Changing the rheological and mechanical behavior of pure bitumen is one of the most important reasons of usage of bitumen modifiers. Polyphosphoric acid is newer additive compared to other additives used in the road construction industry. This additive is used to improve the performance behavior of bitumen and improve bitumen rheological properties such as rutting. In this article, the effect of polyphosphoric acid on performance behavior of bitumen and asphalt mixtures with similar mechanical and chemical properties, but with different chemical compositions, is discussed. Various experiments have been conducted in the field of bitumen and asphalt mixture modification with polyphosphoric acid polymer. The results showed that the addition of PPA can improve the high temperature performance and reduce the temperature sensitivity of the modified bitumen, but it has a slight effect on the low temperature performance. According to the results, bitumens modified with polyphosphoric acid have better fatigue resistance compared to bitumens modified with SBS. Modifying bitumen with PPA leads to an increase in softness, a decrease in permeability, and a decrease in temperature sensitivity. The combination of PPA/SBR has the best rutting resistance in the asphalt mixture due to the highest strength and the smallest rut depth.

In this research, the adsorption of phosphoric acid from an aqueous solution was investigated at different temperatures (298, 308, and 318 K) by using different adsorbents such as wheat bran and banana peels, in a batch system. FTIR and SEM analysis were used, in order to determine the functional groups in the structure of adsorbents and the surface characteristics of adsorbents, respectively. In the adsorption experiments, the effect of important parameters such as the effect of contact time, the amount of adsorbent temperature, and initial acid concentration was investigated. Equilibrium time was determined 40 and 50 minutes for wheat barn and banana peels. The highest percentage of adsorption for banana peel and wheat peel was measured at 71% and 59.8% for 1 g /L phosphoric acid, respectively. The optimum amount of adsorbent was determined 3g. Investigation of the temperature demonstrated that the percentage of removing phosphoric acid decreased by increasing the temperature. Different models of adsorption isotherms such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich models were applied to analyze the equilibrium data at different temperatures and Langmuir and Temkin isotherm have the most agreement with experimental data for absorbents. Different kinetic models such as pseudo-first order, pseudo-second order, Elovich, and intra-particle diffusion model were chosen to describe the kinetic of adsorption, and the pseudo-second-order model for wheat barn and Elovich for banana peels have the best agreement with experimental data for each adsorbent. Thermodynamic parameters like standard Gibbs free energy changes of adsorption (ΔG oads), standard enthalpy changes of adsorption (ΔH oads), and standard entropy changes of adsorption (ΔS oads) were calculated by using equilibrium constant values at different temperatures. The negative value of (ΔG oads) demonstrated that adsorption of phosphoric acid by adsorbents is a spontaneity process and negative values of (ΔH oads) showed that adsorption of phosphoric acid on adsorbents is exothermic. The absorption capacity of banana peel and wheat bran was achieved20 and 11 mg/g, respectively. As a result, banana peel was the appropriate absorbent in this work.

Facilitated transport kinetics of uranium (VI) from a phosphoric acid medium into another phosphoric acid medium as a receiving phase through a bulk liquid membrane containing di-2-ethylhexyl phosphoric acid (HDEPA) as a carrier was studied. The influence of phosphoric acid concentration in source and receiving phases, carrier concentration, type of solvent, stirring speed and temperature were investigated. The kinetic parameters (ke, ks, tmax, Jmax) were calculated for the interfacial reactions, assuming two consecutive, irreversible first-order reactions. The activation energy values were calculated as 29.40 and 19.51 kJmol-1 for extraction and stripping, respectively. The values of the calculated activation energy indicated that the extraction process was controlled by the mixed regime (both kinetic and diffusion), and the stripping process was merely diffusionally controlled. In comparison with HDEPA optimized conditions, though with adding trioctyl-phosphine oxide into membrane phase as a synergic agent, the extraction rate remained approximately constant but the stripping rate diminished dramatically that led to the decrease of the transport kinetics.

One of the most common methods to enhance performance of asphalt binder and mixtures is using polymeric and mineral additives. The polyphosphoric acid (PPA) is one of additives used to modify asphalt binder's characteristics during last two decades. In this research, to investigate the effect of this additive on fracture and crack propagation characteristics of asphalt mixtures, asphalt mixture specimens were fabricated by implementing with asphalt binder modified with three different dosages of PPA: 0.5, 1 and 1.5% by weight of asphalt binder. The semi-circular bending (SCB) test was performed on these specimens at five different test temperatures including -10, 0, 10, 25 and 40 degree of centigrade. The major output of this test was force-displacement curve. The Maximum force, fragility, fracture energy and toughness were determined for all specimens based on force-displacement curve. Also, notch mouth opening displacement was measured by using pictures captured during the SCB test. To compare asphalt mixture behavior, an index was presented in this research as fracture energy divided by noth mouth opening displacement. At a constant temperature, the greater index shows better performance of asphalt mixture. The results have shown that adding PPA at low temperatures is not useful but at moderate temperatures it can increase fracture properties of asphalt mixture. The optimum content of PPA at the moderate temperatures is determined between 0.5 to 1%.

The present research seeks to investigate the modification of bitumen emulsion with polyphosphoric acid and study the feasibility of using steel slag powder as an alternative to conventional rock material filler in the design of microsurfacing mixture in an attempt to improve the ultimate performance of the mixture. For this purpose, firstly, polyphosphoric acid was used to modify the bitumen emulsion at 0.4, 0.8, 1.2, and 1.6 wt% (by weight of residual bitumen). Next, the optimally modified bitumen emulsion was used in different microsurfacing mixtures. Five different mixtures of micro surfacing containing steel slag filler at 0, 2.5, 5.0, 7.5, and 10.0 wt% (by total weight of aggregates), as an alternative to material passing through 0.075 mm sieve, were prepared. The asphalt mixtures were assessed by means of wet cohesion test, wet track abrasion test, loaded wheel-displacement, and loaded wheel-sand adhesion tests. Results of the bitumen tests showed that the use of the polyphosphoric acid tends to improve the bitumen properties in terms of decreased penetration, increased softening point, and reduced thermal sensitivity. With increasing the dosage of the polyphosphoric acid to up to 0.8 wt% by weight of the residual bitumen, significant changes were seen in the penetration and the softening point, which led to improved performance of the bitumen emulsion. Results of the asphalt tests on the samples showed that the mixtures containing steel slag filler at 7.5 and 10.0 wt% outperformed the other mixtures. Indeed, the mixture containing steel slag at 7.5 wt% could improve the cohesion, abrasion resistance, bleeding resistance, and vertical displace resistance by 29.2, 64.5, 18.6, and 44.0%, respectively. The corresponding figures for the mixture containing the slag at 10.0 wt% were 25.0, 64.3, 23.3, and 42.9 wt%, respectively.

Kinetics and mechanism of thorium (IV) transport through a bulk liquid membrane containing di(-2-ethylhexyl) phosphoric acid in kerosene were investigated. The type and concentration of acid in donor and acceptor phases, initial concentration of thorium in donor phase, carrier concentration, and contact time were studied. The optimum transport of thorium were obtained with 0.0001 M HCl in donor phase, 1.5 M H2SO4 in acceptor phase, 0.2 M D2EHPA in kerosene, 50 mg L-1 of thorium in donor phases, and contact time of order of 960 min. The kinetics of thorium (IV) transport were investigated assuming a consecutive, irreversible extraction and back-extraction reactions. The activation energy values of extraction and back-extraction reactions were calculated to be 29.94 kJ mol-1 and 20.55 kJ mol-1, respectively,which indicates that the extraction process was controlled by the mixed regime (both kinetic and diffusion), and the back-extraction process was mainly controlled by diffusion process.

Bis (2-ethylhexyl) phosphoric acid is one of the acid and surfactant compounds that are a useful range of industrial product. Pure Bis (2-ethylhexyl) phosphoric acid compound is common used in hydrometallurgy. In this study, through a stiff reaction of Phosphorous pentoxide and 2-ethylhexanol we prepared a mixture of mono- and bis (2-ethylhexyl) phosphoric acid compounds with a partial phosphoric acid. Because of special structure of the anhydride phosphoric and base on different reaction temperatures and molar ratios of reactants, variety proportions of mono- and diester with small amount of triester and free alcohol were achieved. Equal proportions of mono and diester with 1 to 3 molar proportions of phosphor pentaoxide and 2-ethylhexanol were prepared at 70 ºc and 7 hr. Such results suggest that ratio of mono- and di ester is due to a reaction conditions like time, molar ratio and temperature. In this research high percentage of bis (2-ethylhexyl) phosphoric acid compound is obtained that after purification and separation it was characterized by FT-IR, 1HNMR and 31P-NMR.

Using Ethylene Bis(Stearamide) (EBS) decreases mixing and compaction temperature of bitumen and consequently decreases energy consumption of asphalt mixture production. In this study, polyphosphoric acid (PPA) is added to EBS-modified bitumen to mitigate low-temperature deteriora-tion of EBS. Also, the effect of adding PPA and EBS on high-temperature behavior of bitumen is investigated using supepave protocol and multiple stress creep and recovery (MSCR) test. For this purpose, PPA is added to EBS-modified bitumen (having 3% of EBS) in three different dosages of 0.5, 1, and 1.5% (based on the original bitumen weight). Then, using a dynamic shear rheometer, both superpave protocol test and the MSCR test are performed on all samples at high temperatures. Also, using a bending beam rheometer, the low-temperature behavior of all samples are evaluated. The results showed that while adding 0.5% of PPA did not change mixing and compaction tempera-ture of EBS-modified bitumen significantly, it can improve high-temperature behavior of bitumen. However, MSCR results showed that it is required to consider the high-temperature behavior of modified bitumen conservatively as the bitumen modified with 0.5% PPA and 3% EBS cannot meet standard requirement for three traffic categories.