Adsorptive removal of Cr(VI) and Cu(II) ions from water solution using graphene oxide-manganese ferrite (GMF) nanomaterials

Chromium (Cr) and copper (Cu) are heavy metals known for their dangerous effect towards human health and could enter into human body mainly through ingestion. Over the years, different treatment methods have been used to eliminate heavy metal from raw water source and these include (co)precipitation, coagulation/flocculation, adsorption and ion-exchange. Nonetheless, adsorption is the most prominent method due to its high adsorption capacity and low cost. In this work, graphene oxide-manganese ferrite (GMF) nanomaterials were synthesized and used to remove Cr(VI) and Cu(II) ions from water solution based on adsorption mechanism. The synthesized nanomaterials were characterized using FTIR, BET and TEM prior to use in adsorption process. Batch adsorption studies were carried out to study the adsorption capacity and kinetic properties of the nanomaterials in eliminating two selective heavy metal ions. At optimum pH value, the maximum adsorption capacity for Cr(VI) and Cu(II) are 34.02 and 66.94 mg/g, respectively. The experimental data revealed that the adsorption isotherm best fitted Langmuir model and followed Pseudo second order

Waste reutilization in polymeric membrane fabrication: a new direction in membranes for separation

In parallel to the rapid growth in economic and social activities, there has been an unde-sirable increase in environmental degradation due to the massively produced and disposed waste. The need to manage waste in a more innovative manner has become an urgent matter. In response to the call for circular economy, some solid wastes can offer plenty of opportunities to be reutilized as raw materials for the fabrication of functional, high-value products. In the context of solid waste-derived polymeric membrane development, this strategy can pave a way to reduce the consumption of conventional feedstock for the production of synthetic polymers and simultaneously to dampen the negative environmental impacts resulting from the improper management of these solid wastes. The review aims to offer a platform for overviewing the potentials of reutilizing solid waste in liquid separation membrane fabrication by covering the important aspects, including waste pretreatment and raw material extraction, membrane fabrication and characterizations, as well as the separation performance evaluation of the resultant membranes. Three major types of waste-derived polymeric raw materials, namely keratin, cellulose, and plastics, are discussed based on the waste origins, limitations in the waste processing, and their conversion into polymeric membranes. With the promising material properties and viability of processing facilities, recycling and reutilization of waste resources for membrane fabrication are deemed to be a promising strategy that can bring about huge benefits in multiple ways, especially to make a step closer to sustainable and green membrane production

Effect of hydrophobicity degree on PVDF hollow fiber membranes for textile wastewater treatment using direct contact membrane distillation

The objectives of this study are to study the effect of hydrophobicity degree of polyvinylidene fluoride (PVDF) hollow fiber membranes blended with different types of additives i.e. ethylene glycol (EG) and polyvinylpyrrolidone (PVP) on textile wastewater application. The degree of hydrophobicity of each membrane was analyzed using contact angle goniometer. The membrane morphology and gas permeability were characterized prior to filtration experiment. Both membranes were tested using direct contact membrane distillation (DCMD) system and their performances were evaluated with respect to water flux and dye removal. This study revealed that the membrane with higher contact angle has greater stability in terms of flux and dye rejection compared to the membrane with low hydrophobic property. This is mainly due to the low surface energy obtained by the highly hydrophobic membrane that prevented the liquids from both sides to penetrate through membrane pore

The state-of-the-art development of biochar based photocatalyst for removal of various organic pollutants in wastewater

The use of biochar (BC) as a substrate and dopant in developing composite biochar-based photocatalysts (BBP) has proven to be highly promising in advancing wastewater treatment technology. This review focuses on the development of BBP using agricultural and poultry waste-derived BC to mitigate organic pollutants in water, with emphasis on the synthesis technique employed for the preparation of various BBP. Various techniques for preparing BC and BBP, along with its features and physico-chemical properties, are discussed in detail. The review then delves into the role of BC in influencing the inherent properties of the BBP, particularly in reducing band gap, acting as an electron sink or reservoir, increasing surface active regions, and improving charge separation. Furthermore, the review outlines the synergistic improvement brought about by BC in BBP, specifically in terms of the photodegradation of different classes of pollutants, i.e. pharmaceutical waste, dye from the textile industry, and phenolic compounds. Lastly, the crucial challenges associated with the practical employment of BBP in real-time applications, such as scaling up, long-term stability, and retrofitting into existing wastewater remediation technologies are elaborated. This review will provide significant insights for readers evaluating the sources of BC used as substrates and the methods employed to develop efficient BBP for the remediation of various organic pollutants

Recent progress of Ag/TiO2 photocatalyst for wastewater treatment: Doping, co-doping, and green materials functionalization

Surface modification via doping or functionalization is one of the most commonly applied approaches for addressing the innate limitations of TiO2 photocatalysts. Amongst numerous dopants, silver (Ag) has been regarded as an efficient strategy to retard electron holes recombination due to the formation of the Schottky barrier on the TiO2 interface and extending absorption to the visible region. This review primarily focuses on discussing and evaluating the recent progress in the modification of Ag/TiO2 via co-doping with non-metals and transition metals, as well as the synthesis strategies that have been applied in engineering the materials. The effects of doping and co-doping on the induced chemical and physical properties, photocatalytic performance, stability, and recyclability aspects have also been highlighted. This review also examines the potential improvement of Ag/TiO2 through the addition of green materials such as plant-based materials (cellulose-derived composites, chitosan, alginate), ceramic materials (clay, kaolin bentonite), and also ionic liquid green solvent. Recommendations for further research opportunities, limitations, and challenges have also been suggested

Recent progress of Ag/TiO2 photocatalyst for wastewater treatment: Doping, co-doping, and green materials functionalization

Surface modification via doping or functionalization is one of the most commonly applied approaches for addressing the innate limitations of TiO2 photocatalysts. Amongst numerous dopants, silver (Ag) has been regarded as an efficient strategy to retard electron holes recombination due to the formation of the Schottky barrier on the TiO2 interface and extending absorption to the visible region. This review primarily focuses on discussing and evaluating the recent progress in the modification of Ag/TiO2 via co-doping with non-metals and transition metals, as well as the synthesis strategies that have been applied in engineering the materials. The effects of doping and co-doping on the induced chemical and physical properties, photocatalytic performance, stability, and recyclability aspects have also been highlighted. This review also examines the potential improvement of Ag/TiO2 through the addition of green materials such as plant-based materials (cellulose-derived composites, chitosan, alginate), ceramic materials (clay, kaolin bentonite), and also ionic liquid green solvent. Recommendations for further research opportunities, limitations, and challenges have also been suggested

Visible Light-Driven Organic Pollutant Removal Using Fe-Based Photocatalysts Supported by Wheat Straw Biochar

Researchers are actively pursuing the development of highly functional photocatalyst materials using environmentally friendly and sustainable resources. In this study, wheat straw biochar (BC), a by-product of biomass pyrolysis, was explored as a green, porous substrate and a carbon-based sensitizer to activate Fe-based photocatalysts under visible light. The research also delved into the impact of doping copper (Cu), chromium (Cr), and zinc (Zn) to enhance the photocatalytic activity of BC-Fe-based catalysts for the removal of methylene orange (MO) from water. Characterization results revealed a more than twofold increase in surface area and greater porosity, contributing to improved radical generation. BC demonstrated its dual functionality as a high surface area substrate and an electron sink, facilitating multistep electron movement and enhancing the photoactivity of the composite catalyst. Photodegradation experiments indicated that the combination of BC with Fe and Zn exhibited the highest performance, removing over 80% of MO within 120 min. Parametric studies highlighted the preference for an alkali pH, and the photocatalyst demonstrated efficient performance up to 30 ppm of dye. Radical scavenging experiments identified •OH and h+ as the most generated radicals. This study establishes that the green and sustainable BC holds promise as a material in the quest for more sustainable photocatalysts

Recent progresses of forward osmosis membranes formulation and design for wastewater treatment

Production of potable water or reclaimed water with higher quality are in demand to address water scarcity issues as well as to meet the expectation of stringent water quality standards. Forward osmosis (FO) provides a highly promising platform for energy-efficient membrane-based separation technology. This emerging technology has been recognized as a potential and costcompetitive alternative for many conventional wastewater treatment technologies. Motivated by its advantages over existing wastewater treatment technologies, the interest of applying FO technology for wastewater treatment has increased significantly in recent years. This article focuses on the recent developments and innovations in FO for wastewater treatment. An overview of the potential of FO in various wastewater treatment application will be first presented. The contemporary strategies used in membrane designs and fabrications as well as the efforts made to address membrane fouling are comprehensively reviewed. Finally, the challenges and future outlook of FO for wastewater treatment are highlighted

Recent progress and challenges in hollow fiber membranes for wastewater treatment and resource recovery

Membrane processes have been extensively employed in diverse applications, specifically in industrial wastewater treatment. The technological development in membrane processes has rapidly advanced and accelerated beyond its common principle and operation. Tremendous efforts have been made in the advancement of membrane materials, fabrication method, membrane modification and integration with other technologies that can augment the existing membrane processes to another level. This review presents the recent development of hollow fiber membranes applied in wastewater treatment and resource recovery. The membrane working principles and treatment mechanism were discussed thoroughly, with the recent development of these hollow fiber membranes highlighted based on several types of membrane application. The current challenges and limitations which may hinder this technology from expanding were critically described to offer a better perspective for this technology to be adopted in various potential applications

Recent progress and challenges in hollow fiber membranes for wastewater treatment and resource recovery

Membrane processes have been extensively employed in diverse applications, specifically in industrial wastewater treatment. The technological development in membrane processes has rapidly advanced and accelerated beyond its common principle and operation. Tremendous efforts have been made in the advancement of membrane materials, fabrication method, membrane modification and integration with other technologies that can augment the existing membrane processes to another level. This review presents the recent development of hollow fiber membranes applied in wastewater treatment and resource recovery. The membrane working principles and treatment mechanism were discussed thoroughly, with the recent development of these hollow fiber membranes highlighted based on several types of membrane application. The current challenges and limitations which may hinder this technology from expanding were critically described to offer a better perspective for this technology to be adopted in various potential applications