phenomenon of carbonate precipitation. The findings of this study explore the potential use of the EICP technology for the protection of heritage buildings in NW China.

Evaluation of Biostimulation Efficacy on the Reinforcement of Calcareous Sand

Abstract Calcareous sand is widely distributed on the continental shelf and along the coast and has a low mechanical strength and a high compressibility. The use of biostimulation to activate and enrich ureolytic bacteria induces mineralization to strengthen calcareous sand and has the advantages of being environmentally friendly and less expensive than alternatives. In this study, reinforcement tests and evaluations of calcareous sand columns were carried out to study the effects of different biostimulation schemes on reinforcement. First, six different biostimulation schemes were used to stimulate and enrich ureolytic bacteria in calcareous sand, and the number of bacteria, pH, and urea concentration in the sand columns were biochemically monitored. Then, calcium ions were introduced into the sand columns to induce calcium carbonate precipitation. Finally, the reinforcement effect was evaluated according to the results of mechanical property tests, including mineralization product detection and microbial community change analysis, of the calcareous sand. The results show that (1) the concentrations of yeast extract (YE) and NH4Cl in the biostimulation scheme can significantly affect the stimulation results, in which the best conditions are a YE concentration of 0.2 g/L, an NH4Cl concentration of 100 mM, and an initial pH value of 9.0; and (2) the greater the content and distribution of newly formed calcium carbonate in calcareous sand is, the better the reinforcement effect is. In addition, biostimulation changed the microbial community composition in the calcareous sand, making ureolytic bacteria the new dominant population, which is more conducive to urea decomposition and calcium carbonate formation.

Chlorella vulgaris cultivation in simulated wastewater for the biomass production, nutrients removal and CO2 fixation simultaneously

Chlorella vulgaris (C. vulgaris) was promising microalgae to simultaneously achieve biomass production, carbon dioxide (CO2) fixation, nutrients removal and proteins production especially under different conditions of CO2 gas and wastewaters. Results presented that maximal specific growth rate of C. vulgaris was 0.21–0.35 d−1 and 0.33–0.43 d−1 at 0.038% and 10% CO2 respectively, and corresponding maximal CO2 fixation rate was attended with 4.51–14.26 and 56.26–85.72 mg CO2·L−1·d−1. C. vulgaris showed good wastewater removal efficiency of nitrogen and phosphorus at 10% CO2 with 96.12%–99.61% removal rates. Nitrogen fixation amount achieved 41.86 mg L−1 when the initial NH4Cl concentration was set at 60 mg L−1 at 10% CO2. Improved total protein (25.01–365.49 mg) and amino acids (24.56–196.44 mg) contents of C. vulgaris biomass was observed with the increasing of added CO2 and ammonium concentrations. Moreover, the developed kinetic function of C. vulgaris growth depends on both phosphorus quota and nitrogen quota with correlation coefficient (R2) ranged from 0.68 to 0.97. Computed maximal consumed nutrients concentrations (ΔCmax) based on Logistic function are positively related to initial NH4+-N concentrations, which indicated that adding ammonium could stimulate the utilization of both phosphorus and nitrogen.

High purity metal lead recovery from zinc direct leaching residue via chloride leaching and direct electrolysis

Clean and efficient recovery of lead from zinc direct leaching residue has good environmental and economic benefits. The paper firstly developed a clean and efficient electrolysis process to prepare metal lead from solid lead chloride obtained by leaching zinc direct leaching residue with brine. The solid lead chloride pellets could be well converted into metal lead by direct electrolysis in NH3-NH4Cl electrolyte at constant voltage. Metal lead with 99.1% lead purity was finally obtained by constant voltage electrolysis, and the corresponding extent of lead conversion, current efficiency, and specific energy consumption were 99.32%, 96.75% and 0.575 kW·h/kg respectively. Furthermore, the main technical parameters were also determined, such as a voltage of 2.15 V, working temperature of 45 °C, NH4Cl concentration of 2.0 mol/L, pellet thickness of 1.5 mm and time of 70 min. In addition, the mechanism of the direct electrolysis from solid lead chloride to metal lead in NH3-NH4Cl electrolyte was also proposed, which indicated that the rapid diffusion of electrolyte formed a good conductive network was critical in promoting the direct electrolysis of solid lead chloride. Moreover, the process proposed gives a feasible alternative to recycle lead from zinc direct leaching residue with an environment-friendly method.

Effect of the reactant concentration, bath temperature and deposition time on the properties of CdS thin film prepared by the chemical bath deposition method

CdS thin films for window layers in CdTe solar cells were deposited by the chemical bath deposition method without stirring. The influences of the deposition parameters were studied, such as the reactant concentration, deposition temperature and time on the film properties and solar cell performances, in order to apply in the fabricating of large-area solar cells. Here, we have considered the optical, morphological and structural properties of CdS films with the variation of deposition parameters by using UV–Vis spectroscopy, scanning electron microscopy and X-ray diffraction. Optical measurements revealed that maximum transmittance was obtained for S/Cd ratio of 6. It was found that film grown at 85 °C had better transmittance and showed more compact and smooth surface by means of UV–Vis and SEM measurements. We have demonstrated the transition of cubic and hexagonal crystal phases by the variation of solution PH with NH4Cl concentration through the XRD analysis. The performance of solar cells were estimated by measuring I–V characteristics with different S/Cd ratio, the open circuit voltage and fill factor at different deposition temperature and time. We have determined the optimal parameters such as reactant concentration of CdCl2: 1 mM, (NH2)2CS: 6 mM, NH4Cl: 20 mM, NH3H2O: 1 M, PH: 10.5, bath temperature: 85 °C, deposition time: 1 h.

BIODEGRADATION EFFECTS OF CRUDE OIL-POLLUTED WATER USING BACTERIA ISOLATES FROM SUNFLOWER HUSK ON FISH GROWTH: PARAMETRIC OPTIMIZATION USING TAGUCHI APPROACH

Bacteria isolates from sunflower husk were applied for bioremediation of crude oil-contaminated water.Fish weight was monitored in bioremediated water by gravimetric method. Taguchi design matrix was employed for process parameters optimization, which include reaction temperature (20-60oC), inoculums concentration (20-100 CFU/mL), crude oil concentration (50-250 mL/L), reaction time (1-5 hrs), NH4Cl concentration (20-100 mg/L) and K3PO4 concentration (10-50 mg/L) for crude oil degradation and fish growth. Bacteria isolates were characterized by biochemical tests. Water samples were characterized using gas chromatograph-mass spectroscopy (GC-MS), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and carbon-hydrogen-nitrogen (CHN) analysis. Results revealed optimum crude oil degradation of 96.59 ± 0.03 % for 50 mL/L of crude oil in water supplemented with 100 CFU/mL inoculums, 10 mg/L K3PO4 and 10 mg/L NH4Cl at 60oC reaction temperature and 4 hrs reaction time. Also, optimum fish growth of 93.14 ± 0.04 % was achieved in 50 mL/L of crude oil in solution supplemented with 80 CFU/mL inoculums, 10 mg/L K3PO4 and 20 mg/L NH4Cl at 60oC reaction temperature and 5 hrs reaction time. Conclusively, characterization revealed degradation of hydrocarbons in crude oil-contaminated water from heavy into light fractions by the bacteria isolates.

Removal of Metallic Iron from Reduced Ilmenite by Aeration Leaching

Aeration leaching was used to obtain synthetic rutile from a reduced ilmenite. The reduced ilmenite, obtained from the carbothermic reduction of ilmenite concentrate in a rotary kiln at about 1100 °C, contained 62.88% TiO2 and 28.93% Metallic iron. The particle size was about 200 μm and the size distribution was uniform. The effects of NH4Cl and HCl concentrations, stirring speed, and aeration leaching time on the extent of removal of metallic iron from the reduced ilmenite were studied at room temperature. The results revealed that aeration leaching is feasible at room temperature. When using the NH4Cl system, the metallic iron content was reduced to 1.98% in synthetic rutile, but the TiO2 content only reached 69.16%. Higher NH4Cl concentration did not improve the leaching. Using 2% NH4Cl with 3% HCl, we were able to upgrade the synthetic rutile to 75%, with a metallic iron content as low as 0.14% and a total iron content of about 4%. Synthetic rutile could be upgraded to about 90% using HCl solution alone. HCl and NH4Cl are both effective on the aeration leaching process. However, within the scope of this experiment, hydrochloric acid is more efficient in aeration leaching.

Polyhydroxybutyrate production and increased macromolecule content in Chlamydomonas reinhardtii cultivated with xylose and reduced nitrogen levels

The aim of the current study was to evaluate the production of macromolecules such as polyhydroxybutyrate under pentose supplementation and reduced nitrogen levels in Chlamydomonas reinhardtii. Two batches of experiments were carried out: (1) reduction in the nitrogen (NH4Cl) concentration to 6 and 4 g L−1 and (2) supplementation of 10, 20 and 30 mg L−1 D-xylose together with a reduction in the NH4Cl concentration (6 and 4 g L−1). The addition of 20 mg L−1 D-xylose together with 6 g L−1 NH4Cl resulted in polyhydroxybutyrate production (206.0 mg L−1). The reduction of 8 to 6 g L−1 NH4Cl did not trigger a reduction in the production of either proteins (68.3% w w−1) or carbohydrates (23.3% w w−1) in the cells. The current study demonstrated that nutritional modifications, which until now have been unexplored in C. reinhardtii, triggered the production of macromolecules (polymers, carbohydrates and proteins) with high biotechnological potential.

The growth of Cryptococcus gattii MATα and MATa strains is affected by the chemical composition of their woody debris substrate

Abstract The dominance of MATα among cryptococcal strains has been ascribed to MATa strains being more sensitive to certain environmental factors; however no study has attempted to identify these factors. During the present study we determined whether the chemical composition of woody debris may influence the occurrence of Cryptococcus gattii MATa. We observed a positive correlation between the numbers of C. gattii MATa and the ammonium-nitrogen (NH4–N) concentration in woody debris samples. Subsequent growth studies conducted in woody debris microcosms indicated that this positive correlation is likely not due to additional NH4Cl improving the growth of selected MATa strains. Instead, it might be due to the MATa strains competing better with the MATα strains in the presence of a high NH4Cl concentration compared to a low NH4Cl concentration. This exploratory study paves the way for future studies focused on the interactions of MATa and MATα strains with environmental factors.