Applicability of TiO2(B) nanosheets@hydrochar composites for adsorption of tetracycline (TC) from contaminated water

We test the feasibility of TiO2(B)@carbon composites as adsorbents, derived from wheat straws, for tetracycline (TC) adsorption from aqueous solutions. Hydrochar (HC), biochar (BC), and hydrochar-derived pyrolysis char (HDPC) are synthesized hydrothermally from the waste and then functionalized with TiO2(B), named as ‘Composite-1′ , ‘Composite-2′ , and ‘Composite-3′ , respectively. A higher loading of TiO2(B) into the HC was also synthesized for comparison, named as ‘Composite-4′ . To compare their physico-chemical changes before and after surface modification, the composites are characterized using FESEM-EDS, XRD, BET, FRTEM, and FTIR. The effects of H2O2 addition on TC removal are investigated. Adsorption kinetics and isotherms of TC removal are studied, while TC adsorption mechanisms are elaborated. We found that the Composite-4 has the highest TC removal (93%) at pH 7, 1 g/L of dose, and 4 h of reaction time at 50 mg/L of TC after adding H2O2 (10 mM). The TC adsorption capacities of the Composite-1 and Composite-4 are 40.65 and 49.26 mg/g, respectively. The TC removal by the Composite-1 follows the pseudo-second order. Overall, this suggests that converting the wheat straw into HC and then functionalizing its surface with TiO2(B) as a composite has added values to the waste as an adsorbent for wastewater treatment

Promoting sustainable cleaner production paradigms in palm oil fuel ash as an eco-friendly cementitious material: A critical analysis

Long term goals need to be set to promote the country's circular economy (CE) as well as the cleaner environment by recycling waste materials into useful products. In pursuit of controlling environmental threats of carbon-based industrial wastes, different preprocessing techniques for their conversion into other value-added materials are being put in use. This review targets the purposeful utilization of massive amount of palm oil fuel ash (POFA), generated as a waste from power plants of palm oil processing mills in the major palm oil-producing countries. Currently, unrestrained disposal of POFA captures not only precious land but also creates environmental threats and health-related issues. Present work is an attempt to establish a sustainable cleaner production (SCP) system instead of unmanaged POFA disposal. Major palm oil producer countries should address the emerging issues of POFA related unsafe environment, energy consumption and landfill spaces by adopting reuse, reduce and recycle principles. Technically, this review also focuses on the use of POFA as a promising cementitious material in concrete production. It also maps the importance of POFA in concrete production as a cement replacement by presenting various state-of-the-art chemical reactions, mode of action of POFA for its pozzolanic reactivity in cement compositions and associated technical, environmental, and economic benefits. This will provide an alternative option and a sustainable solution for the global construction industry. It is conclusively evident from an extensive literature survey of 463 published results from last 26 years that POFA can be effectively used in concrete production to replace cement without compromising on its strength, performance, and durability. Based on the till that research work on POFA applications in the cement industry and other multiple areas, a circular economic model has been presented to support the concept of zero waste and SCP. It will stimulate the technical persons and decision-makers to make policies and strategies that can spotlight the effective use of POFA in multiple applications, primarily focusing on concrete production not only for curtailing the land and water pollution but also acquiring economic benefits

Structural, optical, and photocatalytic investigation of nickel oxide@graphene oxide nanocomposite thin films by RF magnetron sputtering

Despite the recent advancement in graphene oxide (GO) as a host material in energy and environmental sectors, its composite thin films with metal oxides such as nickel oxide (NiO) and its optical, structural, chemical state, and photocatalytic activities have been poorly explored. Herein, we have reported the GO/NiO thin films preparation by a combination of chemical and physical deposition techniques (i.e. spin coating followed by DC/RF sputtering). The as-prepared composites thin films were characterised using Raman spectroscopy, X-ray diffraction/photoelectron spectroscopy scanning electron microscopy, and atomic force microscopy. The surface topography confirmed the uniform deposition of NiO over thin films of GO. The XPS results showed the formation of NiC along with the partial reduction in GO into graphene with their existing four constituents, i.e. NiO, NiC, GO, in the thin film composites. The classical plasmon, Wemple and Didomenico model, was first time applied for GO/NiO to compute energy loss functions, and dispersion energy parameters. The theoretical calculated values for the deposited GO/NiO thin films were found to be in very close agreement to the standard classical plasmon values. The change in spin orbital movement of Ni is considered due to the interaction between its nanoparticles and basal planes of GO. Thin films applied for the photodegradation of recalcitrant organic pollutant 2-chlorophenol (2-CP) revealed the dependence of photocatalytic efficiency on particle size and also on the interaction of GO with NiO rather than the ratio of NiO and GO in the films

Development of high strength, porous mullite ceramic hollow fiber membrane for treatment of oily wastewater

Ceramic hollow fiber membranes (CHFMs) are known for their excellent characteristics including high surface area, compact design, and good chemical, thermal, and mechanical stabilities. Despite these interesting attributes, CHFMs are also prone to certain limitations, such as brittleness and high cost that hinder them from being commercialized. To mitigate this drawback, we have developed a high strength, porous ceramic hollow fiber membrane, derived from mullite–kaolinite powder, for efficient oil–wastewater separation. The superhydrophilic, low-cost mullite-based (CHFM) was successfully fabricated through combined phase inversion and sintering techniques. Prior to the fabrication, the as-received mullite–kaolinite was characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and Brunauer–Emmett–Teller (BET) analyses. Subsequently, operational parameters such as the effect of mullite content, sintering temperature, and air gap were optimized during the fabrication of mullite ceramic hollow fiber membrane. The resulting membranes were systematically characterized and evaluated in terms of morphology, porosity, mechanical strength, water flux, and oil–water separation. Increasing the mullite content, air gap, and sintering temperature enhanced the formation of microvoid structure. It is interesting to note that the mechanical strength of 86 MPa was obtained for the membrane containing 60 wt % of mullite sintered at 1450 °C and an air gap of 5 cm. The membrane induced a stable permeate water flux and oil rejection of mullite CHFM of 182 L/m2·h and 97.1%, respectively. As compared to kaolin ceramic counterparts, this porous mullite ceramic hollow fiber membrane can be used in various water treatment applications, including for the separation of oily wastewater due to its mechanical strength and water flux

Assessment of Sewage Molecular Markers: Linear Alkylbenzenes in Sediments of an Industrialized Region in Peninsular Malaysia

In this study, the use of linear alkylbenzenes (LABs) was employed to pinpoint the sources of human activity that cause detrimental impacts on the coastal environment and river ecosystems. LABs were detected using GC–MS in sediment samples assembled from Kim Kim River (KKR) and the Port Dickson coast (PDC). To assess the significance of variations in the distribution and concentrations of LABs across the sampling sites, this study utilized several statistical techniques such as post hoc tests, LSD techniques, analysis of variance (ANOVA), and the Pearson correlation coefficient using a significance level of p 13 and C12, and long-to-short-chain (L/S) ratios. The results revealed that the LAB concentrations varied between 88.3 and 112 ng/g dw in KKR and 119 to 256 ng/g dw in the PDC. Most of the surveyed areas exhibited a substantial count of C13–LABs homologs that displayed a significant difference (p < 0.05). The I/E ratios ranged from 1.7 to 2.0 in KKR and from 2.0 to 4.1 in the PDC, suggesting that the effluents originated from sources associated with the physical phase and biological phase in wastewater treatment systems (WWTSs). The results revealed that the degradation of LABs varied between 34% and 38% in KKR and between 40% and 64% in the PDC. This study underscores the importance of ongoing improvements to WWTSs and emphasizes the potential of LABs as indicators for monitoring wastewater contamination

Arsenic adsorption mechanism on palm oil fuel ash (POFA) powder suspension

The contribution of palm oil fuel ash (POFA), an agricultural waste as a low cost adsorbent for the removal of arsenite (As(III)) and arsenate (As(V)) was explored. Investigation on the adsorbency characteristics of POFA suspension revealed that the surface area, particle size, composition, and crystallinity of the SiO2 rich mullite structure were the crucial factors in ensuring a high adsorption capacity of the ions. Maximum adsorption capacities of As(III) and As(V) at 91.2 and 99.4 mg g−1, respectively, were obtained when POFA of 30 μm particle size was employed at pH 3 with the highest calcination temperature at 1150 °C. An optimum dosage of 1.0 g of dried POFA powder successfully removed 48.7% and 50.2% of As(III) and As(V), respectively. Molecular modeling using the density functional theory consequently identified the energy for the proposed reaction routes between the SiO− and As+ species. The high stability of the POFA suspension in water in conjunction with good adsorption capacity of As(III) and As(V) seen in this study, thus envisages its feasibility as a potential alternative absorbent for the remediation of water polluted with heavy metals

Ammonia removal by adsorptive clinoptilolite ceramic membrane: Effect of dosage, isothermal behavior and regeneration process

This work investigates the effectiveness of ammoniacal nitrogen (NH4+-N) removal from contaminated water by adsorptive hollow fiber ceramic membrane (HFCM) derived from naturally made clinoptilolite. The technological value of this work is the simple mechanism of the adsorptive HFCM in removing gaseous ammonia in water by combining adsorption and separation. To test the technical feasibility of this proposed technology, clinoptilolite HFCM was fabricated via phase inversion-based extrusion/sintering technique and characterized by SEM and water permeation flux. The produced HFCM corresponds to the desired morphology of the asymmetric structure (dense and void formations) with outstanding adsorption performance of NH4+-N. The effects of the HFCM’s operational parameters on its removal are examined in terms of membrane dosage and isothermal studies. The adsorption isotherm behavior exhibited that the adsorption process fitted the Freundlich isotherm model with outstanding removal performance even at trace concentration of ammonia. The low amount used by HFCM (4.75×10-4 m2) resulted in over 96% ammonia removal, indicating a low cost of adsorption process. The regeneration of saturated HFCM suggests an outstanding recovery of the HFCM for its subsequent use for NH4+-N removal. This study also reveals the potential of adsorptive HFCM as a simple and cost-effective technology for ammonia removal from wastewater

Bisphenol A Removal Using Visible Light Driven Cu₂O/PVDF Photocatalytic Dual Layer Hollow Fiber Membrane

Bisphenol A (BPA) is amongst the endocrine disrupting compounds (EDCs) that cause illness to humans and in this work was removed using copper (I) oxide (Cu2O) visible light photocatalyst which has a narrow bandgap of 2.2 eV. This was done by embedding Cu2O into polyvinylidene fluoride (PVDF) membranes to generate a Cu2O/PVDF dual layer hollow fiber (DLHF) membrane using a co-extrusion technique. The initial ratio of 0.25 Cu2O/PVDF was used to study variation of the outer dope extrusion flowrate for 3 mL/min, 6 mL/min and 9 mL/min. Subsequently, the best flowrate was used to vary Cu2O/PVDF for 0.25, 0.50 and 0.75 with fixed outer dope extrusion flowrate. Under visible light irradiation, 10 mg/L of BPA was used to assess the membranes performance. The results show that the outer and inner layers of the membrane have finger-like structures, whereas the intermediate section of the membrane has a sponge-like structure. With high porosity up to 63.13%, the membrane is hydrophilic and exhibited high flux up to 13,891 L/m2h. The optimum photocatalytic membrane configuration is 0.50 Cu2O/PVDF DLHF membrane with 6 mL/min outer dope flowrate, which was able to remove 75% of 10 ppm BPA under visible light irradiation without copper leaching into the water sample

Low Nickel, Ceria Zirconia-Based Micro-Tubular Solid Oxide Fuel Cell: A Study of Composition and Oxidation Using Hydrogen and Methane Fuel

The study examines the effect of using low nickel (Ni) with high ceria (CeO2) anode content towards the oxidation of H2 and CH4 fuel by evaluating the activation energy of the ohmic process and charge transfer process. Using a micro-tubular solid oxide fuel cell (MT-SOFC), the anodes are made up of 50% YSZ with varying NiO:CeO2 percentages from 0% NiO, 50% CeO2 to 50% NiO, 0% CeO2. The performance is measured based on maximum power density (MPD), electrochemical impedance spectroscopy (EIS) and activation energy, Ea of the ohmic (Rohm) and charge transfer (Rct) processes. We found that by lowering the Ni content to lower than 50% NiO, anode conductivity will drop by 7-fold. An anode containing 37.5% NiO, 12.5% CeO2 yield MPD of 41.1 and 2.9 mW cm−2 when tested on H2 and CH4 fuels thus have the lowest Ni content without an abrupt negative effect on the MPD and EIS. The significant effect of conductivity drops on MPD and EIS are observed to occur at 25% NiO, 25% CeO2 and lower NiO content. However, anode content of 25% NiO, 25% CeO2 has the lowest Ea for Rct (29.74 kJ mol−1) for operation in CH4, making it the best anode composition to oxidize CH4. As a conclusion, an anode containing 25% NiO:25% CeO2:50% YSZ and 37.5% NiO:12.5% CeO2:50% YSZ shows promising results in becoming the low Ni anode for coking-tolerant SOFC