Pb(II) removal from water using Fe-coated bamboo charcoal with the assistance of microwaves

Quantification adsorption mechanisms of arsenic by goethite-modified biochar in aqueous solution

In this study, rice straw biochar (BC), goethite (GT), and goethite-modified biochar (GBC) were prepared and their differences in adsorption characteristics and mechanisms of arsenic were explored to provide theoretical and data reference for future design of modified biochar, aiming to address adsorption mechanism weakness and improve the efficiency of arsenic removal in water. Various characterization methods were employed to evaluate the influence of pH, adsorption kinetics, isotherms, and chemical analyses of the materials. At temperatures of 283 K, 298 K, and 313 K, the maximum actual adsorption capacity followed the order GBC > GT > BC, while at 313 K, the maximum Langmuir adsorption capacity of GBC reached 149.63 mg/g which was 95.92 times that of BC and 6.27 times of GT. Due to precipitation and complexation mechanisms, GBC exhibited more superior arsenic adsorption capacities than BC and GT, contributing to total adsorption ranging from 88.9% to 94.2%. BC was dominated by complexation and ion exchange mechanisms in arsenic adsorption, with contribution proportions of 71.8%-77.6% and 19.1%-21.9%, respectively. In GT, the precipitation mechanism played a significant role in total adsorption, contributing from 78.0% to 84.7%. Although GBC has significant potential for removing arsenic from aqueous solutions, the findings suggest that its ion exchange capacity needs improvement.

Industrial byproducts for the soil stabilization of trace elements and per- and polyfluorinated alkyl substances (PFASs)

The present work was the first exploration of the use of industrial byproducts from iron and titanium processing as sorbents for the stabilization of soil contamination. The main aim was to test slag waste and iron-rich charred fossil coal ("Fe-char"), as sorbents for per- and polyfluorinated alkyl substances (PFASs), as well as lead (Pb) and antimony (Sb), in four soils from a firefighting training area (PFASs) and a shooting range (Pb and Sb). Adding slag (10-20%) to shooting range soils decreased the leaching of Pb and Sb up to 50-90%. Fe-char amendment to these soils resulted in a moderate reduction in Sb leaching (20-70%) and a slightly stronger effect on Pb (40-50%). The sorption is most likely explained by the presence of Fe oxyhydroxides. These are present in the highest concentrations in the slag, probably resulting in more effective metal binding to the slag than to the Fe-char. Fe-char but not slag proved to be a strong sorbent for PFASs (reducing PFAS leaching from the soil by up to 99.7%) in soil containing low total organic carbon (TOC; 1.2%) but not in high-TOC soil (34%). The sorption coefficient K_D for Fe-char was high, in the range of 10^4.3 to 10^6.5 L/kg at 1 ng/L in the low-TOC soil. The K_D value increased with increasing perfluorocarbon chain length, exceeding PFAS sorption to biochar in the low ng/L concentration range. This result indicates that the mechanism behind the strong PFAS sorption to Fe-char was mainly van der Waals dispersive interactions between the hydrophobic PFAS-chain and the aromatic π-electron systems on nanopore walls within the Fe-char matrix. Overall, this study indicates that industrial byproducts can provide sustainable and cost-effective materials for soil remediation. However, the sorbent needs to be tailored to the type of soil and type of contamination.

Magnetic Adsorbents for Wastewater Treatment: Advancements in Their Synthesis Methods

The remediation of water streams, polluted by various substances, is important for realizing a sustainable future. Magnetic adsorbents are promising materials for wastewater treatment. Although numerous techniques have been developed for the preparation of magnetic adsorbents, with effective adsorption performance, reviews that focus on the synthesis methods of magnetic adsorbents for wastewater treatment and their material structures have not been reported. In this review, advancements in the synthesis methods of magnetic adsorbents for the removal of substances from water streams has been comprehensively summarized and discussed. Generally, the synthesis methods are categorized into five groups, as follows: direct use of magnetic particles as adsorbents, attachment of pre-prepared adsorbents and pre-prepared magnetic particles, synthesis of magnetic particles on pre-prepared adsorbents, synthesis of adsorbents on preprepared magnetic particles, and co-synthesis of adsorbents and magnetic particles. The main improvements in the advanced methods involved making the conventional synthesis a less energy intensive, more efficient, and simpler process, while maintaining or increasing the adsorption performance. The key challenges, such as the enhancement of the adsorption performance of materials and the design of sophisticated material structures, are discussed as well.

Acid Soils Nitrogen Leaching and Buffering Capacity Mitigation Using Charcoal and Sago Bark Ash

Soil acidity compromises agricultural output in tropical acid soils. Highly weathered tropical acidic soils are characterized by low pH, organic matter, nutrient availability, but high aluminium and iron concentration. Hence, N availability becomes a limiting factor in such soils. To this end, these leaching and pH buffering capacity studies were conducted to determine the effects of co-application of charcoal and sago bark ash on the N leaching or retention and pH buffering capacity of acid soils. The soil leaching experiment was conducted for 30 days by spraying distilled water to each container with soil such that the leachates were collected for analysis. The rate of urea used was fixed at 100% of the recommended rate. The rates of charcoal and sago bark ash were varied by 25%, 50%, 75%, and 100%, respectively, of the recommended rates. The pH buffering capacity was calculated as the negative reciprocal of the slope of the linear regression. The leaching study revealed that the combined use of charcoal, sago bark ash, and urea does not only reduce leaching of NH4+ and NO3− but the approach also improves soil pH, total C, and soil exchangeable NH4+. This effect is related to the fact that the sago bark ash deprotonates the functional groups of charcoal because of its neutralizing components such as Ca, Mg, Na, and K ions. As a result, the combined use of charcoal and sago bark ash was able to retain NH4+ in the soil. The carbonates in the sago bark ash and functional groups of charcoal improve pH buffering capacity. Thus, the combined use of charcoal and sago bark ash improved soil exchangeable NH4+, soil pH, and soil total C, but reduced exchangeable acidity and amount of NH4+ leached out from soil. This study will be further evaluated in a pot trial to confirm the results of the present findings.

Assisted phytostabilization of Pb-spiked soils amended with charcoal and banana compost and vegetated with Ricinus communis L. (Castor bean)

A greenhouse experiment was performed to elucidate the potency of Prosopis juliflora charcoal (PJC) and banana waste compost (BWC) to improve soil fertility and enhance plant growth rate. Plantlets of Ricinus communis were grown in 0, 400, and 800 mg kg^-1 Pb-spiked soil ameliorated with P. juliflora charcoal and banana waste compost at 0, 5%, and 10% (w/w) for 60 days. PJC and BWC significantly (p < 0.05) increased plant growth parameters, that is, number of leaves, node number, plant height, and leaf diameter and reduced oxidative stress manifested by the lesser production of proline, hydrogen peroxide (H₂O₂), and malondialdehyde (MDA) with respect to control plants. Soil usage of PJC at 10% decreased the Pb accumulation by 61%, whereas BWC decreased Pb concentration in roots by 56% concerning control. Field emission scanning electron microscope (FE-SEM) coupled with energy-dispersive X-ray spectroscopy (EDS) showed high macro and microspores on the surface of charcoal while banana compost showed significant raise in the nutrient content (N, P, K, Zn, Ca, Fe, and Mg). Thermogravimetric (TG) and Fourier-transform infrared spectroscopy (FTIR) analysis of banana compost showed enhanced molar convolution of carbohydrate composites and nitrogen content. These findings pave a clear understanding that PJC and BWC are recalcitrant for Pb phytotoxicity and can also be used as nutrient-rich composites for increased crop production.

The effects of different factors on the removal mechanism of Pb(ii) by biochar-supported carbon nanotube composites

Herein, biochar-supported nanomaterials were synthesized using a mixture of chestnut shells and carbon nanotubes via slow pyrolysis at 600 °C for 1 h. Then, the adsorption ability of chestnut shell-carbon nanotubes (CS-CNTs) towards the removal of aqueous Pb(ii) was tested. The removal capacity of Pb(ii) by CS-CNT was 1641 mg g⁻¹, which was significantly higher than that by the biochar of chestnut shells (CSs) (1568 mg g⁻¹), which demonstrated that the sorption capacity could be improved by the carbon nanotubes. The factors studied here indicated that the adsorption was rapid in the initial 15 min under the conditions of the Pb(ii) concentration of 50 mg L⁻¹ and the pH value of 5, and the values reached 1417 mg g⁻¹ and 1584 mg g⁻¹. The adsorption rate and capacity increased on increasing the concentration of NaCl. The sorption reaction was consistent with the Langmuir model, indicating a mono-layer adsorption behavior. The adsorption process can also be defined via the pseudo-second-order model, suggesting that the adsorption of Pb(ii) might be controlled by chemisorption. After carrying out four cycles of adsorption–desorption experiments, the adsorption rates of CS and CS-CNT remained at 82.92% and 88.91%, respectively, indicating that the biochar samples had stable and excellent sorption ability for heavy metals and huge application value. Thus, this study would provide a promising sorbent for the treatment and remediation of metal contaminants.

In this study, biochar and biochar-supported nanocomposites were prepared through the slow pyrolysis of chestnut shells pre-treated with CNTs, and the effects of different factors on the sorption of Pb(ii) on biochar samples were investigated.

Fabrication of WO3·2H2O/BC Hybrids by the Radiation Method for Enhanced Performance Supercapacitors

In this study, we described a facile process for the fabrication of tungsten oxide dihydrate/bamboo charcoal hybrids (WO₃·2H₂O/BC) by the γ-irradiation method. The structural, morphological, and electrochemical properties of WO₃·2H₂O/BC hybrids were investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) techniques. The combination of BC (electrical double layer charge) and WO₃·2H₂O (pseudocapacitance) created a combined effect, which enhanced the specific capacitance and superior cyclic stability of the WO₃·2H₂O/BC hybrid electrode. The WO₃·2H₂O/BC hybrids showed the higher specific capacitance (391 F g⁻¹ at 0.5 A g⁻¹ over the voltage range from −1 to 0 V), compared with BC (108 F g⁻¹) in 6 M KOH solution. Furthermore, the hybrid electrode showed superior long-term performance with 82% capacitance retention even after 10,000 cycles. The experimental results demonstrated that the high performance of WO₃·2H₂O/BC hybrids could be a potential electrode material for supercapacitors.

A Novel Radiation Method for Preparing MnO₂/BC Monolith Hybrids with Outstanding Supercapacitance Performance

A novel facile process for fabrication of amorphous MnO₂/bamboo charcoal monolith hybrids (MnO₂/BC) for potential supercapacitor applications using γ-irradiation methods is described. The structural, morphological and electrochemical properties of the MnO₂/BC hybrids have been investigated using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectroscopy (EIS) techniques. The combination of BC (electrical double layer charge) and MnO₂ (pseudocapacitance) created a complementary effect, which enhanced the specific capacitance and good cyclic stability of the MnO₂/BC hybrid electrodes. The MnO₂/BC hybrids showed a higher specific capacitance (449 F g⁻¹ at the constant current density of 0.5 A g⁻¹ over the potential range from –0.2 V to 0.8 V), compared with BC (101 F g⁻¹) in 1 M of Na₂SO₄ aqueous electrolyte. Furthermore, the MnO₂/BC hybrid electrodes showed superior cycling stability with 78% capacitance retention, even after 10,000 cycles. The experimental results demonstrated that the high performance of MnO₂/BC hybrids could be a potential electrode material for supercapacitors.

Engineered/designer biochar for contaminant removal/immobilization from soil and water: Potential and implication of biochar modification

The use of biochar has been suggested as a means of remediating contaminated soil and water. The practical applications of conventional biochar for contaminant immobilization and removal however need further improvements. Hence, recent attention has focused on modification of biochar with novel structures and surface properties in order to improve its remediation efficacy and environmental benefits. Engineered/designer biochars are commonly used terms to indicate application-oriented, outcome-based biochar modification or synthesis. In recent years, biochar modifications involving various methods such as, acid treatment, base treatment, amination, surfactant modification, impregnation of mineral sorbents, steam activation and magnetic modification have been widely studied. This review summarizes and evaluates biochar modification methods, corresponding mechanisms, and their benefits for contaminant management in soil and water. Applicability and performance of modification methods depend on the type of contaminants (i.e., inorganic/organic, anionic/cationic, hydrophilic/hydrophobic, polar/non-polar), environmental conditions, remediation goals, and land use purpose. In general, modification to produce engineered/designer biochar is likely to enhance the sorption capacity of biochar and its potential applications for environmental remediation.

Pollution due to hazardous glass waste

Pollution resulting from hazardous glass (HG) is widespread across the globe, both in terms of quantity and associated health risks. In waste cathode ray tube (CRT) and fluorescent lamp glass, mercury and lead are present as the major pollutants. The current review discusses the issues related to quantity and associated risk from the pollutant present in HG and proposes the chemical, biological, thermal, hybrid, and nanotechniques for its management. The hybrid is one of the upcoming research models involving the compatible combination of two or more techniques for better and efficient remediation. Thermal mercury desorption starts at 100 °C but for efficient removal, the temperature should be >460 °C. Involvement of solar energy for this purpose makes the research more viable and ecofriendly. Nanoparticles such as Fe, Se, Cu, Ni, Zn, Ag, and WS2 alone or with its formulation can immobilize heavy metals present in HG by involving a redox mechanism. Straight-line equation from year-wise sale can provide future sale data in comparison with lifespan which gives future pollutant approximation. Waste compact fluorescent lamps units projected for the year 2015 is 9,300,000,000 units and can emit nearly 9,300 kg of mercury. On the other hand, CRT monitors have been continuously replaced by more improved versions like liquid crystal display and plasma display panel resulting in the production of more waste. Worldwide CRT production was 83,300,000 units in 2002 and can approximately release 83,000 metric tons of lead.

Sedimentary records of PAHs in a sediment core from tidal flat of Haizhou Bay, China

The concentrations and depositional fluxes of polycyclic aromatic hydrocarbons (PAHs) were investigated in a dated sediment core collected from a tidal flat in Haizhou Bay, China. The USEPA's 16 priority PAH concentrations ranged from 72.51 ng g(-1) dw in 1969 to 805.21 ng g(-1) dw in 2010, while the deposition fluxes were in the range of 102.36-861.02 ng cm(-2) yr(-1). The PAH concentrations and fluxes changed dramatically with depth, suggesting changes in energy usage and corresponding closely with the historical economic development of eastern China. The levels of PAHs slightly increased from the late 1970s, following China's "Reform and Open" policy of 1978; however, a drastic increase in the concentration of PAHs observed in 1990 was indicative of the rapid growth in coal and petroleum incomplete combustion byproducts, which was associated with the increase in economic development in this area. Furthermore, isomer ratio analysis and principle component analysis revealed the main anthropogenic pyrolytic source that causes PAH contamination in the coastal sediment.