Efficacy and field applicability of Burmese grape leaf extract (BGLE) for cadmium removal: An implication of metal removal from natural water

Adsorption Efficiency of Cadmium (II) by Different Alkali-Activated Materials

The objective of this study was to demonstrate the potential utilization of fly ash (FA), wood ash (WA), and metakaolin (MK) in developing new alkali-activated materials (AAMs) for the removal of cadmium ions from waste water. The synthesis of AAMs involved the dissolution of solid precursors, FA, WA, and MK, by a liquid activator (Na2SiO3 and NaOH). In concentrated solutions of the activator, the formation of an aluminosilicate gel structure occurred. DRIFT spectroscopy of the AAMs indicated main vibration bands between 1036 cm-1 and 996 cm-1, corresponding to Si-O-Si/Si-O-Al bands. Shifting vibration bands were seen at 1028 cm-1 to 1021 cm-1, indicating that the Si-O-Si/Si-O-Al bond is elongating, and the bond angle is decreasing. Based on the X-ray diffraction results, alkali-activated samples consist of an amorphous phase and residual mineral phases. The characteristic "hump" of an amorphous phase in the range from 20 to 40° 2θ was observed in FA and in all AWAFA samples. By the XRD patterns of the AAMs obtained by the activation of a solid three-component system, a new crystalline phase, gehlenite, was identified. The efficiency of AAMs in removing cadmium ions from aqueous solutions was tested under various conditions. The highest values of adsorption capacity, 64.76 mg/g (AWAFA6), 67.02 mg/g (AWAFAMK6), and 72.84 mg/g mg/g (AWAMK6), were obtained for materials activated with a 6 M NaOH solution in the alkali activator. The Langmuir adsorption isotherm and pseudo-second kinetic order provided the best fit for all investigated AAMs.

Valorization of grape (Vitis vinifera) leaves for bioactive compounds: novel green extraction technologies and food-pharma applications

Grape leaves, scientifically known as Vitis vinifera, the primary by-product obtained after the processing of grapes, are gathered in enormous amounts and disposed of as agricultural waste. For more sustainable agriculture and better food systems, it is crucial to investigate these byproducts' nutritional values. The primary bioactive compounds present in grape leaves are quercetin, resveratrol, caffeic acid, kaempferol, and gallic acid, which favour pharmacological effects on human health such as antioxidant, anti-inflammatory, anti-obesity, anti-diabetic, and hepatoprotective. Furthermore, grape leaves extract has been used as a functional ingredient for creating both food and non-food products. The aim of the current review is to review the nutritional and phytochemical composition of various varieties of grape leaves, their health-promoting characteristics and their applications. The study also highlights the various extraction techniques including conventional and non-conventional methods for extracting the various bioactive compounds present in grape leaves. Grape leaves bioactives can be extracted using environmentally safe and sustainable processes, which are in line with the rising demand for eco-friendly and healthful products worldwide. These methods are perfectly suited to the changing needs of both customers and industries since they lessen environmental effect, enhance product quality, and offer financial advantages.

Demystifying the decadal shift in the extent of groundwater in the coastal aquifers of Gujarat, India: A case of reduced extent but increased magnitude of seawater intrusion

Catastrophic increase in urbanisation and industrialisation along the coastal region leads to increased stress on groundwater reservoirs worldwide. As a growing economy, India faces extreme water crises due to rising water demand and escalating salinisation, specifically in the coastal districts. Therefore, this study shows the implication of a comprehensive modelling approach to assess the spatiotemporal changes in hydrogeochemical processes in the coastal aquifer of the Surat district. Using a multi-model assessment approach, the present study focuses on the decadal evolution in groundwater quality of the coastal aquifers of Surat, Gujarat. Fifty-one groundwater samples were collected for 2008, 2012, and 2018 to assess the spatio-temporal shift in groundwater quality. Piper diagram revealed a shift of hydrogeochemical facies from Mg2+-HCO3- type to Ca2+-Mg2+-Cl- type, indicating the increased salinisation over a decade. The result suggests that rock-water interaction, seawater intrusion mechanism, and anthropogenic activities (intensive agricultural activities and improper waste management) govern the hydrogeochemical processes in the coastal aquifer. A shift of dominance of carbonate weathering to silicate weathering with the dissolution of calcite, dolomite, and gypsum, changing the hydrogeochemistry, was observed over the last decades. This shift leads to the increasing hardness of groundwater. The enrichment of nutrients in groundwater during 2018 (NO3- = 2 to 85 mg. L-1) compared to 2008 (NO3- = 1 to 36 mg.L-1) indicates the increasing imprints of agricultural fertilizer application and human organic waste through sewage contamination on the coastal aquifer. The seawater mixing index model demonstrates that extent of seawater intrusion reduced in 2018 compared to 2012, but the magnitude increased near the coastal talukas (SMI =9.5). The present study helps to understand the increasing anthropogenic activities over a decade leading to increased salinisation and groundwater contamination in the aquifer system. This work can help local stakeholders, water resource managers, and the state government manage the groundwater resources and the future potential threat of aquifer contamination.

Aminoalkyl-organo-silane treated sand for the adsorptive removal of arsenic from the groundwater: Immobilizing the mobilized geogenic contaminants

Arsenic (As), a geogenic legacy pollutant can be present in environmental matrices (water, soil, plants, or animal) in two redox states (As(III) or As(V)). In the present study, charged mono- and di-amino functionalized triethoxy and methoxyorganosilane (TT1 and TT2- 1% and 5%) were impregnated with quartz sand particles for the treatment of As polluted water. Spectroscopic characterization of organosilane treated sand (STS) indicated the co-existence of minerals (Mg, Mn, Ti), amide, and amidoalkyl groups, which implies the suitability of silanized materials as a metal(loids) immobilization agent from water. Changes in peaks were observed after As sorption in Fourier thermal infrared and EDS images indicating the involvement of chemisorption. Batch sorption studies were performed with the optimized experimental parameters, where an increased removal (>20% for TT2-1% and >60% for TT1-1%) of As was observed with sorbate concentration (50 µg L^-1), temp. (25 ± 2 ºC) and sorbent dosages (of 10 g L^-1) at 120 min contact time. Among the different adsorbent dosages, 10 g L^-1 of both TT1 and TT2 was selected as an optimum dosage (maximum adsorption capacity ≈ 2.91 μg g^-1). The sorption model parameters suggested the possibility of chemisorption, charge/ion-dipole interaction for the removal of arsenate.

Modeling analysis on the effective elimination of toxic pollutant from aquatic environment using pyrolysis assisted palmyra palm male inflorescence

In this study adsorption of Cd(II) ions using the pyrolysis assisted Palmyra palm male inflorescence (PAPMI) was systematically examined. A batch adsorption study was carried out to determine the type of interactions and removal efficiency which is based on the surface property of PAPMI. The diverse parameters which affect the adsorption performance of PAPMI for Cd(II) ion removal were optimized: biosorbent dose - 1.25 g/L, pH - 6.0, temperature - 303 K, initial cadmium ions concentration - 50 mg/L and contact time - 40 min. Pseudo-first order kinetics and Langmuir isotherm models were more suitable to describe the adsorption kinetics and isotherm, respectively. Therefore, modeling studies portrayed the present Cd(II) ions adsorption on PAPMI as monolayer adsorption occurs on the homogeneous surface and follows the physisorption mechanism. The maximum adsorption capacity of the synthesized PAPMI was examined as 233.2 mg/g from the equilibrium isotherm investigation. Based on the calculated thermodynamic parameters (ΔG^o, ΔH^o and ΔS^o) values, the present Cd(II) ions adsorption on PAPMI was explicated as feasible, and exothermic. The outcome proposed that Palmyra palm male inflorescence can be a suitable adsorbent for expulsion of Cd(II) ions from aqueous environment. In the interim, the utilization of pyrolysis assisted is a viable and fast uptake innovation for the removal of heavy metals from water environment.

Cadmium binding characterization and mechanism of a newly isolated strain Cystobasidium oligophagum QN-3

The aim of this study was to screen a strain for the removal of Cd²⁺ from aqueous solution and investigate the characterization and mechanism of the Cd²⁺ binding process. A novel strain of yeast showed high tolerance of cadmium, namely Cystobasidium oligophagum QN-3, was isolated from soils, which could resist 22,000 mg/L and 18,000 mg/L Cd²⁺ on PDA (potato dextrose agar) plate and in PDA liquid medium, respectively. Cd²⁺ binding experiment showed that the strain could remove Cd²⁺ from aqueous solution effectively, the maximum Cd²⁺ removal rate of 84.45% was achieved at initial Cd²⁺ concentration 30 mg/L. Scanning electron microscopy (SEM) analysis revealed that sorption of Cd²⁺ by cells could be associated with changes in the cell surface morphology. Fourier transform-infrared spectroscopy (FTIR) analysis confirmed the important role of the functional groups OH, CO, NH₂ , COO, PO, and CH on the cell surface in the binding of Cd²⁺ . The comparison of the binding ability of different cellular parts indicated a significant role of the cell wall played in the Cd²⁺ binding process. Pretreatment of the cells by boiling or ultrasonication could improve the biosorption capacity of QN-3. In addition, QN-3 exhibited selective and preferential property of binding capacity for other heavy metals, such as Pb²⁺ , Cu²⁺ , Cd²⁺ , Zn²⁺ , and Ni²⁺ . These data suggested the promising use of Cystobasidium oligophagum QN-3 as an effective and friendly biosorbent for cadmium or other heavy metals decontamination in the environment.

Current advancement and future prospect of biosorbents for bioremediation

The increasing use of heavy metals, synthetic dyes and pesticides is a major environmental concern. Wastewaters containing heavy metals and dyes, extensively released from small and large scale industries enter excessively into food chains resulting in mutagenesis, carcinogenicity and serious health impairments in living systems. The arrays of technologies are implemented to date to remediate both inorganic and organic contaminants from wastewaters. Among which, adsorption is the most attractive method as it employs eco-friendly, sustainable and cost-effective biomaterials. Use of bioadsorbents is advantageous over the conventional adsorbents. Clay, chitin, peat, microbial biomass and agricultural wastes are commonly used bioadsorbants. These bioadsorbents are extensively used for elimination of dyes, heavy metals, adsorption of toxic industrial effluents, removal of fertilizers/pesticides, atmospheric pollutants and nuclear waste from the environment. The current review presents state of the art knowledge on various types of biosorbents, their uses, and mechanism of action. Various strategies to enhance the efficiency of bioadsorbents and physicochemical conditions to remediate dyes and heavy metals from waste streams are also incorporated in this review. Use of nano-bioadsorbents in industries to minimize the hazardous effect of solid and liquid waste has also been discussed.

High sensitivity fiber sensor for measurement of Cd2+ concentration in aqueous solution based on reflective Mach-Zehnder interference with temperature calibration

We propose a novel fiber chemical sensing system based on reflective Mach-Zehnder interference with temperature calibration for the measurement of Cd²⁺ in aqueous solution. The sensing system has high measurement sensitivity of Cd²⁺ with an estimated minimum detection limit of 4×10^-7 mol/L at a spectral resolution of 0.02 nm and with long-term stability. The fiber sensing head is prepared by coating a sensing membrane on a fused tapering single-mode fiber. The thiourea group of the sensing membrane has an effective combination effect on Cd²⁺. Disturbance from ambient temperature fluctuation on the measurement of Cd²⁺ concentration can be eliminated with the fiber Bragg grating.

Removal of p-cresol and tylosin from water using a novel composite of alginate, recycled MnO2 and activated carbon

For sustainable production, there is an urgent need to minimize the adverse environmental impacts of swine farming, which is a major contributor of the pollutants p-cresol and tylosin. Novel reactive composite alginate beads (CAB-MOACs) were fabricated by combining alginate with activated carbon (AC) and MnO₂ recovered from spent battery waste and used for efficient removal of p-cresol and tylosin from water. Batch experiments were carried out under varying pH (3-11), temperature (15-50 °C), and agitation speed (50-200 rpm) to understand their effects on removal efficiency. The CAB-MOACs had better removal efficiency for p-cresol and tylosin than alginate beads alone or beads containing only AC or MnO₂. Adsorption to CAB-MOACs followed pseudo-second-order kinetics (R²≥0.98) and Langmuir isotherm models (R²≥0.95). CAB-MOACs showed higher removal efficiency (∼99.9% after 10 h) compared to beads containing only immobilized MnO₂ (60-70%) or AC (94-96%). Regeneration and reuse performance of the CAB-MOACs was excellent through five cycles, although slightly better for p-cresol than tylosin. With low-cost manufacturing and beneficial utilization of hazardous waste such as spent batteries, the newly developed composite beads show potential as an effective adsorbent for treating wastewater effluent containing emerging contaminants like p-cresol and tylosin. Future studies may focus on product refinement and large-scale testing on actual wastewaters.

Delineating the origin of Pb and Cd in the urban dust through elemental and stable isotopic ratio: A study from Hangzhou City, China

Urban dust (UD) is one of the main sinks of heavy metals in urban environments; however, the sources of these heavy metals are quite difficult to identify. A total of 78 UD samples were collected bi-monthly from October 2012 to August 2013, including 13 sites from three functional areas (residential areas, city parks, and main roads) and the Botanic Garden as a control district. The metal ratios and lead isotopic ratios combined with correlation analysis were used to identify the sources of Pb and Cd in the UD samples. In the scatter plot of Cd/Mn vs Pb/Mn, the dust samples could be classified into four groups showing their different sources and characteristics. Lead isotopic composition analysis indicated that coal combustion was the main source of Pb for residential dusts, while automobile exhaust emission for road dusts. Correlation analysis revealed that the abraded paints was a main contribution of Cd in UD, especially those in city parks. The research provides a useful method of combining multiple approaches to identify sources of metal elements in UD.