Specific Release Rate Research Articles

The comparative performance study of the EF7 downsized engines; fuel economy besides CO2 reduction

Engine downsizing is considered a strategic idea in fuel economy enhancement as well as reduction. It is defined in the literature as the decrease in engine geometrical dimensions besides its performance being fixed. In this research, the Iranian gasoline-fueled national engine, EF7, has been investigated for 25% downsizing. After introducing the gasoline-fueled and CNG-fueled versions of downsized engines, their performance, besides release rates are studied in detail. A one-dimensional engine simulator coupled with a 3D-CFD model is developed to carry out such an investigation, an experimental test setup is provided to evaluate the accuracy of the provided numerical model, as well. The first version of presented downsized engines, called EF7, is a 3-cylinder engine with the same geometrical characteristics as the base engine, which is equipped with a turbo-charger and dual CVVT technologies. The EF7 is then introduced by fuel shifting to CNG as the second version of downsized engines, and finally, increasing the compression ratio, the EF7 is presented as the third version of studied-downsized engines. The results show almost the same rate of BSFC besides a 3.4% reduction in concentration for EF7, 20.6% fuel economy enhancement, besides 20.8% reduction in the specific release rate for EF7, and 28.8% fuel economy enhancement, besides 25.3% reduction in the specific release rate for EF7 in comparison with the base engine.

Anaerobic Digestion of Phosphorus-Rich Sludge and Digested Sludge: Influence of Mixing Ratio and Acetic Acid

Phosphorus is a critical influencial factor in the anaerobic digestion of phosphorus-rich sludge (PRS). The anaerobic digestion of PRS and digested sludge (DS) mixed according to different proportions was studied. The result showed that the phosphorus release rate of the mixed sludge increased with the increase in DS proportion until the DS proportion was over 50%. When the mixing ratio of PRS to DS was 3:1, the specific phosphorus release rate (SPRR) was increased by 20% and the methane production was raised to 7.39 mL/g VSS. A further experiment on the concentration of the added acetic acid indicated that the phosphorus release rate also tended to rise with the increase in acetic acid until the concentration was over 500 mg COD/L. Finally, the results of the anaerobic digestion of DS and waste activated sludge (WAS) showed that there was no typical phosphorus release in the initial stage of anaerobic digestion in WAS.

Explosion free in fire self-venting (TPRD-less) composite tanks: Performance during fire intervention

This paper describes the performance of explosion free in fire self-venting (TPRD-less) composite tanks in fires of realistic specific heat release rate (HRR/A), i.e., total fire HRR over the source area, A, of HRR/A = 1 MW/m2, during fire intervention. This breakthrough safety technology does not require thermally activated pressure relief devices (TPRD). It provides microleaks-no-burst (μLNB) performance of hydrogen storage tanks in fire. The study investigated two fire intervention strategies, i.e., removal of vehicle with μLNB tank from the fire, and extinction of fire by water. One carbon-carbon and one carbon-basalt double-composite wall tanks were assessed in the removal from fire scenario. Four carbon-basalt prototypes were studied in fire extinction scenarios. All six prototypes of 7.5 L and nominal working pressure of 70 MPa have demonstrated safe release of hydrogen through microchannels of the wall after the liner melting. The μLNB technology allows to apply standard intervention strategies and tactics.

Preparation, Characterization and Optimization of Sustained Release Matrix Tablets of Repaglinide using Box–Behnken Design

The aim of this investigation was to develop and optimize the Sustained release Matrix formulations of Repaglinide (RLD) using response surface methodology by employing a 3-factor, 3-level Box–Behnken statistical design. The independent variables studied were the amount of hydroxypropyl methylcellulose (HPMC K4M), Ethyl cellulose (EC) and PVP K30. The Swelling index (Y1), drug release at 8 hr and 12hr were the target responses. The response surface methodology and multiple response optimizations utilizing a polynomial equation were used to search for the optimal formulation with a specific release rate at different time intervals. The results showed that the effect of combination of HPMC K4M and EC was the most influencing factor on the drug release from ER matrix tablets. The mechanism of drug release from RLD Matrix tablets was dependent on the added amount of EC. Validation of the optimization technique demonstrated the reliability of the model. The optimized formulation containing 50mg of HPMC K4, 35mg of EC, and 30mg of PVP K30 was prepared according to the software determined levels. DSC and FTIR studies combined with the stability study of the optimized formulation proved the integrity of the developed formulation. The Box–Behnken experimental design facilitated the formulation and optimization of extended release hydrophilic matrix systems of RLD in a short period of time and with the fewest number of experiments. The optimized Matrix tablet of Repaglinide showed good pharmacokinetic result over conventional formulation.

Breakthrough safety technology of explosion free in fire self-venting (TPRD-less) tanks: The concept and validation of the microleaks-no-burst technology for carbon-carbon and carbon-glass double-composite wall hydrogen storage systems

The paper describes the breakthrough microleaks-no-burst (μLNB) safety technology of explosion free in fire self-venting hydrogen tanks that do not require thermally-activate pressure relief devices (TPRD). The technology implies melting of the hydrogen-tight liner before hydrogen-leaky double-composite wall loses its load-bearing ability. Hydrogen then flows through the wall's microchannels and either burns in microflames on its own or together with resin. The experimental validation of the technology is presented for 7 prototypes with the nominal working pressure of 70 MPa made of carbon-carbon or carbon-glass composites. The prototypes are fire tested at the specific heat release rate HRR/A = 1 MW/m2 characteristic for gasoline/diesel spill fires. The μLNB technology eliminates catastrophic consequences of tank rupture in fire: blast waves, fireballs, and projectiles. The technology limits hydrogen accumulation in naturally ventilated enclosures. It reduces the risk of hydrogen-powered vehicles to an acceptable level below that for fossil fuel automobiles, including underground parking and tunnels. It provides an unprecedented level of life safety and property protection.

Phosphorus Removal from Aerobic Granular Sludge: Proliferation of Polyphosphate-Accumulating Organisms (PAOs) under Different Feeding Strategies

Aerobic granular sludge (AGS) is known for high phosphorus removal from wastewaters, and phosphorus can be recovered from high phosphorus-containing waste sludge granules. This study aimed at determining the feeding strategy that provides the best performance in terms of the proliferation of polyphosphate-accumulating organisms (PAOs) and phosphorus removal. Using three AGS bioreactors, this study compared phosphorus removal and the proliferation dynamics of PAOs under three different feeding strategies: anaerobic slow feeding (R1), pulse feeding + anaerobic mixing (R2), and pulse feeding (R3). Results indicate that R1 and R2 achieved significantly higher phosphorus removal (97.6 ± 3% for R1 and 98.3 ± 1% for R2) than R3 (55 ± 11%). The anaerobic slow feeding procedure (R1) achieved the highest specific phosphorus release rate (SPRR) and specific phosphorus uptake rate (SPUR) as compared to the other two feeding conditions. 16S ribosomal ribonucleic acid (rRNA) gene sequencing assay of the microbial community for the three feeding strategies indicated that although the feeding strategy impacted reactor performance, it did not significantly alter the microbial community. The bacteria community composition maintained a similar degree of diversity. Proteobacteria, Bacteroidetes, and Verrucomicrobia were the dominant bacterial phyla in the system. Dominant PAOs were from the class Betaproteobacteria and the genera Paracoccus and Thauera. Glycogen-accumulating organisms were significantly inhibited while other less-known bacteria such as Wandonia and Hyphomonas were observed in all three reactors.

Comparative study of oregano essential oil encapsulated in halloysite nanotubes and diatomaceous earth as antimicrobial and antioxidant composites

Multifunctional composite materials with controlled release, antimicrobial and antioxidant properties were prepared through encapsulation of oregano essential oil (OEO) into diatomaceous earth (DE) and halloysite nanotubes (Hal). DE-OEO and Hal-OEO composites were compared with their physicochemical and functional properties such as the morphology and elemental analysis, zeta-potential, chemical structure, crystallinity, thermal stability, specific surface area, encapsulation efficiency, release rate, antioxidant, and antimicrobial properties. Pristine DE showed a sunflower-like shape with an average diameter of 24 μm, zeta-potential of −47.3 mV and BET of 0.87 m2/g. Whereas Hal exhibited a tubular structure with an average length of 788 nm and width of 115 nm, zeta-potential of −19.7 mV and BET of 68.5 m2/g. The morphology and crystallinity of DE and Hal did not change significantly after OEO loading, whereas FT-IR results confirmed that OEO was successfully loaded into DE and Hal. The thermal stability of OEO was improved after being encapsulated into Hal and DE. Both samples showed high antioxidant and antimicrobial activities. However, the DE-OEO sample exhibited stronger antioxidant and antimicrobial activities than Hal-OEO due to its higher encapsulation efficiency and release rate. Prepared materials can be used as a controlled-release, antioxidant, antimicrobial, nanofiller for food packaging, and drug delivery applications.

Model for Long Acting Injectables (Depot Formulation) Based on Pharmacokinetics and Physical Chemical Properties.

The objective was to develop a model to a priori identify the most suitable depot technology for a candidate based upon its therapeutic index (TI), pharmacokinetics (PK), and physical chemical properties. A depot map of release rates needed to achieve target PK in TI against release rates predicted based on intrinsic dissolution rate (IDR) and particle size (PS) clearly identified three zones: (a) products and candidates around the line of identity for which suspension is the appropriate depot technology, (b) area to the right of line of identity in which depot candidates would require a controlled release technology such as PLGA microspheres since in vivo release rate needed for PK in TI is significantly lower than predicted based on IDR and PS, and (c) area to the left of the line of identity where IDR is not sufficient to achieve target in vivo release rate for PK in TI and hence enhanced dissolution is needed such as with nanoparticles. Dose-solubility technology map of approved depot products and candidates showed clusters of products around a depot technology such as suspensions and microspheres, for drugs with high dose/low solubility and low dose/high solubility compounds, respectively. Novel PK-based computational tool showed how all combinations of depot doses and release rate constants for a candidate can be calculated to achieve plasma levels within the TI bounded by minimum effective and minimum toxic concentrations (MEC and MTC). The PK predictions for several drugs such as estradiol, risperidone, medroxyprogesterone acetate (MPA), and ziprasidone showed how these predictions can guide scientists to target specific depot doses and release rates into the depot formulation. In parallel, IDR of depot compounds clearly showed differentiation of compounds by successful depot technologies to achieve target dose and duration. For drugs with IDR between 0.1 and 1 mg/h/cm2, aqueous suspension has successfully delivered depot PK profile, while for candidates with IDRs greater than 1 mg/h/cm2, controlled release technology such as microsphere or in situ gel was required. The framework, prediction tools, and depot map will reduce the need for semi-empirical formulation work and preclinical studies to design depot formulations. Graphical Abstract.

Wood Dust Flammability Analysis by Microscale Combustion Calorimetry.

To study the practicability of a micro combustion calorimeter to analyze the calorimetry kinetics of wood, a micro combustion calorimeter with 13 heating rates from 0.1 to 5.5 K/s was used to perform the analysis of 10 kinds of common hardwood and softwood samples. As a microscale combustion measurement method, MCC (microscale combustion calorimetry) can be used to judge the flammability of materials. However, there are two methods for measuring MCC: Method A and Method B. However, there is no uniform standard for the application of combustible MCC methods. In this study, the two MCC standard measurement Methods A and B were employed to check their practicability. With Method A, the maximum specific heat release rate, heat release temperature, and specific heat release of the samples were obtained at different heating rates, while for Method B, the maximum specific combustion rate, combustion temperature and net calorific values of the samples were obtained at different heating rates. The ignition capacity and heat release capacity were then derived and evaluated for all the common hardwood and softwood samples. The results obtained by the two methods have significant differences in the shape of the specific heat release rate curves and the amplitude of the characteristic parameters, which lead to the differences of the derived parameters. A comparison of the specific heat release and the net calorific heat of combustion with the gross caloric values and heating values obtained by bomb calorimetry was also made. The results show that Method B has the potentiality to evaluate the amount of combustion heat release of materials.

N-Acetylcysteine is an effective analog of glutathione in reactions with reactive oxygen species.

The kinetic characteristics of the interaction of N-acetylcysteine (ASH) with reactive oxygen species (ROS), peroxyl radicals and hydrogen peroxide were determined. It was found that in terms of activity ASH in these reactions is similar to glutathione GSH, the main endogenous bioantioxidant. The kinetics of heat release in the interaction of GSH and ASH with H2O2 was studied for the first time by isothermal calorimetry. It is shown that the kinetic curves of heat release and changes in specific heat release rates practically coincide for both thiols taken in the stoichiometric ratio in the known reaction 2 TSH + H2O2 → TSST + 2 H2O. This indicates the relative autonomy of the S–H and S–S bonds in thiols and disulfides, which are not affected by other groups in the molecule. At pH<7, ASH, like GSH, interacts with H2O2 to form thiyl radicals, which initiate thiol-ene reactions with unsaturated phenol resveratrol. Under the same conditions, ASH ensures nearly the same radical initiation rates as GSH, and thiyl radicals from ASH are close in activity to GS• in chain propagation reactions.

Effect of co-milling on dissolution rate of poorly soluble drugs

Co-milling of a drug with a co-former is an efficient technique to improve the solubility of drugs. Besides the particle size reduction, the co-milling process induces a structural disorder and the creation of amorphous regions. The extent of drug solubility enhancement is dependent on the proper choice of co-milling co-former. The aim of this work was to compare the effects of different co-formers (meglumine and polyvinylpyrrolidone) on the dissolution rates of glass forming (indomethacin) and non-glass forming (mefenamic acid) model drugs. A positive impact of the co-milling on the dissolution behavior was observed in all co-milled mixtures, even if no substantial amorphization was observed. While meglumine exhibited pronounced effects on the dissolution rate of both drugs, the slightest enhancement was observed in mixtures with polyvinylpyrrolidone. The evaluation of specific release rate revealed the surface activation of drug particle is responsible for improving the dissolution rate of both drug types, but for the glass former, this surface activation could be persistent while maintaining a high dissolution rate even until a high fraction of drug is released. Our results, therefore, indicate that adequate co-former choice and consideration of drug glass forming ability are important for a successful co-milling approach to poorly water-soluble drugs.

Long-term effect of graphene oxide on the aerobic granular sludge wastewater treatment process

This study investigated the bioreactor performance, production of extracellular polymeric substance (EPS), and microbial activity of a granulated sequencing batch reactor (SBR) by increasing the graphene oxide nanoparticle (GO NP) concentration stepwise. The GO NPs reduced the removal of chemical oxygen demand (COD), ammonia, and phosphorus, whereas the nitrite and nitrate contents of the effluent were kept stable during the experiment. The ammonia-nitrogen (NH4-N) and COD removal rates were deceased considerably from 99% and 95–96.2% and 78.6% at 55 mg/L GO NPs; furthermore, at 115 mg/L GO NPs, the NH4-N and COD removal rates further decreased to 88.5% and 59.3%. The removal of phosphorus decreased even at small concentrations of graphene oxide (GO), and the inhibitory effect enhanced with an increase in the GO NP content. The increased amounts of nanoparticles significantly influenced the microbial activity of aerobic granular sludge (AGS). The specific oxygen uptake rate (SOUR) decreased from 42.04 to 33.14 mg O2/g MLVSS*h, specific ammonia oxidation rate (SAOR) declined from 4.84 to 4.12 mg N/g MLVSS*h, specific phosphorus uptake rate (SPUR), and specific phosphorus release rate (SPRR) significantly decreased from 13.1 and 10.05–8.2 and 8.7 mg P/g MLVSS*h after 98 days. However, the specific nitrite and nitrate reduction rate (SNIRR and SNRR), and the specific nitrite oxidation rate (SNOR) remained relatively stable. The EPS content of sludge was initially 5.95 mg/g MLVSS, but the presence of GO up a concentration of 55 mg/L promoted the secretion of EPS and increased to 11.86 mg/g MLVSS. At higher GO concentrations, the secretion of EPS was inhibited. After 14 days, when the influent synthetic wastewater (SWW) did not contain GO NP, the AGS SBR performance showed a remarkable recovery capability.

Mutually interacting SNG-air premixed flames

Experimental and numerical studies were conducted to grasp the flame characteristics for mutually interacting SNG-air premixed flames with a counterflow configuration. Five different reaction mechanisms (GRI 3.0, USC 2.0, Aramco 2.0, UCSD, and CRECK) were tested to give the priority in tracing measured lean extinction boundaries. UCSD mechanism best traced the measured data. The flame stability map was presented with a functional dependency on methane mole fractions in the reactant streams issuing from the lower and upper nozzles, by varying the global strain rate.With increasing global strain rate, lean and rich extinction boundaries were gradually slanted, forming an island of flammable region and finally only one flammable condition at 740 s−1 via a continuous shrinkage of flammable region. For asymmetric lean-lean and rich-rich flames, the weaker flame was survived via thermally and chemically symbiotic relation of it to the stronger flame. For lean-rich flames, triple flame is changed into bi-brachial flames via a merging of diffusion flame lean flame at high strain rates. This behavior could be explained well by introducing a specific heat release rate. Extinction mechanism could be reasonably explained by the relation of specific heat release rate (as a reactivity of flame) to conductive heat loss from the strong flame to unburned mixture.

Poly(caprolactone)-Based Coatings on 3D-Printed Biodegradable Implants: A Novel Strategy to Prolong Delivery of Hydrophilic Drugs.

Implantable devices are versatile and promising drug delivery systems, and their advantages are well established. Of these advantages, long-acting drug delivery is perhaps the most valuable. Hydrophilic compounds are particularly difficult to deliver for prolonged times. This work investigates the use of poly(caprolactone) (PCL)-based implant coatings as a novel strategy to prolong the delivery of hydrophilic compounds from implantable devices that have been prepared by additive manufacturing (AM). Hollow implants were prepared from poly(lactic acid) (PLA) and poly(vinyl alcohol) (PVA) using fused filament fabrication (FFF) AM and subsequently coated in a PCL-based coating. Coatings were prepared by solution-casting mixtures of differing molecular weights of PCL and poly(ethylene glycol) (PEG). Increasing the proportion of low-molecular-weight PCL up to 60% in the formulations decreased the crystallinity by over 20%, melting temperature by over 4 °C, and water contact angle by over 40°, resulting in an increased degradation rate when compared to pure high-molecular-weight PCL. Addition of 30% PEG to the formulation increased the porosity of the formulation by over 50% when compared to an equivalent PCL-only formulation. These implants demonstrated in vitro release rates for hydrophilic model compounds (methylene blue and ibuprofen sodium) ranging from 0.01 to 34.09 mg/day, depending on the drug used. The versatility of the devices produced in this work and the range of release rates achievable show great potential. Implants could be specifically developed in order to match the specific release rate required for a number of drugs for a wide range of conditions.

Microwave direct denitration for synthesis of Cu-Ce-Zr-O composite oxide and its characterization

A Cu-Ce-Zr-O composite oxide was synthesized by microwave direct denitration (MDD) and citric acid (CA) methods, with the latter used as an experimental control. X-ray diffraction analysis confirmed that MDD facilitated the formation of a highly homogeneous Cu-Ce-Zr-O composite oxide. The specific surface area and oxygen release rate of the MDD product were 2.2–2.4 and 1.4–1.7 times larger than those of the CA product, respectively, whereas the oxygen storage capacity of the former product was slightly lower than that of the latter. Consequently, it was concluded that MDD did not significantly improve catalytic performance, although it reduced synthesis time and simplified the synthesis process.

Kinetic effects of n-propylbenzene on n-dodecane counterflow nonpremixed cool flames

The development of alternative drop-in fuels and fuel blends with petroleum-derived fuels necessitate an understanding of the kinetic interactions between aromatics and alkanes for the development of advanced low-temperature combustion engines. In the present study, the role of aromatic chemistry on n-alkane low-temperature chemistry is investigated by using nitrogen-diluted nonpremixed cool flames of n-dodecane/n-propylbenzene blends in an atmospheric counterflow burner. Effects of aromatic addition on n-alkane reactivity are examined by fixing the concentration of n-dodecane while varying the ratio of nitrogen/n-propylbenzene. The cool flame structure is probed using formaldehyde laser-induced fluorescence and thermocouple thermometry, and measurements of the cool flame and hot flame extinction limits are obtained. Fundamental differences between the response of cool flame and hot flame heat release and radical production to stretch are also discussed. The results show that, while the specific heat release rate characterizes the burning intensity of a hot flame, the same is not true for a cool flame due to the competition between reactant leakage and negative temperature coefficient reactivity. It is also found that, contrary to hot flames, in cool flames the addition of n-propylbenzene promotes n-dodecane cool flame extinction. Kinetic analysis reveals that aromatics act as a sink of hydroxyl and hydroperoxyl radicals in cool flames by forming stable oxygenated aromatics due to the low flame temperatures. As a result, the low-temperature reactivity of n-dodecane is significantly inhibited by the addition of aromatics, even relative to inert substitution. The present experimental results are valuable for comprehensive chemical kinetic model development and validation.

Photocatalytic water splitting of TiO2 nanotubes powders prepared via rapid breakdown anodization sensitized with Pt, Pd and Ni nanoparticles

The present work deals with the generation of H2 through water splitting using titania (TiO2) nanotubes (NTs) prepared via rapid breakdown anodization. The anatase TiO2 NTs sensitized with Pt, Pd and Ni nanoparticles (NPs) to investigate the efficiency of water splitting of these nanocomposites. The Pt, Pd and Ni NPs were loaded over TiO2 NTs through chemical reduction of the respective precursors. The morphology of the TiO2 NTs was observed to be produced as bundles. The metal NPs sensitized TiO2 NTs as spherical deposits. The H2 generation is larger with the addition of metal NPs and moreover lower quantity deposits produced better results. Pt NPs addition was better among the group in terms of H2 generation over the other metals of the same group. The Pt/TiO2 NTs with 5% metal sensitization generated H2 with a specific release rate of 241.8 μmol g−1 min−1.

Laser-driven calorimetry measurements of petroleum and biodiesel fuels

Thermochemical characteristics were determined for several National Institute of Standards and Technology standard-reference-material petroleum and biodiesel fuels, using a novel laser-heating calorimetry technique. Measurements focused on the sample thermal behavior, specific heat release rate, and total specific heat release. The experimental apparatus consists of a copper sphere-shaped reactor mounted within a chamber, along with laser-beam-steering optical components, gas-supply manifold, and a computer-controlled data-acquisition system. At the center of the reactor, liquid sample is injected onto a copper pan substrate that rests and is in contact with a fine-wire thermocouple. A second thermocouple is in contact with the inner reactor sphere surface. The reactor is heated from opposing sides by a continuous-wave, near-infrared laser beam to achieve nearly uniform sample temperature. The change in temperature with time (thermogram) is recorded for both thermocouples, and compared to a baseline thermogram (without liquid in the pan). The thermograms are then processed (using an equation for thermal energy conservation) for the thermochemical information of interest. The results indicated that the energy reaching the pan is dominated by radiative heat transfer processes, while the dominant thermal process for the reactor sphere is the stored (internal) thermal energy within the sphere material. Sufficient laser power is necessary to detect the fuel thermal-related characteristics, and the required power can differ from one fuel to another. With sufficient laser power, one can detect the preferential vaporization of the lighter and heavier fuel fractions. The total specific heat release obtained for the different conventional and biodiesel fuels used in this investigation were similar to the expected values available in the literature.

Plant Growth and Leachate Electrical Conductivity and pH as Influenced by Controlled-release Fertilizer Blends and Coating Technologies

Although controlled-release fertilizers (CRFs) have been used in container-grown ornamental plants for decades, new coating technologies and blends of fertilizers coated for specific release rates are being employed to customize fertility for specific environments and crops. A study was conducted in the transitional climate of Kentucky to determine the nutrient release rates of three controlled-release blends of 8- to 9-month release and growth response of ‘Double Play Pink’ japanese spirea (Spiraea japonica) and ‘Smaragd’ arbovitae (Thuja occidentalis). Fertilizer 1 (16N–3.5P–8.3K–1.8Mg + trace elements) and Fertilizer 2 (18N–3.1P–8.3K–1.8Mg + trace elements) were prototype blends with different experimental polymer coatings. Fertilizer 3 was a blend of 18N–2.2P–6.6K–1.1Ca–1.4Mg–5.8S + trace elements, which combined 100% resin-coated prills with a polymer coating. Fertilizer 4 was commercially available 15N–3.9P–10K–1.3Mg–6S + trace elements. Fertilizer 3 released its nutrients earlier in the 12-week study than the other three fertilizers and resulted in lower shoot dry weight in both species. The new polymer coating technologies show promise for delivering a predicted release rate and are appropriate for container production of these woody shrubs in Kentucky. An interesting side note of this experiment was that leachate pH measurements across treatments averaged 1.2 units lower for arbovitae (6.3) than for japanese spirea (7.5) at week 12. It was assumed that chemical and/or biological reactions at the root/substrate interface in arbovitae moderated pH increases over the study.

External Phosphorus Adsorption and Immobility with the Addition of Ignited Water Purification Sludge

The cumulative adsorption of external phosphorus (P) by water purification sludge after ignition under different addition methods (mix and cover) was investigated along with the adsorption isotherm and the release of internal P after external P adsorption. The cumulative adsorption of external P was 11.496 mg (mix) and 11.042 mg (cover) and these values were higher than those in the control (7.219 mg). The maximum sorption capacity (Smax) increased under the mix and cover and the former (7.795 mg·g-1) was higher than the latter (6.807 mg·g-1). However, the zero equilibrium P concentration (EPC0) in the mix was 0.83 mg·L-1, higher that in the cover (0.64 mg·L-1). The result suggests that the internal P was easily released in the mix method, compared to the cover method. Under anaerobic conditions, the release of the internal P was 0.93 mg in the mix, lower than that in the cover (1.49 mg) and in the control (7.76 mg). In addition, the specific release rate in the cover method was 0.00614 (mean), higher than that (0.00396) in the mix method. Noticeably, these data were lower than those in the control, indicating that the retention of P under the mix method was higher, compared to the cover and the control and it is challenging to evaluate the P retention with EPC0.