Khairiraihanna Johari

Bio: Khairiraihanna Johari is an academic researcher from Universiti Teknologi Petronas. The author has contributed to research in topics: Adsorption & Langmuir adsorption model. The author has an hindex of 20, co-authored 61 publications receiving 1101 citations. Previous affiliations of Khairiraihanna Johari include Universiti Teknologi Malaysia.

A critical review on TiO2 based photocatalytic CO2 reduction system: Strategies to improve efficiency

Abstract: The massive burning of fossil fuels to fulfill the augmenting energy demands of world have triggered the ever-increasing emission of carbon dioxide (CO2); the main cause of global warming. Photocatalytic reduction of CO2 into solar fuels and chemicals using everlasting solar energy seems promising technology to contemporaneously curb the globa1 warming and partially fulfill the energy requirements. This study focused on understanding the main challenges in photocatalytic CO2 reduction systems and strategies to improve the efficiency of solar fuels production. The overview of fundamentals and latest developments in titania (TiO2) based photocatalytic CO2 reduction systems have been discussed. More specifically, thermodynamics, mass transfer, selectivity and reaction mechanism of photocatalytic CO2 reduction are critically deliberated. In the main stream, developments have been categorized as strategies to enhance the different aspects such as visible light response, charge separation, CO2 adsorption and morphology of photo-catalysts for TiO2 based photocatalytic CO2 reduction systems. Different modification techniques to overcome the low efficiency by fabricating advance TiO2 nanocomposites through surface modifications, doping of metals, non-metals and semiconductor are discussed. The challenges lingering on against achieving the higher photocatalytic conversion of CO2 into solar fuels are also investigated. In conclusion, brief perspectives and recommendations on the development of efficient photocatalysts are outlined which would be of vital importance for the improvements of conversion efficiency of CO2 reduction system.

Removal of Hg(II) from Aqueous Solution by Adsorption Using Raw and Chemically Modified Rice Straw As Novel Adsorbents

Abstract: A novel mercapto-grafted rice straw (RS-GM) was synthesized and characterized against raw rice straw (RS-Raw). The RS-GM yielded a better Hg(II) biosorption performance compared to RS-Raw as the incorporated-mercaptan functional group presented a strong affinity toward Hg(II). The isotherm data correlated well with the Langmuir isotherm model having maximum biosorption capacity, qmax of 103.10 mg/g and 161.30 mg/g for RS-Raw and RS-GM, respectively. The Hg(II) biosorption is thermodynamically feasible, endothermic, and spontaneous in nature. The biosorption kinetic data were best-fitted into the pseudo-second-order kinetic model. Further analysis suggested that the Hg(II) biosorption process is governed by the intraparticle and external mass transfer in which the film diffusion was the rate limiting step. The adsorption–desorption cycle was repeated four times by using diluted HCI as desorbing agent, and the results were comparable to the unused biosorbent. The removal of Hg(II), which was also done in th...

Cocatalysts for Selective Photoreduction of CO2 into Solar Fuels.

Abstract: Photoreduction of CO2 into sustainable and green solar fuels is generally believed to be an appealing solution to simultaneously overcome both environmental problems and energy crisis. The low selectivity of challenging multi-electron CO2 photoreduction reactions makes it one of the holy grails in heterogeneous photocatalysis. This Review highlights the important roles of cocatalysts in selective photocatalytic CO2 reduction into solar fuels using semiconductor catalysts. A special emphasis in this review is placed on the key role, design considerations and modification strategies of cocatalysts for CO2 photoreduction. Various cocatalysts, such as the biomimetic, metal-based, metal-free, and multifunctional ones, and their selectivity for CO2 photoreduction are summarized and discussed, along with the recent advances in this area. This Review provides useful information for the design of highly selective cocatalysts for photo(electro)reduction and electroreduction of CO2 and complements the existing reviews on various semiconductor photocatalysts.

Efficient techniques for the removal of toxic heavy metals from aquatic environment: A review

Abstract: The controversy related to the environment pollution is increasing in human life and in the eco-system. Especially, the water pollution is growing rapidly due to the wastewater discharge from the industries. The only way to find the new water resource is the reuse of treated wastewater. Several remediation technologies are available which provides a convenience to reuse the reclaimed wastewater. Heavy metals like Zn, Cu, Pb, Ni, Cd, Hg, etc. contributes various environmental problems based on their toxicity. These toxic metals are exposed to human and environment, the accumulation of ions takes place which causes serious health and environmental hazards. Hence, it is a major concern in the environment. Due to this concern, the significance of developing technology for removing heavy metals has been increased. This paper contributes the outline of new literature with two objectives. First, it provides the sketch about treatment technologies followed by their heavy metal capture capacity from industrial effluent. The treatment performance, their remediation capacity and probable environmental and health impacts were deliberated in this review article. Conclusively, this review paper furnishes the information about the important methods incorporated in lab scale studies which are required to identify the feasible and convenient wastewater treatment. Moreover, attempts have been made to confer the emphasis on sequestration of heavy metals from industrial effluent and establish the scientific background for reducing the discharge of heavy metals into the environment.

Unique S-scheme heterojunctions in self-assembled TiO2/CsPbBr3 hybrids for CO2 photoreduction.

Abstract: Exploring photocatalysts to promote CO2 photoreduction into solar fuels is of great significance. We develop TiO2/perovskite (CsPbBr3) S-scheme heterojunctions synthesized by a facile electrostatic-driven self-assembling approach. Density functional theory calculation combined with experimental studies proves the electron transfer from CsPbBr3 quantum dots (QDs) to TiO2, resulting in the construction of internal electric field (IEF) directing from CsPbBr3 to TiO2 upon hybridization. The IEF drives the photoexcited electrons in TiO2 to CsPbBr3 upon light irradiation as revealed by in-situ X-ray photoelectron spectroscopy analysis, suggesting the formation of an S-scheme heterojunction in the TiO2/CsPbBr3 nanohybrids which greatly promotes the separation of electron-hole pairs to foster efficient CO2 photoreduction. The hybrid nanofibers unveil a higher CO2-reduction rate (9.02 μmol g–1 h–1) comparing with pristine TiO2 nanofibers (4.68 μmol g–1 h–1). Isotope (13CO2) tracer results confirm that the reduction products originate from CO2 source. Rational design and fabrication of high-performance photocatalyst is of great importance for CO2 reduction into solar fuel. Here, the authors demonstrate that S-scheme heterojunction TiO2/CsPbBr3 photocatalyst exhibits enhanced CO2 photoreduction activity.

Insight into the adsorption kinetics models for the removal of contaminants from aqueous solutions

Abstract: The past decade has seen a boom in environmental adsorption studies on the adsorptive removal of pollutants from the aqueous phase. A large majority of works treat kinetic modeling as a mere routine to describe the macroscopic trend of adsorptive uptake by using common models, often without careful appraisal of the characteristics and validity of the models. This review compiles common kinetic models and discusses their origins, features, modified versions (if any), and applicability with regard to liquid adsorption modeling for both batch adsorption and dynamic adsorption systems. Indiscriminate applications, ambiguities, and controversies are highlighted and clarified. The appropriateness of linear regression for correlating kinetic data is discussed. This review concludes with a note on the current scenario and the future of kinetics modeling of liquid adsorption.