Photocatalytic systems as an advanced environmental remediation: Recent developments, limitations and new avenues for applications

Ahmad, Rizwan,Ahmad, Zaki,Khan, Asad Ullah,Mastoi, Naila Riaz,Aslam, Muhammad,Kim, Jeonghwan Elsevier 2016 Journal of environmental chemical engineering Vol.4 No.4

<P><B>Abstract</B></P> <P>Heterogeneous photocatalysis is a promising technology especially for environmental remediation. Despite more than a decade of worldwide research in developing photocatalytic efficiency improving techniques, many questions regarding the large scale application of photocatalytic reactors still remain unanswered. Recently, improving the photocatalytic efficiency has gained scientific attention because it might lead to more economical and robust photocatalytic operation for environmental remediation. In this review, fundamental and comprehensive assessments of the photocatalytic concepts and their applications for environmental remediation are reviewed. The existing challenges and strategies to improve the photocatalytic efficiency are discussed. Further, recent developments and future research prospects on photocatalytic systems for environmental applications are also addressed.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Photocatalytic systems for improved environmental remediation. </LI> <LI> Existing challenges and techniques to improve quantum efficiency for environmental remediation. </LI> <LI> Optimization of parameters governing capability of photocatalytic systems. </LI> <LI> Applications of photocatalytic systems in new avenues for environmental remediation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

페닐 스티릴 케톤 수지의 합성과 이들의 수용액상의 납(2)과 구리(2) 이온의 흡착에의 응용

Tashfeen Akhtar,Rizwan N. Paracha,Shahid Hameed,Nasim H. Rama,Masud Riaz 한국고분자학회 2007 폴리머 Vol.31 No.2

Biochar soil amendment on alleviation of drought and salt stress in plants: a critical review

Ali, S.,Rizwan, M.,Qayyum, M. F.,Ok, Y. S.,Ibrahim, M.,Riaz, M.,Arif, M. S.,Hafeez, F.,Al-Wabel, M. I.,Shahzad, A. N. Springer Science + Business Media 2017 Environmental Science and Pollution Research Vol.24 No.14

<P>Drought and salt stress negatively affect soil fertility and plant growth. Application of biochar, carbon-rich material developed from combustion of biomass under no or limited oxygen supply, ameliorates the negative effects of drought and salt stress on plants. The biochar application increased the plant growth, biomass, and yield under either drought and/or salt stress and also increased photosynthesis, nutrient uptake, and modified gas exchange characteristics in drought and salt-stressed plants. Under drought stress, biochar increased the water holding capacity of soil and improved the physical and biological properties of soils. Under salt stress, biochar decreased Na+ uptake, while increased K+ uptake by plants. Biochar-mediated increase in salt tolerance of plants is primarily associated with improvement in soil properties, thus increasing plant water status, reduction of Na+ uptake, increasing uptake of minerals, and regulation of stomatal conductance and phytohormones. This review highlights both the potential of biochar in alleviating drought and salt stress in plants and future prospect of the role of biochar under drought and salt stress in plants.</P>

Strengthening of concrete damaged by mechanical loading and elevated temperature

Ahmad, Hammad,Hameed, Rashid,Riaz, Muhammad Rizwan,Gillani, Asad Ali Techno-Press 2018 Advances in concrete construction Vol.6 No.6

Despite being one of the most abundantly used construction materials because of its exceptional properties, concrete is susceptible to deterioration and damage due to various factors particularly corrosion, improper loading, poor workmanship and design discrepancies, and as a result concrete structures require retrofitting and strengthening. In recent times, Fiber Reinforced Polymer (FRP) composites have substituted the conventional techniques of retrofitting and strengthening of damaged concrete. Most of the research studies related to concrete strengthening using FRP have been performed on undamaged test specimens. This contribution presents the results of an experimental study in which concrete specimens were damaged by mechanical loading and elevated temperature in laboratory prior to application of Carbon Fiber Reinforced Polymer (CFRP) sheets for strengthening. The test specimens prepared using concrete of target compressive strength of 28 MPa at 28 days were subjected to compressive and splitting tensile testing up to failure and the intact pieces of the failed specimens were collected for the purpose of repair. In order to induce damage as a result of elevated temperature, the concrete cylinders were subjected to $400^{\circ}C$ and $800^{\circ}C$ temperature for two hours duration. Concrete cylinders damaged under compressive and split tensile loads were re-cast using concrete and rich cement-sand mortar, respectively and then strengthened using CFRP wrap. Concrete cylinders damaged due to elevated temperature were also strengthened using CFRP wrap. Re-cast and strengthened concrete cylinders were tested in compression and splitting tension. The obtained results revealed that re-casting of specimens damaged by mechanical loadings using concrete & mortar, and then strengthened by single layer CFRP wrap exhibited strength even higher than their original values. In case of specimens damaged by elevated temperature, the results indicated that concrete strength is significantly dropped and strengthening using CFRP wrap made it possible to not only recover the lost strength but also resulted in concrete strength greater than the original value.

Reinforced fibrous recycled aggregate concrete element subjected to uniaxial tensile loading

Hameed, R.,Hasnain, K.,Riaz, M. Rizwan,Khan, Qasim S.,Siddiqi, Zahid A. Techno-Press 2020 Advances in concrete construction Vol.9 No.2

In this study, effect of recycled aggregates and polypropylene fibers on the response of conventionally reinforced concrete element subjected to tensile loading in terms of tension stiffening and strain development was experimentally investigated. For this purpose, concrete prisms of 100 × 100 mm cross section and 500 mm length having one central deformed steel re-bar were cast using fibrous and non-fibrous Recycled Aggregate Concrete (RAC) with varying percentages of recycled aggregates (0%, 25%, 50%, 75% and 100%) and tested under uniaxial tensile load. For all fibrous RAC mixes, polypropylene fibers were used at constant dosage of 3.15 kg/㎥. Effect of recycled aggregates and fibers on the compressive strength of concrete was also explored in this study. Through studying tensile load versus global axial deformation of composite and strain development in concrete and steel, it was found that replacement of natural aggregates with recycled aggregates in concrete negatively affected the cracking load, tension stiffening and strain development, and this negative effect was observed to be increased with increasing contents of recycled aggregates in concrete. The results of this study showed that it was possible to minimize the negative effect of recycled aggregates in concrete by the addition of polypropylene fibers. Reinforced concrete element constructed using concrete containing 50% recycled aggregates and polypropylene fibers exhibited cracking behavior, tension stiffening and strain development response almost similar to that of concrete element constructed using natural aggregate concrete without fiber.

Effect of opposing jet on aerodynamic and flight stability characteristics of a generic supersonic slender forebody

Shagufta Rashid,Fahad Nawaz,Adnan Maqsood,Shuaib Salamat,Rizwan Riaz 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.6

Active flow control techniques, such as opposing jets, hold a high potential to mitigate wave drag effects in supersonic and hypersonic regimes. In literature, most of the work is related to blunt shape bodies and their aerodynamic analysis. This article focuses on using an opposing jet in a drag reduction of a slender forebody and associated changes in flight stability characteristics. Unsteady Reynolds averaged Navier-Stokes (URANS) based solver is used for flow-field modeling. The free-stream flows at a Mach of 1.6 with the jet ejection Mach of 1 is considered. Analysis of the 3D shockwave and its displacement from the surface of the body is discussed. This analysis includes the parametric study of pressure ratios (PR = 3 to 15) with increasing angles of attack ( ∞α = 0° to 4°). The ejection of the jet displaces the shockwave from the leading edge of the slender forebody, which ultimately affects the body’s stability. The longitudinal flight stability characteristic of the body is studied in detail, with and without the jet’s ejection. This study indicates an improvement in the static stability coefficients (C ) at low angles of attack. The dynamic stability coefficients ( +C C ) are also analyzed. It is concluded that the opposing jet improves the stability characteristics of the slender forebody.