Physical, leaching, and toxicity characteristics of PG76 binder modified with Rediset

Asphalt binder, as one of pavement component is exposed to heat and rainfall. Polymer modified asphalt binder is a good alternative to withstand the weather in tropical countries. By utilizing warm mix asphalt additive, the high compacting and mixing temperature can be reduced. However, the impact to the environment and its characteristic towards high temperature need to be evaluated before putting it to use. In the study, the physical properties, thermal characteristics, and leaching and toxicity of PG76 incorporated with Rediset LQ were investigated. The Tank Leaching Test was carried out to mimic the worst scenario of flood event effect on the asphalt binder. The results of physical tests denote that the new material has relative consistency while the thermal analysis indicates that the materials are stable beyond their mixing and compaction temperature. The decomposition starts at temperature > 360°C and ends at temperature <500°C for all samples. The tank leaching test also found that the materials are safe to be used as pavement material because the heavy metal elements from the leachate are below the maximum allowable volume by the World Health Organization and the United States Environmental Protection Agency.

Efficient chemical stabilization of tannery wastewater pollutants in a single step process: Geopolymerization

The treatment of tannery wastewaters is a complex task due to the complexity of the waste: a mixture of several pollutants, both anionic and cationic as well as organic macromolecules which are very hard to treat for disposal all together. Geopolymers are a class of inorganic binders obtained by alkali activation of aluminosilicate powders at room temperature. Such activation process leads to a cement like matrix that drastically decreases mobility of several components via entrapment. This process taking place in the matrix can be hypothesized to be the in-situ formation of zeolite structures. In this work we use a metakaolin based geopolymer to tackle the problem directly in an actual industrial environment. To obtain a geopolymer, the metakaolin was mixed with 10 wt% of wastewater added with sodium hydroxide and sodium silicate as activating solutions. This process allowed a rapid consolidation at room temperature, the average compressive strength was between 14 and 43 MPa. Leaching tests performed at different aging times confirm a high immobilization efficiency close to 100%. In particular, only the 0.008 and 2.31% of Chromium and Chlorides respectively are released in the leaching test after 7 months of aging.

Effect of Fly Ash on Leaching Characteristics of Cement-Stabilized Macadam Base

To study the leaching characteristics of a cement-stabilized macadam base with fly ash, a calcium leaching test, using varying cement and fly ash dosages in an ammonium chloride solution, was designed to obtain the rate of calcium ion leaching, porosity, and permeability coefficient of cement-stabilized macadam with leaching time. The results showed that the number of leached calcium ions increased with the cement dosage in the leaching of cement-stabilized macadam. With an increase in the cement dosage, the leaching rate of calcium ions decreased, and the leaching process of the material was delayed. The incorporation of fly ash could effectively slow down the degree of calcium ion leaching. The permeability coefficient increased gradually with the extension of leaching time, and the increase in fly ash content had a more significant effect on the improvement of the permeability coefficient than the increase in cement dosage did.

Vinasse-Based Slow-Release Organo-Mineral Fertilizer with Chitosan-Bentonite Matrix

Controlling the release rate of the nitrogen-phosphorus-potassium (NPK) for the soil fertilized can enhance the fertilizer efficiency and reduce the drawback for the environmental. In this work, a novel slow-release organo-mineral fertilizer was produced from the vinasse, which was blended with the NPK and the chitosan-bentonite matrix. The NPK used as additional nutrients source and the chitosan-bentonite matrix was performed as a barrier to prevent the nitrogen, phosphorus, and potassium from a rapid dissolving. The NPK release rate was measured and analyzed after 3, 6, 9, and 12 days using the incubation method and leaching test. The most efficient release rate was obtained when a dry vinasse mixed with 9% NPK and 5% chitosan-bentonite matrix with the ratio of 8:2. The vinasse-based slow-release of organo-mineral fertilizer (SR-OMF) was compared to the vinasse organo-mineral fertilizer (OMF). The result indicated that the NPK release rate in the vinasse-based SR-OMF was lower compared to that in the vinasse OMF.

Anthropogenic Organic Pollutants in Groundwater Increase Releases of Fe and Mn from Aquifer Sediments: Impacts of Pollution Degree, Mineral Content, and pH

In many aquifers around the world, there exists the issue of abnormal concentrations of Fe and Mn in groundwater. Although it has been recognized that the main source of this issue is the release of Fe and Mn from aquifer sediments into groundwater under natural environmental conditions, there lacks enough reliable scientific evidence to illustrate whether the pollutants imported from anthropogenic activities, such as organics, can increase this natural release. On the basis of time series analysis and comparative analysis, the existence of an increasing effect was verified through laboratorial leaching test, and the impacts of aquatic chemical environment conditions, such as pH, on the effect were also identified. The results showed that the increase of organics in groundwater made the release of Fe and Mn more thorough, which was favorable for the increase of groundwater concentrations of Fe and Mn. The higher the contents of Fe- and Mn-bearing minerals in aquifer sediments, the higher the concentrations of Fe and Mn in groundwater after the release reaches kinetic equilibrium. Lower pH can make the leaching more thorough, but the neutral environment also increases the amount of Mn. It can be deduced that the pollutants such as organics imported by anthropogenic activities can indeed increase the releases of Fe and Mn from aquifer sediments into groundwater, thus worsening the issue of groundwater Fe and Mn pollution. The findings provide a deeper insight into the geochemical effects of Fe and Mn in the natural environment, especially in the groundwater system.

A Method of Improving Physical Adsorption of Cellulase On Mesoporous Zr-Based MOF Surface: Enhanced Stability, Recyclability, And Catalytic Efficiency

In this paper, we aimed at developing immobilized cellulase biocatalyst by enhancing the anchor of cellulase on support surface. A mesoporous Zr-based MOF was first synthesized by biomineralization method using dextran as template. The resultant PVP-cellulase@CD-UIO-66-Zr exhibited a high loading capacity of 265 mg g− 1 support. The physical adsorption of cellulase on CD-UIO-66-Zr could be further enhanced by the capping of cellulase with PVP. About 83% of the activity of PVP-cellulase@CD-UIO-66-Zr could be retained after six cycles, and its equilibrium leakage ratio was 36% during thirty days’ leaching test. It was noting that about 80% of activity of immobilized PVP-cellulase@CD-UIO-66-Zr could be retained after incubation at 80°C for 1 hour. The immobilized cellulase exhibited higher pH stability, thermostability, storage stability and catalytic efficiency than free one.

A Low Cost of Burning Raw Material For PO43−-P And F− Solidification/Stabilization In Phosphogypsum

Phosphogypsum (PG) contains a lot of soluble phosphate (PO4 3−-P) and fluorine ion (F−), which seriously has hindered the sustainable development of phosphorous chemical industry. In this study, a new burning raw material (BRM) was used for the stabilize of PO43−-P and F− in PG. The characteristics of PG and BRM, stabilize mechanism of PO43−-P and F−, leaching test and economic evaluation were investigated. The effect of PG and BRM weight ratio, solid to liquid ratio, reaction time and reaction temperature on the concentrations of PO43−-P and F− were studied. The results showed that the concentration of F− in PG leaching solution was 8.65 mg/L and the removal efficiency of PO43−-P was 99.78 %, as well as the pH of PG leaching solution was 8.12, when the weight ratio of PG and BRM was 100:2, and the solid to liquid ratio was 4:1, reacting for 24 h at the temperature of 30 ℃. PO43−-P and F− were mostly solidified as Ca5(PO4)3F, CaPO3(OH), Ca5(PO4)3(OH), Ca2P2O7·2H2O, CaSO4PO3(OH)·4H2O, CaF2, and CaFPO3·2H2O. Leaching test results indicated that the concentrations of PO4 3−-P, F− and heavy metals were less than the integrated wastewater discharge standard (GB8978-1996). Economic evaluation revealed that the cost of PG treatment was $ 0.88/ton. This study provides a new low cost and harmless treatment method for PG.

Alternative Remediation for Raw Petroleum Sludge by Using Solidification/stabilization Method

In Malaysia, the current practise in treatment of petroleum sludge (PS) is by using incineration and the ash produce required further treatment for safely disposal into landfill. This process require high cost and treatment of raw sludge by using solidification/stabilization method was introduce. In this study, ordinary Portland cement was used as binder. This study focuses on physical properties (compressive strength, density test and water absorption) of S/S matrices and leaching behaviour (SPLP). Results shows adds up to of 30% PS gives results on strength which comply with minimum landfill dispose limit. Correlation between strength and density in regression coefficient of 80.99% and correlation between strength and water absorption shows strong regression of 93.12%. Leaching behaviours on 28 th day of curing showed the similar trend as on 7th day of curing. All heavy metals concentration in leaching test were below the USEPA standard except for Nickel and Chromium. Even though these two metals were exceeded the standard, Portland cement was capable to encapsulate Ni and Cr in mixture and reduce the concentration of 87% and 69% (PS 40%), respectively, compare to concentration in raw sludge. As, conclusion S/S method can be an alternative disposal method for raw sludge.