In this study, the functionalized smectitic clay (SC)-based nanoscale hydrated zirconium oxide (ZrO-SC) was successfully synthesized and utilized for the adsorptive removal of levofloxacin (LVN) from ...an aqueous medium. The synthesized ZrO-SC and its precursors (SC and hydrated zirconium oxide (ZrO(OH)2)) were extensively characterized using various analytical methods to get insight into their physicochemical properties. The results of stability investigation confirmed that ZrO-SC composite is chemically stable in strongly acidic medium. The surface measurements revealed that ZrO impregnation to SC resulted in an increased surface area (six-fold higher than SC). The maximum sorption capacity of ZrO-SC for LVN was 356.98 and 68.87 mg g−1 during batch and continuous flow mode studies, respectively. The mechanistic studies of LVN sorption onto ZrO-SC revealed that various sorption mechanisms, such as interlayer complexation, π-π interaction, electrostatic interaction, and surface complexation were involved. The kinetic studies of ZrO-SC in the continuous-flow mode indicated the better applicability of Thomas model. However, the good fitting of Clark model suggested the multi-layer sorption of LVN. The cost estimation of the studied sorbents was also assessed. The obtained results indicate that ZrO-SC is capable of removing LVN and other emergent pollutants from water at a reasonable cost.
Display omitted
•ZrO(OH)2 nanoparticles were successfully impregnated into the smectitic clay.•The synthesized ZrO-SC exhibits excellent stability in strongly acidic medium.•The ZrO-SC surface area increased more than six-fold after ZrO impregnation.•Complete mechanistic study of LVN sorption by ZrO-SC was successfully provided.•Cost estimation and economic evaluation of SC and ZrO-SC were precisely presented.
Display omitted
•The functionalized biochar-clay composite (FBKC) was successfully synthesized.•FBKC exhibited specific surface area of 221.04 m2/g compared to 47.02 m2/g for BC.•Synergistic sorption ...mechanisms were confirmed for NFX and CVD sorption by FBKC.•FBKC showed a maximum column bed capacity of 37.90 (NFX) and 53.98 mg/g (CVD).•The cost estimation of FBKC was precisely presented, indicating a rate of 5.72 €/kg.
This study investigated the successful synthesis of functionalized algal biochar-clay composite (FBKC). Subsequently, the sorption performance of FBKC towards norfloxacin (NFX) antibiotic and crystal violet dye (CVD) from water was extensively assessed in both batch and continuous flow systems. A series of characterization techniques were carried out for FBKC and the utilized precursors, indicating that the surface area of FBKC was increased thirty-fold with a well-developed pore structure compared to the original precursors. FBKC demonstrated a maximum sorption capacity of 192.80 and 281.24 mg/g for NFX and CVD, respectively. The suited fitting of the experimental data to Freundlich and Clark models suggested multi-layer sorption of NFX/CVD molecules. The mechanistic studies of NFX/CVD sorption onto FBKC unveiled multiple mechanisms, including π-π interaction, hydrogen bonding, electrostatic attraction, and surface/pore filling effect. The estimated cost of 5.72 €/kg and superior sorption capacity makes FBKC an efficient low-cost sorbent for emergent water pollutants.
Oxidase and peroxidase enzymes have attracted attention in various biotechnological industries due to their ease of synthesis, wide range of applications, and operation under mild conditions. Their ...applicability, however, is limited by their poor stability in harsher conditions and their non-reusability. As a result, several approaches such as enzyme engineering, medium engineering, and enzyme immobilization have been used to improve the enzyme properties. Several materials have been used as supports for these enzymes to increase their stability and reusability. This review focusses on the immobilization of oxidase and peroxidase enzymes on metal and metal oxide nanoparticle-polymer composite supports and the different methods used to achieve the immobilization. The application of the enzyme-metal/metal oxide-polymer biocatalysts in biosensing of hydrogen peroxide, glucose, pesticides, and herbicides as well as blood components such as cholesterol, urea, dopamine, and xanthine have been extensively reviewed. The application of the biocatalysts in wastewater treatment through degradation of dyes, pesticides, and other organic compounds has also been discussed.
The discharge of cosmetic wastewater into the wastewater treatment systems has become an environmental concern due to high concentrations of nutrients. The current study explored the phytoremediation ...potential of Desmodesmus multivariabilis, under mixotrophic growth, to remove total organic carbon (TOC), sulfur (TS), nitrogen (TN), and phosphorus (TP) from cosmetic wastewater (CWW). The CWW was prepared using samples supplied by a local cosmetic production company (two dyes, two hair relaxers, as well as two shampoos and conditioners). The bioremediation potential of D. multivariabilis was tested under four different conditions: raw CWW with 0% CO2 in the aeration stream (i.e., atmospheric air); pre-treated CWW with 0% CO2, 2.5% CO2, and 5% CO2. Control experiments were run in parallel. Under mixotrophic growth, the microalga performed best at 5% CO2 in the pre-treated CWW where TOC, TN, TP, and TS removal of >88%, >98%, >95%, and >90% were measured, respectively. The corresponding biomass (dry weight) was >203 mg/L. Relaxers promoted growth most prominently; however, it was observed that there was significant nutrient removal even in the absence of growth in all experiments. The growth followed Liebig’s Law, displaying three distinct phases (CO2 concentration, CO2 mass transfer, and nutrient limited growth). The results demonstrated the potential for the successful bioremediation of cosmetic wastewater by D. multivariabilis.
Phosphate rock, pre-concentrated phosphate ore, is the primary raw material for the production of mineral phosphate fertilizer. Phosphate rock is among the fifth most mined materials on earth, and it ...is also mined and processed to fertilizers in East Africa. Phosphate ore can contain relevant heavy metal impurities such as toxic cadmium and radiotoxic uranium. Prolonged use of phosphate rock powder as a fertilizer and application of mineral fertilizers derived from phosphate rock on agricultural soils can lead to an accumulation of heavy metals that can then pose an environmental risk. This work assesses the uranium concentrations in four major phosphate rocks originating from East Africa and four mineral phosphate fertilizers commonly used in the region. The concentration measurements were performed using energy-dispersive X-ray fluorescence spectrometry. The results showed that the uranium concentration in phosphate rock ranged from as low as 10.7 mg kg
−1
(Mrima Hill deposit, Kenya) to as high as 631.6 mg kg
−1
(Matongo deposit, Burundi), while the concentrations in phosphate fertilizers ranged from 107.9 for an imported fertilizer to 281.0 mg kg
−1
for a local fertilizer produced from Minjingu phosphate rock in Tanzania. In this context, it is noteworthy that the naturally occurring concentration of uranium in the earth crust is between 1.4 and 2.7 mg kg
−1
and uranium mines in Namibia commercially process ores with uranium concentrations as low as 100–400 mg kg
−1
. This study thus confirms that East African phosphate rock, and as a result the phosphate fertilizer produced from it can contain relatively high uranium concentrations. Options to recover this uranium are discussed, and it is recommended that public–private partnerships are established that could develop economically competitive technologies to recover uranium during phosphate rock processing at the deposits with the highest uranium concentrations.
Renewable biowaste-derived carbon dots have garnered immense interest owing to their exceptional optical, fluorescence, chemical, and environmentally friendly attributes, which have been exploited ...for the detection of metals, non-metals, and organics in the environment. In the present study, water-soluble fluorescent carbon dots (CDs) were synthesized via facile green microwave pyrolysis of pine-cone biomass as precursors, without any chemical additives. The synthesized fluorescent pine-cone carbon dots (PC-CDs) were spherical in shape with a bimodal particle-size distribution (average diameters of 15.2 nm and 42.1 nm) and a broad absorption band of between 280 and 350 nm, attributed to a π-π* and n-π* transition. The synthesized PC-CDs exhibited the highest fluorescent (FL) intensity at an excitation wavelength of 360 nm, with maximum emission of 430 nm. The synthesized PC-CDs were an excellent fluorescent probe for the selective detection of Cu2+ in aqueous solution, amidst the presence of other metal ions. The FL intensity of PC-CDs was exceptionally quenched in the presence of Cu2+ ions, with a low detection limit of 0.005 μg/mL; this was largely ascribed to Cu2+ ion binding interactions with the enriched surface functional groups on the PC-CDs. As-synthesized PC-CDs are an excellent, cost effective, and sensitive probe for detecting and monitoring Cu2+ metal ions in wastewater.
Three brands of NPK fertilizers that contain variable concentrations of natural radioactivity are commonly used in tobacco plantations in Kenya, Tanzania, and Uganda. Tobacco plants are known for ...hyper-accumulation of natural radionuclides, particularly
238
U. This study investigated if the elevated radioactivity in phosphate fertilizers could enhance radioactivity in soils and tobacco plant leaves. The
232
Th,
238
U, and
40
K radionuclide levels in NPK-fertilized soils and tobacco leaves were measured using gamma-ray spectroscopy. The research included a one-year reference experiment with tobacco growing in plots, a ten-year semi-controlled experiment in well-managed tobacco farms, and a field survey of radioactivity in soils and tobacco leaves at three traditional tobacco fields in Migori (Kenya), Urambo (Tanzania), and Kanungu (Uganda). The findings demonstrated that soils and tobacco leaves exposed to NPK fertilizers with increased radioactivity had activity concentrations of
232
Th,
238
U, and
40
K that were considerably higher (at all sites) than in the control samples (with no use of NPK fertilizers). As the continued application of NPK fertilizers raises concentrations of
232
Th,
238
U, and
40
K in agricultural soils, the study assessed radiological risks for humans from exposure to agricultural soils enriched with phosphate fertilizers, and it was found to be below the exposure limit of 1 mSvy
-1
suggested by the International Commission on Radiological Protection (ICRP). However, tobacco consumers, both by snuffing and smoking, may face significant radiological risks, as the snuffing and smoking resulted in effective doses that were 2.41 to 6.53 and 1.14 to 2.45 times greater than the average yearly dose that the general public receives from inhalation of natural radionuclides (United Nations Scientific Committee on Atomic Radiations estimates). Furthermore, the results indicate that the lifetime excess cancer risk for tobacco snuffers and smokers ranged from 5 × 10
-5
to 24.48 × 10
-3
and 2.0 × 10
-5
to 9.18 × 10
-3
, respectively. The influence of phosphorus-derived fertilizer containing relatively high natural radioactivity, potential human radiation exposure, and radiological risk due to gamma radionuclides is estimated and discussed. The results reveal that applying phosphate fertilizers enhances natural radioactivity in soil and is subsequently influenced by soil to tobacco plant uptake. Therefore, the study recommends that countries use fertilizers with lower radionuclide content to conserve soil quality and reduce gamma-emitting radionuclides in tobacco plants.
The continuous increase of urbanization and industrialization brought various climatic changes, leading to global warming. The unavailability of meteorological data makes remotely sensed data ...important for understanding climate change. Therefore, the land surface temperature (LST) is critical in understanding global climate changes and related hydrological processes. The main objective of this work is to explore the dominant drivers of land use and hydrologic indices for LST in drainage and non-drainage areas. Specifically, the relationship between LST changes, land use, and hydrologic indices in Northeast Qena, Egypt, was investigated. The Landsat 5 and 8 imagery, Geographic Information System (GIS), and R-package were applied to identify the change detection during 2000–2021. The normalized difference between vegetation index (NDVI), bare soil index (BSI), normalized difference built-up, built-up index (BUI), modified normalized difference water index (MNDWI), and soil-adjusted vegetation index (SAVI) were employed. The non-drainage or mountain areas were found to be more susceptible to high LST values. The comprehensive analysis and assessment of the spatiotemporal changes of LST indicated that land use and hydrologic indices were driving factors for LST changes. Considerably, LST retrieved from the Landsat imaginary showed significant variation between the maximum LST during 2000 (44.82°C) and 2021 (50.74°C). However, NDBI has got less spread during the past (2000) with 10–13%. A high negative correlation was observed between the LST and NDVI, while the SAVI and LST positively correlated. The results of this study provide relevant information for environmental planning to local management authorities.
Display omitted
•Significant temporal variation in LST (2000–2021) was extensively investigated.•Increasing LST trend from 2000 (44.82 °C) to 2021 (50.74 °C) was detected.•Climate change impact was strongly proved in the studied area.•LST analysis and indices support UN-SDGs and climate action.
The Philippines produce some 2.1–3.2 million t phosphogypsum (PG) per year. PG can contain elevated concentrations of rare earth elements (REEs). In this work, the leaching efficiency of the REEs ...from Philippine PG with H
2
SO
4
was for the first time studied. A total of 18 experimental setups (repeated 3 times each) were conducted to optimize the acid concentration (1–10%), leaching temperature (40–80 °C), leaching time (5–120 min), and solid-to-liquid ratio (1:10–1:2) with the overall goal of maximizing the REE leaching efficiency. Applying different optimizations (Taguchi method, regression analysis and artificial neural network (ANN) analysis), a total REEs leaching efficiency of 71% (La 75%, Ce 72%, Nd 71% and Y 63%) was realized. Our results show the importance of the explanatory variables in the order of acid concentration > temperature > time > solid-to-liquid ratio. Based on the regression models, the REE leaching efficiencies are directly related to the linear combination of acid concentration, temperature, and time. Meanwhile, the ANN recognized the relevance of the solid-to-liquid ratio in the leaching process with an overall
R
of 0.97379. The proposed ANN model can be used to predict REE leaching efficiencies from PG with reasonable accuracy.
Phosphogypsum (PG) accumulates during wet-phosphoric acid production for fertilizers. In the Philippines, PG is partly (40%) utilized to produce gypsum walls and cement. This work assesses the ...radiological risks and resource opportunities associated with PG stacks in the Philippines. The conducted in situ radiometric survey measured the activity concentrations of
40
K,
238
U, and
232
Th at 270 locations. Besides, another 120 surface samples were collected. Pure PG exceeds the recommended radiation limits, but simple dilution with conventional materials can make PG available as an inexpensive secondary raw material for construction. PG further contains relevant concentrations of rare earths and Y (195 ppm).
PDF