Effects Of Different Organic Acids Research Articles

Comparison of lactic and propionic acid hydrolysis for production of xylo-oligosaccharides and ethanol from polysaccharides in Toona sinensis branch

Xylan-type hemicellulose hydrolysis by an organic acid solution for the production of xylo-oligosaccharides (XOS) is efficient and eco-friendly, but the effects of different organic acids on XOS production from Toona sinensis branch (TB) biomass is limited. In this work, under the conditions of 170 °C for 60 min, 33.1 % and 38.7 % XOS yields were obtained from polysaccharides present in TB by 2 % lactic acid (LA) and 6 % propionic acid (PA), respectively. Then 77 % of the lignin was removed by hydrogen peroxide−acetic acid pretreatment system, and 39.5 % and 44.7 % XOS yield were obtained from polysaccharides in delignification TB by 2 % LA and 6 % PA, respectively. It was found that PA hydrolysis, especially from delignified TB, resulted in higher XOS yield and purity compared to LA hydrolysis. Moreover, the content of byproducts (xylose, hydroxymethyl-furfural and furfural) in PA hydrolysate was lower. Following the hydrolysis process, the simultaneous saccharification and fermentation of the TB solid residue achieved an ethanol yield of 71.5 %. This work proposed an integrated process to preferentially convert the TB hemicellulose into valuable XOS and then convert the cellulose into ethanol. This process had the advantages of eliminating the need for isolation and purification of xylan, and the potential to obtain multiple products from the same raw material.

Physiological mechanisms of exogenous organic acids to alleviate aluminum toxicity in seedlings of mungbean, buckwheat, and rice

One of the major constraints for crop yield in acidic soils is the phytotoxicity of aluminum ions (Al3+), which primarily affects the roots. To mitigate the harmful effects of Al toxicity, plants use organic acids to chelate Al internally and externally. In this study, the effects of exogenous organic acids on Al toxicity in rice, mung bean, and buckwheat were investigated. Specifically, the study examined the ameliorative effect of three organic acids (oxalic acid, malic acid, and citric acid, each at a concentration of (100 μmol/L) on root elongation, fresh weight, Al content, organic acid key enzymes, and rhizosphere pH in hydroponic media containing (100 μmol/L) Al. The experimental results revealed species-specific responses to aluminum tolerance and the alleviating effects of different organic acids. Buckwheat was found to be the most aluminum-tolerant, followed by mung bean, while rice was the least tolerant. Exogenous application of oxalic acid promoted root elongation, increased root fresh weight, and enhanced the activity of the PEPC enzyme in mung bean. Malic acid, on the other hand, alleviated Al toxicity in rice by promoting root elongation, increasing root fresh weight, enhancing the activity of the PEPC enzyme, and decreasing the activity of the MDH enzyme. In buckwheat, citric acid application reduced Al toxicity by promoting root elongation, increasing root weight, and decreasing the activities of CS and GO enzymes. These findings indicate that different organic acids can reduce Al toxicity in different plant species by employing different physiological mechanisms.

The Effect of Different Organic Acids and Their Combination on the Cell Barrier and Biofilm of Escherichia coli.

Organic acids are natural antimicrobial compounds commonly used in the food industry. In this study, acetic, lactic, butyric, citric, and malic acid at minimum inhibitory concentrations and their combinations at optimal inhibition concentrations were used to treat E. coli, and the effects on the cell barrier and biofilm of E. coli were evaluated. Acetic acid showed the highest membrane-damaging effect, while citric acid and malic acid could specifically damage the cell wall of E. coli, leading to alkaline phosphatase leakage. The RT-qPCR results showed that organic acids upregulated the membrane-protein-related genes of E. coli, and the combination of organic acids had a wider range of effects than single organic acid treatment. Moreover, organic acids inhibited the formation of E. coli biofilm and cellular activity within the biofilm. This study showed that the combination of organic acids plays a synergistic inhibitory role mainly through multiple destructive effects on the cell barrier and exhibited synergistic anti-biofilm effects. The three-three combination of acetic, lactic acid, and a third organic acid (butyric, citric, or malic) can play a better synergistic antibacterial effect than the two-pair combination of acetic and lactic acid. These findings have implications for the usage, development, and optimization of organic acid combinations.

Study on the bactericidal effect of different organic acids on Escherichia coli and its application in slaughterhouse

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Organic acid-compatibilized potato starch/guar gum blend films

Global plastic pollution has increased alarmingly necessitating urgent solutions, like the development of biodegradable films. Therefore, the present study was taken up to develop and examine the effect of different organic acids on physical, barrier, mechanical, and structural properties of potato starch-guar gum based biodegradable composite film. Potato starch-guar gum films were modified by incorporating succinic, malic and tartaric acids at four different concentrations (4, 8, 12 &16%). The results of FTIR spectra showed a band at around 1724 cm−1 for all the acids incorporated films which is attributed to the formation of ester groups in the developed films. Crystallinity of all the films diminished after incorporating the organic acids into potato starch-guar gum film. It was observed that except succinic acid, other two acids contained films enhanced water vapor permeability by around 30% compared to the native potato starch-guar gum film (1.9 × 10−7 g mm/m2/Pa/s) due to higher dissociation constant the acids. Tensile strength of all the films decreased to around 2 MPa compared to native potato starch-guar gum films (8.3 MPa), whereas percentage elongation at break increased from 8.6% to 33%. Solubility in buffer solutions, opacity and morphology of the films were also investigated.

Effect of organic acids fed through drinking water on carcass and internal organs of broiler chickens

A Six week study was carried out to investigate effect of different organic acids (OAs) fed through drinking water on carcass yield and internal organs weight of broiler chickens. The OAs were acetic acid (AA) butyric acid (BA), citric acid (CA) and formic acid (FA). One hundred and fifty (150) day old AborAcre-plus chicks were used. There were five treatments. Treatment 1 which served as control (CON) consumed water with no organic acid, while treatments 2,3, 4 and5 respectively were offered drinking water treated with 0.25% acetic acid (AA), butyric acid (BA), citric acid (CA) and formic acid (FA). Each treatment was replicated three times each having 10 birds arranged in completely randomized design (CRD). Feed and water were offered ad libitum. Results showed that dressed carcass weight and breast weight were improved by all the organic acids. While only AA positively influenced the thigh weight, all the OAs drinking water fed resulted to smaller drumstick compared to the CON. Feeding of AA, BA and FA through drinking water increased (PSO.05) deposition of abdominal fat. Weight of pancreas, small intestine, caecum and large intestine was significantly (P<0.05) higher in CON. The gall bladder was significantly (P<0.05) bigger in all the OA groups. Conclusively, OAs could be fed through the drinking water for improved percentage carcass yield, breast meat and larger gall bladder and invariably bile volume

Carcass yield and internal organs of broiler chickens fed diets treated with organic acids

An experiment was conducted to determine the effect of different organic acids (OAs on carcass yield and internal organ characteristics of broiler chickens. The OAs were acetic acid (AA) butyric acid (BA), citric acid (CA) and formic acid (FA). One hundred and fifty (150) day old AborAcre - plus chicks were used. There were five dietary treatments. Diet 1 which served as control (CON) contained no OA, while diets 2, 3, 4 and 5 respectively contained 0.25% AA, BA, CA and FA which replaced palm kernel cake in which each treatment was replicated three times with 10 birds per replicate and arranged in completely randomized design (CRD). Diets were both isoenergetic and isonitrogenous. The experiment lasted for 8 weeks. Feed and water were given ad libitum. At the end of the 8 weeks of feeding, 3 birds from each replicate giving a total of 9 birds per treatment were slaughtered for carcass and internal organ evaluation. Result from the carcass evaluation showed that there were no significant differences (P>0.05) in dressed carcass weight, thigh, wing and drumstick. All the OAs except BA produced bigger breast meat compared to the birds fed control diet. The weight of the backcut was significantly (P<0.05) reduced by FA compared to the birds on control diet. Birds that consumed FA treated diet deposited more abdominal fat and AA produced the least (P<0.05). Internal organ result indicated that both the liver and the kidney were not negatively affected by OA treated diets. Caecum and the large intestine were significantly larger in than those obtained from birds fed the control diet. Therefore, addition of the OAs except BA to broiler diets could be a good practice considering their positive effect on the breast meat which is a premium cut part. 

Effect of finisher diets treated with organic acids on carcass and internal organs of broiler chickens

An experiment was carried out to determine the effect of different organic acids (OAs) on carcass yield and internal organ characteristics of broiler chickens. The OAs were ethanoic acid (acetic acid - AA), butanoic acid (butyric acid - BA), citric acid (CA) and methanoic acid (formic acid - FA). One hundred and fifty (150) day old AborAcre-plus chicks were used. There were five dietary treatments. Diet 1 which served as control (CON) contained no OAs, while 0.25% of AA, BA, CA and FA replaced palm kernel cake in diets 2 – 5. Each treatment was replicated three times with 10 birds per replicate, arranged in completely randomized design (CRD). Diets were both isoenergetic and isonitrogenous. The experiment lasted for 4 weeks during the finisher phase. Feed and water were given ad libitum. At the end of 4 weeks, 3 birds from each replicate giving a total of 9 birds per treatment were slaughtered for carcass and internal organ evaluation. Result from the carcass evaluation showed that dressed carcass, breast, thigh, wing and drumstick of OA treated groups were not significantly (P>0.05) different from the control. The backcut was significantly (P<0.05) heavier in control than in AA and CA. Abdominal fat in birds fed OAs was statistically similar to the control. The liver weight was significantly (P<0.05) reduced by BA and FA while the weight of spleen was reduced (P<0.05) by all the OAs. The caecum and the large intestine were significantly (P<0.05) enlarged in the control. There was non effect (P>0.05) on other internal organs.

Synergistic Impacts of Organic Acids and pH on Growth of Pseudomonas aeruginosa: A Comparison of Parametric and Bayesian Non-parametric Methods to Model Growth.

Different weak organic acids have significant potential as topical treatments for wounds infected by opportunistic pathogens that are recalcitrant to standard treatments. These acids have long been used as bacteriostatic compounds in the food industry, and in some cases are already being used in the clinic. The effects of different organic acids vary with pH, concentration, and the specific organic acid used, but no studies to date on any opportunistic pathogens have examined the detailed interactions between these key variables in a controlled and systematic way. We have therefore comprehensively evaluated the effects of several different weak organic acids on growth of the opportunistic pathogen Pseudomonas aeruginosa. We used a semi-automated plate reader to generate growth profiles for two different strains (model laboratory strain PAO1 and clinical isolate PA1054 from a hospital burns unit) in a range of organic acids at different concentrations and pH, with a high level of replication for a total of 162,960 data points. We then compared two different modeling approaches for the interpretation of this time-resolved dataset: parametric logistic regression (with or without a component to include lag phase) vs. non-parametric Gaussian process (GP) regression. Because GP makes no prior assumptions about the nature of the growth, this method proved to be superior in cases where growth did not follow a standard sigmoid functional form, as is common when bacteria grow under stress. Acetic, propionic and butyric acids were all more detrimental to growth than the other acids tested, and although PA1054 grew better than PAO1 under non-stress conditions, this difference largely disappeared as the levels of stress increased. As expected from knowledge of how organic acids behave, their effect was significantly enhanced in combination with low pH, with this interaction being greatest in the case of propionic acid. Our approach lends itself to the characterization of combinatorial interactions between stressors, especially in cases where their impacts on growth render logistic growth models unsuitable.

Zinc Removal from Basic Oxygen Steelmaking Filter Cake by Leaching with Organic Acids

The dust generated from the basic oxygen steelmaking (BOS) process is a waste material mainly containing iron that cannot be recycled owing to its high zinc content. In this study, the leaching effects of different organic acids are compared, with the aim of determining an acid that selectively leaches and removes zinc from BOS dust, so that the waste material can be recycled into ironmaking and steelmaking processes in order to substitute part of the raw materials of steelmaking. The dust used in this study was scrubbed and collected in the form of a filter cake. The acids tested were oxalic, citric, acetic, propionic, butyric, and valeric acids. Butyric acid was found to be the most effective, with a high zinc extraction level of 49.7 pct and a low iron level of only 2.5 pct. Oxalic acid was the least effective leaching reagent for both zinc and iron extractions, owing to the formation of zinc and iron oxalate precipitates following metal dissolution. The filter cake and leached residues were characterized by chemical analysis, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy with energy dispersive spectroscpopy.

Synthesis of Iron Oxide Nanoclusters by Thermal Decomposition.

Herein, we report a novel one-step solvothermal synthesis of magnetite nanoclusters (MNCs). In this report, we discuss the synthesis, structure, and properties of MNCs and contrast enhancement in T2-weighted MR images using magnetite nanoclusters. The effect of different organic acids, used as surfactants, on the size and shape of MNCs was investigated. The structure and properties of samples were determined by magnetic measurements, TGA, TEM, HRTEM, XRD, FTIR, and MRI. Magnetic measurements show that obtained MNCs have relatively high saturation magnetization values (65.1-81.5 emu/g) and dependence of the coercive force on the average size of MNCs was established. MNCs were transferred into an aqueous medium by Pluronic F-127, and T2-relaxivity values were determined. T2-Weighted MR phantom images clearly demonstrated that such magnetite nanoclusters can be used as contrast agents for MRI.

Morphology‐Controlled Preparation of α‐Calcium Sulfate Hemihydrate from Phosphogypsum by Semi‐Liquid Method

AbstractPhosphogypsum (PG), a by‐product of phosphoric acid industry, causes environmental issues. In this paper, PG was effectively transformed into alpha‐calcium sulfate hemihydrate (ɑ‐CSH) via a semi‐liquid method. The phase evolution and the effects of different organic acids and pH values on crystal morphology of the α‐CSH were investigated by SEM, XRD and EDS. The properties of the prepared α‐CSH with different aspect ratio were also compared. The results indicate that PG can be successfully transformed into α‐CSH by the semi‐liquid method at 140 °C for 3.0 h. The morphology of the produced α‐CSH is significantly influenced by the concentrations of organic acid and pH value. α‐CSH crystal with well‐morphology is obtained under the condition of 0.1 wt.% maleic acid and pH = 7.0. The obtained α‐CSH with uniform particle size has the aspect ratio of 1.2. The 2 h and 3 d bending/compressive strengths of the hardened paste prepared from the α‐CSH reach 6.4/20.6 MPa and 10.5/43.7 MPa respectively, which are comparable to those of the commercial α‐CSH. Moreover, the lower aspect ratio of ɑ‐CSH results in more compact microstructure and higher mechanical strengths of the hardened paste.

Effects of low molecular weight organic acids and fulvic acid on 2,4,4′-trichlorobiphenyl degradation and hydroxyl radical formation in a goethite-catalyzed Fenton-like reaction

The effects of different organic acids on 2,4,4′-trichlorobiphenyl (PCB28) degradation, H2O2 decomposition and OH formation in a goethite-catalyzed Fenton-like reaction were investigated at different pH and initial organic acid concentrations. In general, organic acid addition had a similar effect on PCB28 degradation and OH formation, but there was a significant difference between its effect on PCB28 degradation and H2O2 decomposition. This indicates that OH was responsible for PCB28 degradation in the heterogeneous Fenton reaction. Oxalic, citric, malic and succinic acid addition decreased PCB28 degradation, H2O2 decomposition and OH formation. Their inhibitory effect followed the order oxalic acid>citric acid>malic acid>succinic acid, according to their sorption affinity for a goethite surface. Catechol and gallic acid addition had a considerable inhibitory effect on PCB28 degradation and OH formation, and the opposite effect was observed with 2,6-dimethoxylphenol and caffeic acid addition, although the addition decreased the H2O2 decomposition. The addition of low-concentration fulvic acid (FA) could promote PCB28 degradation and OH formation at pH 3 and pH 7, but an inhibitory effect was observed with increasing concentrations of FA. The inhibitory effect of added FA on H2O2 decomposition increased with decreasing pH and with increasing FA concentrations.

Effect of Different Organic Acids for Heavy Metal Extraction from Pb, Zn and Cd Contaminated Soil

The aim of this work was to select organic aids with most obvious activation to Pb, Zn and Cd compound in contaminated soil in order to assist phytoremediation. Five kinds of low-molecular organic acid were used to leach the soils, and then heavy metal contents in the filtrate were measured. The effect of organic acids was evaluated in mobilization of heavy metals and their impacts on soil pH were discussed. With increasing concentrations of organic acids, the activation effect increased while soil pH had negative correlation. Citric acid had the most obvious activation compared with the other four organic acids. The maximum extraction rate of Cd, Zn of citric acid was shown at concentration of 50 mmol·kg-1, and that of Pb was at 40 mmol·kg-1. The extraction rates were 7.36%, 28.79%, 0.56%, respectively. The activation effects of heavy metals in soil were Zn>Cd>Pb.

Effects of different organic acids on performance, ileal microflora, and phosphorus utilization in laying hens fed diet deficient in non-phytate phosphorus

The present study was conducted to investigate the effect of dietary supplementation of organic acids (OA) on performance and phytate phosphorus utilization in laying hens fed diets with different non-phytate phosphorus (NPP) levels. A total of 240 Hy-Line W-36 laying hens, 32-wk-old, were randomly allocated into the 8 dietary treatments with 5 cage replicates of 6 birds each. The main trial period lasted for 10 wk (34–44 wk of age), following a 2 wk adaptation period (32–34 wk of age). Dietary treatments consisted of a 4×2 factorial arrangement of treatments, including 4 supplemental OA (control, citric, butyric, or fumaric acids, 5g/kg of diet) and 2 different NPP levels (60 or 100% of Hy-Line W-36 recommended values). Results showed that dietary OA supplementation increased (P<0.05) egg production percentage, with the greatest values assigned to the hens fed citric and butyric acids-supplemented diets. Reducing dietary NPP level resulted in a marked decrease in egg production in control hens, while OA supplementation of the NPP-deficient diet could maintain egg production and egg mass, resulted in the significant (P<0.05) OA×NPP interactions. Although feed intake was not affected by dietary treatments, supplemental OA improved (P<0.05) feed conversion ratio in NPP-deficient hens (OA×NPP, P<0.05). Dietary OA supplementation increased (P<0.05) eggshell thickness; however, it had no marked impact on shell breaking strength. Serum lipid metabolites were influenced by dietary OA supplementation, so that supplemental OA decreased (P<0.01) serum cholesterol level and increased (P<0.001) serum high-density lipoproteins. Feeding the NPP-deficient diet decreased (P<0.01) tibia ash and increased (P<0.001) serum alkaline phosphatase activity. On the other hand, dietary supplementation of fumaric acid increased (P<0.01) tibial ash and Ca contents compared to the control hens. Tibia P content was lower (P<0.05) in hens fed the NPP-sufficient diet. Inclusion of citric acid into the NPP-deficient diet increased tibia P, resulted in a significant (P<0.001) OA×NPP interaction. Dietary supplementation of OA reduced (P<0.01) ileal enumeration of Salmonella, and the lowest (P<0.05) Escherichia coli count was observed for hens supplemented with butyric acid. The present findings indicate that dietary OA supplementation can increase egg production, egg mass, and eggshell thickness in hens fed the NPP-deficient diet. The beneficial impact of citric acid on tibia P content of NPP-deficient hens suggests that supplemental OA could improve P utilization even in young laying hens.

Dietary effects of different organic acids on growth and nutrient digestibility of broiler

An experiment was conducted to determine the effect of organic acids (acetic, butyric, citric and formic acids) on growth and nutrient digestibility of broilers. One hundred fifty (150) day old Hubbard chicks were used. There were five dietary treatments such viz Diet 1 as control contained no organic acid, diets 2, 3, 4, and 5 contained 0.25% acetic, butyric, citric and formic acids, respectively. Each treatment was replicated three times having 10 birds arranged in completely randomized design (CRD). Feed and water were given ad libitum. Feeding of organic acid diets lasted for 7 weeks starting from the second week. At the starter phase, formic acid improved live weight. Feed and water intakes were significantly (P&lt;0.05) reduced by butyric acid. Feed: gain ratio was improved by formic acid. At the finisher phase, live weight was significantly (P&lt;0.05) improved by the acids except butyric acid. Feed intake, daily gain and feed: gain ratio were not significant (P&gt;0.05). Crude protein and ether extracts digestibility were improved by all the organic acids (P&lt;0.05). It is therefore concluded that 0.25% formic acid could be added to broiler diets.Bang. J. Anim. Sci. 2016. 45 (2): 10-17

Comparative Effect of Different Organic Acids (Benzoic, Acetic and Formic) on Growth Performance, Immune Response and Carcass Traits of Broilers

An experiment was conducted to study the effect of benzoic, acetic and formic acid supplementation on growth performance and carcass characteristics of broilers. One hundred fifty, a day-old broiler chicks were procured from a local commercial hatchery and randomly divided into four treatment groups. Each group having thirty chicks was further sub divided into three replicates, ten chicks each. Group A, B, C were supplemented with 0.5% benzoic, acetic and formic acid, respectively, while group D was control. Data on growth performance in terms of body weight, feed intake and feed conversion ratio was noted on weekly basis. Blood sample were collected (2 birds/replicate) at 28 and 35 day of experiment to check the antibody titer against Newcastle disease and Infectious Bursal disease, respectively. Comparison by LSD test among different treatments showed that maximum weight gain was found in treatment C (formic acid) and minimum in D (control group). Significantly best feed conversion ratio was found in treatment C (formic acid) and poorer was found in treatment D (control group). The maximum significant value of IBD antibody titer (96.00GMT) was found in treatment C (formic acid) and minimum (41.67GMT) in treatment A (benzoic acid). However, the best result against ND antibody titer (104.67GMT) was found in treatment D (control group). Statistical analysis of the data on dressing percentage, breast meat, thigh meat and giblet organs weight e.g. liver, heart and gizzard revealed non-significant effect among the dietary treatment group. It was concluded that addition of organic acids (benzoic, acetic and formic) is helpful to improve weight gain, feed intake and feed conversion ratio of the birds, these factors are specifically related to efficient and economical broiler production.

Effects of foliar application of organic acids on alleviation of aluminum toxicity in alfalfa

AbstractOrganic acids (OA) may affect plant resistance to aluminum (Al) toxicity in acidic soils. However, limited information is available on the effects of different organic acids on Al resistance in alfalfa. We investigated the effects of foliar application of organic acids (succinic acid, citric acid, malic acid, and oxalic acid) to alfalfa (Medicago sativa L.) under Al stress. Seedlings were grown in pH 4.5 nutrient solution containing Al at 0 or 100 μM, and were sprayed with water or 100 μM of oxalic acid, malic acid, citric acid, or succinic acid every 3 d during a 10 d experiment. Aluminum stress caused significant reduction in alfalfa growth (reflected by above‐ground biomass, root weight and root length), root activity, mineral nutrient concentrations (Ca, K, Mg, Mn and Zn), and a significant increase in leaf membrane lipid peroxidation. Foliar application of the four organic acids, especially succinic acid, alleviated Al toxicity, as demonstrated by the increase in plant growth and root activity, as well as reduction in lipid peroxidation. Oxalic acid and malic acid treatments significantly increased oxalate exudation and decreased Al concentration in roots exposed to Al stress. Succinic acid treatment significantly increased accumulation of all four organic acids in roots, accumulation of Ca, K, Mg, Mn and Zn, and up‐regulated the gene transcription of malate dehydrogenase (MDH) and phosphoenolpyruvate carboxylase (PEPC) in roots. Our results suggest that the promotion of oxalate exudation from roots through exogenous application of oxalate and malate could contribute to the improvement in Al resistance of alfalfa, and the positive effects of exogenous application of succinate on Al resistance may be associated with the increased endogenous accumulation of all four organic acids in roots, which may constitute an organic‐acid detoxification system in alfalfa.

Combined ultrasonic and bioleaching treatment of hospital waste incinerator bottom ash with simultaneous extraction of selected metals

The mineralogy, as well as elemental composition, of the incinerated hospital waste (HW) ashes are not well known and need to be investigated for the safe handling and disposal of such ash. A study was conducted to investigate the chemical composition, mineralogy and bioleaching of selected metals from incinerated HW bottom ash using Aspergillus niger under the combined effect of ultrasonic radiation. Different techniques were utilized to determine the elemental composition (Electron Dispersive X-ray Spectroscopy [EDX], atomic absorption spectrophotometry, inductively coupled plasma-optical emission spectroscopy, ultraviolet-visible light spectrophotometer) and mineralogy (X-ray Diffraction) of the raw sample, as well as the bioleached samples. Chemical leaching tests were performed to determine the effect of different organic acids on metals dissolution. Microbes were tested for acid production and leaching capabilities of selected metals from medical waste (MW) bottom ash. Wet chemical and EDX analyses showed that the ash was enriched with metallic elements like Na, K, Ca, Fe and Al with a concentration range of 22–115 (g/kg). Furthermore, the ash contained heavy metals such as Cu, Cr, Ni, Sn and Ti in the range of 0.51–21.74 (mg/kg). Citric and oxalic acids generated by fungi could be important leaching agents acting to dissolve these metals. Under ultrasonic treatment, metals dissolution by the acidic metabolites was at its maximum after just 9 d of leaching. The results showed that the dissolution of metals was much higher in citric and oxalic acid than with other acids. Extraction of metals from incinerated MW ash indicated that this ash may be a potential source of metals in the future.

Study on the control of pore sizes of membranes using chemical methods Part IV. The role of organic acids

In this paper, polyacrylonitrile (PAN) porous membranes were prepared via combination of phase inversion and chemical reaction method with different organic acids (glacial acetic acid, fumaric acid and citric acid) as additive. The experimental results showed that pure water flux of the membrane decreased with increase in polymer concentration and membrane prepared with moderate polymer concentration presented better performance. The influence of different organic acids on the properties of the casting solution was examined by viscosity, and the relationship between viscosity and membrane performance was analyzed. The prepared membranes were characterized in terms of pure water flux, retention, pore size distribution and scanning electron microscopy (SEM) observation. It was found that the membrane, prepared with glacial acetic acid, has the typical asymmetric membrane morphology with optimal combination of narrow pore size distribution and better permeability. The contribution of different organic acids in casting solution to membrane performance during chemical reaction was quantitatively analyzed, and the effects of different organic acids on membrane structures were discussed. Meantime, compaction analysis demonstrated that the membranes prepared with glacial acetic acid had improvement in resistance against compaction compared to that prepared with other acids.