Final pH Research Articles

Removal of triclosan from aqueous solution via adsorption by kenaf‐derived biochar: Its adsorption mechanism study via spectroscopic and experimental approaches

Biochars derived from kenaf were synthesized to adsorb triclosan from an aqueous solution. The triclosan adsorption mechanism of the biochars pyrolyzed at various temperatures (300, 400, 600, and 750 °C) was explored using physical/chemical analyses (FE-SEM, EDS, EA, XRF, pHpzc, N2 adsorption-desorption, SAXS, ATR-FTIR, and XPS). The triclosan adsorption by the kenaf biochar increased as the pyrolysis temperature increased, except for 450 °C, which showed the lowest adsorption capacity. The kenaf biochar synthesized at 750 °C (KNF-750) exhibited the highest adsorption capacity owing to its high aromatic moiety and large specific surface area. Kinetic adsorption by KNF-750 was well fitted with the pseudo-second-order model, with equilibrium attained within 3 h. The maximum triclosan adsorption capacity of KNF-750 obtained from the Langmuir model with a high correlation coefficient was 77.4 mg/g. Triclosan adsorption sharply decreased at an initial solution pH of 5 because a final solution pH higher than 9 caused dissociation of triclosan. A 90% removal of triclosan was achieved with 4 g/L of KNF-750. The adsorption of triclosan was endothermic, with an enthalpy change of 32.8 kJ/mol. XPS analysis proved that triclosan was adsorbed on the surface of biochar by the disappearance of inorganic Cl and the appearance of organic Cl.

Hydrolysis of lignocellulosic forages by Trichoderma longibrachiatum isolate from bovine rumen

Fungi of the genus Trichoderma hydrolyze lignocellulosic materials, thus promoting the production of fermentable sugars. In the present study, the production of cellulases by Trichoderma longibrachiatum from ruminal fluid was evaluated in submerged fermentation of Urochloa decumbens hay (UD) or sugarcane bagasse (SB). Moreover, the biomass of this fungus was analyzed by supplementing it with urea or ammonium sulfate and with two buffer systems for the production of cellulases by T. longibrachiatum using SB or UD. The fermentations were carried out in test tubes containing Sabouraud broth, and the carbon source was packed in nonwoven fabric sachets. The fermentations were performed at 39 °C for 10 days. The factorial design was completely randomized, and the final pH, fungal biomass, substrate dry matter degradation, total protein, and cellulolytic enzymes were evaluated after the fermentation process. The fungal development was better in the medium supplemented with ammonium sulfate than that supplemented with urea, and it showed better degradation of UB than SB. The evaluated isolate promoted better protein synthesis during fermentation of SB buffered with sodium acetate; however, the medium containing UB produced higher concentrations of total cellulase, carboxymethylcellulase, and avicelase than the medium containing SB. Thus, rapid cellulose production by this fungus may aid in the hydrolysis of lignocellulosic materials for animal feed supplementation for ruminants; furthermore, the use of these enzymes for biotechnological purposes is promising.

Hydrothermal Syntheses of Uranium Oxide Hydrate Materials with Sm(III) Ions: pH-Driven Diversities in Structures and Morphologies and Sm-Doped Porous Uranium Oxides Derived from Their Thermal Decompositions.

We report the hydrothermal syntheses of three uranyl oxide hydroxy-hydrate (UOH) materials containing Sm(III) ions (UOH-Sm) by controlling the solution pH and a new way to make Sm-doped porous uranium oxides with different U-to-Sm atomic ratios via their thermal decompositions. While layer-structured UOH-Sm phases with U-to-Sm atomic ratios of 1 (UOH-Sm1) and 4 (UOH-Sm2) were obtained from the reaction of schoepite and samarium nitrate with final solution pH values of over 4, similar reactions without pH adjustment with final solution pH values of less than 4 led to the formation of a uranyl oxide framework (UOF-Sm) with a U-to-Sm atomic ratio of 5.5. The crystal structure of compound UOF-Sm was revealed with synchrotron single-crystal X-ray diffraction and confirmed with transmission electron microscopy. The two-dimensional uranyl oxide hydroxide layers, similar to that for β-U3O8, are linked by double pentagonal uranyl polyhedra to form a three-dimensional framework with Sm(III) ions in the channels. Scanning electron microscopy characterization revealed nanoplate crystal morphologies for the two UOH-Sm phases, in contrast to the needle morphology for UOF-Sm. Subsequent thermal treatments led to the formation of Sm-doped uranium oxides, maintaining the original crystal shapes and U-to-Sm ratios but with nanopores. This work demonstrated that the hydrothermal synthesis conditions, especially fine-tuning of the solution pH, have a significant impact on the uranium hydrolysis, thus leading to well-defined products. This will facilitate the targeted syntheses of UOH phases with lanthanide (Ln) ions and explore the subsequent applications of these materials and Ln-doped porous uranium oxides as potential nuclear or functional materials.

A simulation and experimental study of electrochemical pH control at gold interdigitated electrode arrays

In electroanalysis, solution pH is a critical parameter that often needs to be tailored and controlled for the detection of particular analytes. This is most commonly performed by the addition of chemicals, such as strong acids or bases. Electrochemical in-situ pH control offers the possibility for the local adjustment of pH at the point of detection, without the need for additional reagents. Finite element analysis (FEA) simulations have been performed on interdigitated electrodes, to guide experimental design in relation to both electroanalysis and in-situ control of solution pH. No previous model exists that describes the generation of protons at an interdigitated electrode arrays in solution with one comb acting as a protonator, and the other as the sensor. In this work, FEA models are developed to provide insight into the optimum conditions necessary for electrochemical pH control. The magnitude of applied galvanostatic current has a direct relation to the flux of protons generated and subsequent change in pH. Increasing the separation between the electrodes increases the time taken for protons to diffuse across the gap between the electrode combs. The final pH achieved after 1 second, at both protonator and sensor electrodes, was shown to be largely uninfluenced by a solution's initial pH. The impact of buffer concentration was also modelled and investigated. In practice, the pH at the electrode surface was probed by means of cyclic voltammetry, i.e., to identify the potential of the gold oxide reduction peak. A pH indicator, methyl red, was used to visualise the solution pH change at the electrodes, comparing well with the model's prediction. Finally, we show that in-situ pH controlled detection of mercury in water, using square wave stripping voltammetry, is almost identical to samples acidified to pH 3.5 using nitric acid.

Biodegradability of a bioplastic film from tamarind xyloglucan in composting bioreactors

Plastic is used excessively due to its excellent properties and its low cost. This has led to the ubiquitous accumulation of waste as it takes a very long time to biodegrade. Until now, several research projects have developed different biodegradable plastics, and the tests to validate them are still being undertaken. In this research, a biodegradability test was performed on a bioplastic synthesized from tamarind xyloglucan and ethyl acrylate (b-XgT), designed to be a substitute for polystyrene. A sample of the b-XgT was composted in laboratory conditions and CO2 release measurements were made. The results showed a biodegradation time of 18 days with a loss of mass of 40.3% and a final pH of 7.1. The b-XgT was found to be biodegradable of the compostable type through the anaerobic route, which promotes the digestion of compounds such as xylose that contribute to the degradation of the whole polymer.

EPR Study of KO2 as a Source of Superoxide and •BMPO-OH/OOH Radical That Cleaves Plasmid DNA and Detects Radical Interaction with H2S and Se-Derivatives.

Superoxide radical anion (O2•−) and its derivatives regulate numerous physiological and pathological processes, which are extensively studied. The aim of our work was to utilize KO2 as a source of O2•− and the electron paramagnetic resonance (EPR) spin trapping 5-tert-butoxycarbonyl-5-methyl-1-pyrroline N-oxide (BMPO) technique for the preparation of •BMPO-OOH and/or •BMPO-OH radicals in water solution without DMSO. The method distinguishes the interactions of various compounds with •BMPO-OOH and/or •BMPO-OH radicals over time. Here, we show that the addition of a buffered BMPO-HCl mixture to powdered KO2 formed relatively stable •BMPO-OOH and •BMPO-OH radicals and H2O2, where the •BMPO-OOH/OH ratio depended on the pH. At a final pH of ~6.5–8.0, the concentration of •BMPO-OOH radicals was ≥20 times higher than that of •BMPO-OH, whereas at pH 9.0–10.0, the •BMPO-OH radicals prevailed. The •BMPO-OOH/OH radicals effectively cleaved the plasmid DNA. H2S decreased the concentration of •BMPO-OOH/OH radicals, whereas the selenium derivatives 1-methyl-4-(3-(phenylselanyl) propyl) piperazine and 1-methyl-4-(4-(phenylselanyl) butyl) piperazine increased the proportion of •BMPO-OH over the •BMPO-OOH radicals. In conclusion, the presented approach of using KO2 as a source of O2•−/H2O2 and EPR spin trap BMPO for the preparation of •BMPO-OOH/OH radicals in a physiological solution could be useful to study the biological effects of radicals and their interactions with compounds.

Inconsistent effects of species diversity and N fertilization on soil microbes and carbon storage in perennial bioenergy cropping systems

AbstractPositive relationships between plant species diversity, soil microbial function and nutrient cycling have been well documented in natural systems, and these relationships have the potential to improve the production and sustainability of agroecosystems. Our objectives were to study the long-term effects of planted species composition and nitrogen (N) fertilization on soil microbial biomass C, extracellular enzyme activity, changes in total soil C, soil fertility and aboveground biomass yield in mixtures of native prairie species managed with and without N fertilizer for bioenergy production at four sites in Minnesota (MN), USA. Species were sown into mixture treatments and composition was not maintained (i.e., no weeding) throughout the duration of the study. Species mixture treatments at establishment included a switchgrass (Panicum virgatum L.) monoculture (SG), a four-species grass mixture (GM), an eight-species legume/grass mixture (LG) and a 24-species high diversity forb/legume/grass mixture (HD). Species diversity and aboveground productivity were similar for most mixture treatments at final sampling after 11 or 12 years of succession. Despite this homogenization of productivity and diversity throughout the study, the effects of planted species diversity and a decade of succession resulted in some differences in soil variables across species mixture treatments. On a peat soil in Roseau, MN, soil enzyme activities including β-glucosidase (BG), cellobiohydrolase (CBH) and phosphatase (PHOS) were highest in HD compared to GM treatments. On a sandy soil at Becker, MN, total soil C increased in all treatment combinations at the 0–15 and 15–30 cm depth intervals, with SG showing greater increases than HD at the 15–30 cm depth. Final soil pH also varied by species mixture at the Becker and Roseau sites, but differences in treatment comparisons varied by location. Nitrogen fertilization did not affect any response variable alone, but interacted with species mixture treatment to influence PHOS and total soil C at Becker. The inconsistent effects of species mixture and N fertilization on soil biological and chemical properties observed across sites highlight the importance of local soil and climate conditions on bioenergy and ecosystem service provisioning of perennial bioenergy cropping systems.

Palmitic acid sophorolipid biosurfactant: from self-assembled fibrillar network (SAFiN) to hydrogels with fast recovery.

Nanofibres are an interesting phase into which amphiphilic molecules can self-assemble. Described for a large number of synthetic lipids, they were seldom reported for natural lipids like microbial amphiphiles, known as biosurfactants. In this work, we show that the palmitic acid congener of sophorolipids (SLC16:0), one of the most studied families of biosurfactants, spontaneously forms a self-assembled fibre network (SAFiN) at pH below 6 through a pH jump process. pH-resolved in situ small-angle X-ray scattering (SAXS) shows a continuous micelle-to-fibre transition, characterized by an enhanced core-shell contrast between pH 9 and pH 7 and micellar fusion into a flat membrane between pH 7 and pH 6, approximately. Below pH 6, homogeneous, infinitely long nanofibres form by peeling off the membranes. Eventually, the nanofibre network spontaneously forms a thixotropic hydrogel with fast recovery rates after applying an oscillatory strain amplitude out of the linear viscoelastic regime: after being submitted to strain amplitudes during 5 min, the hydrogel recovers about 80% and 100% of its initial elastic modulus after, respectively, 20 s and 10 min. Finally, the strength of the hydrogel depends on the medium's final pH, with an elastic modulus fivefold higher at pH 3 than at pH 6. This article is part of the theme issue 'Bio-derived and bioinspired sustainable advanced materials for emerging technologies (part 1)'.

Plant growth-promoting properties of extracts produced by fermenting the freshwater macroalga, Oedogonium intermedium

Extracts produced from marine macroalgal biomass promote plant growth, improve yield, and increase the tolerance of plants to physiological stressors. Most of these extracts are produced with dried macroalgal biomass as their stock material, and use processing techniques that cause considerable modification to the original biomass and require a substantial investment in energy and equipment. As such, the aim of this study was to determine whether the freshwater macroalga Oedogonium intermedium could be successfully fermented using freshly harvested biomass, such that this biomass was transformed into a stable, non-offensive product that had plant growth-promoting properties. This was demonstrated by manipulating the starting conditions (presence or absence of salinity, molasses, and microbes) of the fermentations. The liquid extracts had a positive effect on the growth of mung bean plants compared with the positive controls – a soluble plant fertiliser and a commercially available fermented seaweed product. The most effective extract (Oedo 4), which was fermented in 20 ppt saltwater with the addition of molasses, demonstrated a 28.9–48.6% larger total plant dry weight than the commercial controls, respectively. Notably, extracts fermented in 20 ppt saltwater resulted in larger quantities of N, P, K, Ca, and Fe than those fermented in freshwater, while extracts fermented with molasses had the lowest final pH (<4), resulting in a stable extract with non-offensive odours that were not particularly strong. This study demonstrates the viability of producing fermented extracts directly from the freshly harvested biomass of a freshwater macroalga, and that those extracts have plant growth-promoting properties.

Biochemical Properties Affecting the Nutritional Quality, Safety, and Aroma of Dry-Cured Products Manufactured from Meat of Rare Native Pig Breeds.

The aim of study was to compare the biochemical properties affecting the nutritional quality, safety, and aroma of dry-cured products manufactured from valuable meat of rare native pig breeds: Pulawska (Pul) and Zlotnicka Spotted (ZS). The count of lactic acid bacteria (4.4 log cfu/g) and the release of palmitic (23.1% and 25.9%), oleic (44.1% and 42.2%), and linoleic acids (8.3% and 7.8%), as well as arginine (30.0 and 44.3 mg/kg), histidine (25.8 and 20.6 mg/kg), and lysine (26.8–22.9 mg/kg), shaped the final pH (5.3 and 5.4) in Pul and ZS products during the 4 week maturing, respectively. Lastly, Pul and ZS meat differed in the proportion of decanoic, lauric, stearic, arachidic, and conjugated linoleic acids. The high content of putrescine (23.7 mg/kg), cadaverine (54.3 mg/kg), and tyramine (57.2 mg/kg), as well as a twofold greater share of histamine (163.2 mg/kg) and tryptamine (9.1 mg/kg), indicated a more advanced decarboxylation of ZS meat. Volatile compounds differentiating Pul and ZS meat were primarily hexanal, 3-hydroxybutan-2-one, phenylacetalaldehyde, 2,3-dimethyl-2-cyclopenten-1-one, 2-cyclopenten-1-one, and 3-methyl- and 2-cyclopenten-1-one. Most marked volatile compounds were obtained as a result of microbial activity (acetic acid, 3-methylbutan-1-ol, ethanol, acetone, and 3-hydroxybutan-2-one), advanced lipid oxidation, and decomposition of secondary oxidation products (hexanal, phenylacetaldehyde, and 2-cyclopenten-1-one).

Removal of p-arsanilic acid and phenylarsonic acid from water by Fenton coagulation process: influence of substituted amino group

Phenylarsonic acid compounds, which were widely used in poultry and swine production, are often introduced to agricultural soils with animal wastes. Fenton coagulation process is thought as an efficient method to remove them. However, the substituted amino group could apparently influence the removal efficiency in Fenton coagulation process. Herein, we investigated the optimal conditions to treat typical organoarsenic contaminants (p-arsanilic acid (p-ASA) and phenylarsonic acid (PAA)) in aqueous solution based on Fenton coagulation process for oxidizing them and capturing the released inorganic arsenic, and elucidated the influence mechanism of substituted amino group on removal. Results showed that the pH value and the dosage of H2O2 and Fe2+ significantly influenced the performance of the oxidation and coagulation processes. The optimal conditions for removing 20 mg L-1-As in this research were 40mg L-1 Fe2+ and 60mg L-1 H2O2 (the mass ratio of Fe2+/H2O2 = 1.5), initial solution pH of 3.0, and final solution pH of 5.0 adjusting after 30-min Fenton oxidation reaction. Meanwhile, the substituted amino group made p-ASA much more easily be attacked by ·OH than PAA and supply one more binding sites for forming complexes with Fe3+ hydrolysates, resulting in 36% higher oxidation rate and 7% better coagulation performance at the optimal conditions.

The effect of nanosecond pulsed electric field on the production of metabolites from lactic acid bacteria in fermented watermelon juice

Lactic acid fermentation offers a processing alternative for preservation of watermelon juice, which is sensitive to heat, oxygen, and light. In this study, 8.8 × 107 CFU/mL of Lactobacillus plantarum DSM 9843 in MRS broth was inoculated in 9.9 mL of sterilized watermelon juice. Nanosecond-pulsed electric field was applied during the log growth phase of the bacteria. An 19% increase in L-lactic acid, 6.8% increase in D-lactic acid and 15% increase in acetic acid were observed over control. The final pH was 3.8. These increased levels of metabolites were dependent on the applied voltages (L-lactic acid: 5.0 kV 700 pulses, D-lactic acid: 4.5 kV 700 pulses and acetic acid: 4.5 kV 1000 pulses). The nsPEF treatment did not affect the viability of the cells and sufficient numbers remained in the product after fermentation (1.6 × 109 CFU/mL in average). These results suggest that the metabolism of lactic acid bacteria was stimulated by the PEF treatment.

Rainfer: fertilizer production using rainwater as raw material

Shortly after the rain falls to the surface of the soil, the water flows into the water body or seeps into the ground without being optimally utilized. The low chemical and physical components are the main drawbacks of rainwater utilization. The raw material for fertilizer in this research is rainwater, so we call it rain fertilizer (rainfer). The main components of the additive are Bryophyta, sp, monosodium glutamate, hydrated lime, sodium chloride. They are added to enrich the physical and chemical components. The rainfer reactor is cylindrical with a maximum capacity of 70 liters. As much as 35 litres of rainwater plus additive is put into the reactor and stirred using a pump for 15 minutes until homogeneous. Let the mixture sit for 7 x 24 hours. The results showed that the addition of additives succeeded in increasing the parameters of TDS and conductivity respectively by 98.68% and 99.03%. The concentration of nitrate as nitrogen increased by 96.54%, from 1.13 mg/L to 32.67 mg/L. The final pH was 7.78, total P was 78.47 mg/L, total K was 0.03 mg/L, and heavy metal Cu was 0.06 mg/L. The level of toxicity based on the germination index value was 70.16% compared to the control, which is equivalent to mature and stable compost. The addition of additives can improve the quality of rainwater based on physical, chemical, and non-toxic parameters.

Fatty acid profilies and some meat quality traits at different slaughter weights of Brown Swiss bulls

This research was done to detect some meat quality traits and tissue fatty acid combination of the longissimus dorsi thoracis (LT) muscle of Brown Swiss bulls at the different slaughter weights (SW). The animal material of the study comprised 20 Brown Swiss bulls. In the study, Brown Swiss bulls were divided into two groups according to their SW as low (LSW (n = 10); 431-503kg) and high (HSW (n = 10); 504-583kg). In the study, the LSW group showed the lowest final pH value (pHF) (5.44) (P < 0.05). As the SW increase, the L* (lightness) value decreased in the LT muscle of Brown Swiss bulls (P > 0.05). In the research, the differences observed between the SW groups considering a* (redness) and C (chroma) values were found significant (P < 0.05). LT muscle water holding capacity (PL) decreased (P < 0.01) with increasing slaughter weight. In the study, the differences observed between SW groups in terms of drip losses (DL) after 3-day (DRP3) and 7-day (DRP7) storages and cooking losses (CL) determined were found insignificant (P > 0.05). Freeze-thaw loss (FL) and ether extract (PEE) were found 4.35% and 1.01% higher, respectively, in the HSW group than the LSW group (P < 0.05). Cholesterol content was determined as 66.15 and 70.68mg 100g-1 meat in LSW and HSW groups, respectively. The ratios of n-6/n-3 (P < 0.05) and PUFA/SFA (P > 0.05) in the LT muscle decreased with the increase of SW. As a result, when LSW and HSW slaughter weight groups were evaluated considering the water losses causing financial losses in meat and fatty acids having beneficial effects on human health, it was seen that the LSW group came to the fore.

Assessment of temperature and acid tolerance of Bacillus subtilis isolated from a Brazilian fruit juice-added soy beverage

Bacillus subtilis is a spore-forming bacterium and an important food contaminant. The aim of this study was to analyze the ability of B. subtilis spores to survive under conditions of low pH and high temperature. The package was purchased at a local supermarket, in Uberaba, Minas Gerais. A sample was collected, diluted and plated on Brain-Heart-Infusion agar (BHI). After incubation, suspected colonies of B. subtilis were transferred to BHI agar. Cell morphology, the presence of spores and Gram stain were examined, and the isolate was identified by 16S rRNA gene sequencing . The microscope evaluation indicated the presence of spores. The thermal tolerance of the spores was evaluated by the addition of 3x109spores/mL in test tubes containing peptone water. Heat treatments were carried out at 80 and 90°C at different incubation times (0, 10, 20, 30, 40, 50 and 60 min). After heating, the tubes were cooled and the number of viable spores was determined in BHI Agar. For the analysis of spore survival, D and Z values were calculated. Tolerance to acid conditions was evaluated using BHI broth with different pH values. After incubation, the bacterial concentration was determined by determining viable cell count on BHI Agar medium. The vegetative cells were transferred to the BHI broth and the pH was adjusted to different values (3, 4 or 5). Sampling were taken 8, 12 and 24 h after incubation. The samples were serially diluted in peptone water and spread in BHI Agar to determine the viable cell count . The 16S rRNA gene sequencing indicated high similarity (99.99%) with B. subtilis. D values were 17.01 min at 80°C and 13.42 min at 90°C. The Z-value was 97.13°C. B. subtilis was not able to grow at pH 3 and pH 4, but its survival was confirmed after the growth of colonies on BHI agar. At pH 5, B. subtilis grew after 24 h and the final pH changed to 7. Our results suggest that the spores of B. subtilis isolated from fruit juice-added soy beverage are tolerant to low pH and high temperature.

PH dependent morphology and texture evolution of ZnO nanoparticles fabricated by microwave-assisted chemical synthesis and their photocatalytic dye degradation activities

ZnO nanostructures are well-known photocatalysts for the degradation of toxic organic dyes and their morphology, size, and other physicochemical properties play important roles in their photocatalytic performance. To study the effect of size, morphology, and synthesis conditions in photocatalytic performance, we synthesized ZnO nanoparticles of different morphologies through a simple microwave-assisted chemical process at different pH values of the reaction mixture. Different pH values of the reaction mixture produced ZnO nanoparticles of different morphologies and sizes. The nature of the pH controlling agent and final pH of the reaction mixture were seen to have considerable effects on the lattice parameters and microstrain of the ZnO nanocrystals, along with their photocatalytic performance. We observed that while the ZnO nanostructures synthesized at very high pH values of the reaction mixture have a high specific surface area, their photocatalytic activity is higher when they are synthesized at acidic pH or pH near the isoelectric point of ZnO. The results demonstrate that the photocatalytic activity of ZnO nanostructures not only depends on their size or specific surface area but also strongly depends on the concentration of catalytic sites at their surface.

Stability, bioavailability and antifungal activity of reuterin during manufacturing and storage of stirred yoghurt

High purity reuterin was produced by bioconversion of glycerol using Lactobacillus reuteri and was tested for its bioavailability and antifungal activity in milk and stirred yoghurt. Natamycin was used as a control. In whole milk (3.25% fat) reuterin showed significant inhibition of Rhodotorula mucilaginosa, Aspergillus niger, Penicillium chrysogenum and Mucor racemosus by agar diffusion assay. Minimal inhibitory concentrations ranging from 1.89 mm to 7.58 mm for reuterin and from 0.005 mm to 0.16 mm for natamycin were obtained using the microtitration assay. The inhibitory activity of reuterin was shown to be fungicidal; that of natamycin was fungistatic. In stirred yoghurt kept at 4 °C, addition of reuterin at 10 mm allowed total inhibition of M. racemosus and R. mucilaginosa within 1 week and reduced A. niger counts by 3 log cycles over 4 weeks. The addition of reuterin increased the final pH of the stirred yoghurt and decreased the acidity.

Solidification of municipal solid waste incineration fly ash and immobilization of heavy metals using waste glass in alkaline activation system

Hazardous heavy metals in Municipal Solid Waste Incineration (MSWI) fly ash are a threat to the environment and ecosystems. The objective of the work is to investigate the solidification of MSWI fly ash and the immobilization of the heavy metals through alkaline activation reaction with waste glass as an additive. Compressive strength measurement, X-ray diffraction (XRD), 29Si nuclear magnetic resonance spectroscopy (29Si NMR) and scanning electron microscope (SEM) were performed to evaluate the solidification effect and characterize the microstructure of alkali-activated MSWI fly ash-based mortars. The leaching test, back-scattered electron microscopy (BSE) and X-ray photoelectron spectroscopy (XPS) were conducted to determine the heavy metals' immobilization effect and their immobilization forms. It was found that waste glass addition effectively reinforced the solidification of MSWI fly ash and immobilized the heavy metals. With 40% addition of waste glass, the compressive strength reached a maximum of 3.55 MPa. The immobilization efficiency of Cr increased with the addition of waste glass, while that of Cu, Pb, Zn and Cd is dependent on the eluant final pH, which decreased with the decrease of eluant final pH. The main immobilization forms include physical encapsulation, the formation of alkaline environment and the generation of silicate compounds.

Selective Complex Precipitation for Ferro-Chrome Separation From Electroplating Sludge Leaching Solution.

In this paper, aiming at the problem of chrome-iron separation in electroplating sludge, the separation of ferrochrome by complexation and precipitation with benzoic acid as complexing agent is achieved. The optimal conditions consisted of a 1: 3 molar ratio of Fe3+: C6H5COOH, a reaction temperature of 30°C, a final pH of 2.5 and a reaction time of 2 min. The separation rate of the iron was 97.38% and the rate of loss of chromium was only 3.59%. The ferrochromium separation products were analyzed by XRD, fluorescence spectroscopy, infrared spectroscopy and H NMR Spectroscopy in order to study the mechanism of precipitation. The results showed that benzoic acid preferentially forms a complex with iron and iron benzoate precipitates with an increase pH. The iron benzoate crystals have a fine particle size, settle rapidly and are easy to filter. The separation of Cr 3+/Fe3+ was successful using our methodology.

Nutrient Removal in Sequential Batch Polishing Ponds

One of the main problems of waste stabilization ponds (WSP) is that they cannot remove nutrients when treating wastewater. Polishing ponds (PP) can efficiently remove nitrogen and phosphorus from effluents after efficient anaerobic pretreatment. It shown that the feasibility of nutrient removal is directly related to the pH that is established in the ponds. WSP normally operate at near neutral pH, but the biological processes that develop in PP tend to cause an elevation of pH and this, in turn, triggers the mechanisms of nutrient removal in ponds. In PP oxygen production by photosynthesis predominates over the oxidation of organic material. The net oxygen production has an equivalent CO2 consumption and this induces an increase in pH. The mechanism for nitrogen removal was identified as the desorption of ammonia from the liquid phase of the ponds. It was established that in ponds with a uniform concentration profile in the liquid phase the process developed in accordance with Fick’s law. The governing mechanism of phosphorus removal was precipitation with ions present in the wastewater, presumably calcium and magnesium. Polishing ponds can be operated with two different hydrodynamic regimes: flow-through (FTPP) and sequential batch (SBPP) ponds. The SBPP have the advantage that the pH elevation is more rapid, and that the final pH is higher.