Synthesis of green marine algal-based biochar for remediation of arsenic(V) from contaminated waters in batch and column mode of operation

Biochar applications for treating potentially toxic elements (PTEs) contaminated soils and water: a review

Environmental pollution with potentially toxic elements (PTEs) has become one of the critical and pressing issues worldwide. Although these pollutants occur naturally in the environment, their concentrations are continuously increasing, probably as a consequence of anthropic activities. They are very toxic even at very low concentrations and hence cause undesirable ecological impacts. Thus, the cleanup of polluted soils and water has become an obligation to ensure the safe handling of the available natural resources. Several remediation technologies can be followed to attain successful remediation, i.e., chemical, physical, and biological procedures; yet many of these techniques are expensive and/or may have negative impacts on the surroundings. Recycling agricultural wastes still represents the most promising economical, safe, and successful approach to achieving a healthy and sustainable environment. Briefly, biochar acts as an efficient biosorbent for many PTEs in soils and waters. Furthermore, biochar can considerably reduce concentrations of herbicides in solutions. This review article explains the main reasons for the increasing levels of potentially toxic elements in the environment and their negative impacts on the ecosystem. Moreover, it briefly describes the advantages and disadvantages of using conventional methods for soil and water remediation then clarifies the reasons for using biochar in the clean-up practice of polluted soils and waters, either solely or in combination with other methods such as phytoremediation and soil washing technologies to attain more efficient remediation protocols for the removal of some PTEs, e.g., Cr and As from soils and water.

Physiochemical Analysis of Drinking Water and Treatment with a Homemade Filter: A Case Study of Illu Abba Bor Zone, Ethiopia

The drinking water quality was evaluated in order to provide a continuous supply of clean and safe drinking water for the preservation of public health. The study area consists of three villages: Tulube, Seddo, and Serdo, all of which are located near Mettu town, which is about 550 kilometers south-west of Ethiopia's capital, Addis Ababa. The physical and chemical parameters of the collected drinking water samples were assessed, including pH, turbidity, conductivity, total suspended solids (TSS), total dissolved solids (TDS), and the presence of heavy metals. The samples were examined in the laboratory, and the findings were compared to the World Health Organization (WHO) standards. Almost all of the physiochemical indicators were safe and within the permissible limit for drinking water quality. However, lead ion concentrations were found to be above the WHO standards. An adsorbent produced from banana pseudostems was used to remove lead ions from drinking water. The equilibrium parameters were determined using the Langmuir adsorption isotherm. The drinking water was treated for 4 h in a homemade adsorption column composed of filter medium (sand, charcoal, and powder of treated banana pseudostem). The data revealed that lead ions removal was nearly 70%, but still above the WHO standards.

The potential of polyethylene microplastics to transport copper in aquatic systems: Adsorption and desorption studies

Heavy metals and microplastics are two types of general contaminants that can cause significant damage to water systems and organisms. However, the interaction of heavy metal ions with microplastic in aquatic systems received less attention compared with that of organic contaminants. This study aims to explore the interaction of copper (II) ions with microplastic (polyethylene) in aquatic systems. The adsorption experiments were performed by varying several operational parameters including equilibrium pH, initial Cu (II) concentrations, and contact times. The microplastic was characterized using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared. The results confirmed the porous nature of the microplastic surface and the existence of various binding sites. The maximum Cu (II) uptake by microplastic was recorded as 1.23 mg/g at pH 5, according to the Langmuir adsorption isotherm. The experimental isotherm data exhibited a good fit to the Toth model, followed by the Langmuir and Freundlich equations, according to the correlation coefficient and %error values. The pseudo-first kinetics equation showed a better fit to copper (II) kinetics data compared with the pseudo-second kinetics equation. Elution of copper (II) ions from copper (II)-loaded microplastic was attempted using several elutants, and the results indicated that 0.01 M HNO₃ performed well with elution efficiency over 99.5%. Thus, the elution experiments furnished proof that Cu-loaded microplastic may leach Cu (II) ions under rich acidic conditions, thereby aiding the transport of Cu (II) ions into the digestive tracts of aquatic organisms. PRACTITIONER POINTS: Polyethylene microplastics showed potential to sorb copper ions. The mechanism was electrostatic interaction between microplastics and metal ions. Maximum copper adsorption by microplastic was recorded as 1.23 mg/g. Once desorbed, Cu(II) transferred into the digestive tracts of aquatic organisms.

Column optimization of adsorption and evaluation of bed parameters-based on removal of arsenite ion using rice husk

The objective of this study deals with column optimization of adsorption-based on removal of arsenite ion using rice husk. The parameters affecting the column adsorption study, i.e., influent-concentration, bed depth, and flow rate, were optimized. The range of parameters, i.e., influent-concentration (15-50 mg/L), flow rate (20, 35, 45, and 60 mL/min), and bed depth (15-60 mm), were studied experimentally. Kinetics models Bohart-Adams and Hutchins were studied to measure the amount adsorbed, depth of mass transfer zone, saturated concentration, and time observed at 10% & 90% breakthrough. The percentage amount adsorbed q_m enhanced with enhancement in bed depth but got reduced with influent ions concentration and volumetric flow rate. Established model Bohart-Adams and Hutchins equations were used for calculation of mass transfer zone which came out to be 51 mm. An adsorption capacity (q_m) of 4.5 mg/g for arsenite ions was achieved at optimum parameter values of 60 mm of bed depth, 20 mL/min volumetric flow rate, and 50 mg/L of influent ions concentration. The adsorption bed parameters were also evaluated using Hutchins and Michaels equations. The column study proved rice husk to be a potential adsorbent for the adsorption of arsenite.

Methylene Blue Adsorption BY UV-Treated Graphene Oxide Nanoparticles (UV/n-GO): Modeling and Optimization Using Response Surface Methodology and Artificial Neural Networks

To mitigate the negative effects of pollution produced by the growing levels of pollutants in the environment, research and development of novel and more effective materials for the treatment of pollutants originating from a variety of industrial sources should be prioritized. In this research, a UV-irradiated nano-graphene oxide (UV/n-GO) was developed and studied for methylene blue (MB) adsorption. Furthermore, the batch adsorption studies were modelled using response surface modelling (RSM) and artificial neural networks (ANNs). Investigations employing FTIR, XRD, and SEM were carried out to characterize the adsorbent. The best MB removal of 95.81% was obtained at a pH of 6, a dose of 0.4 g/L, an MB concentration of 25 mg/L, and a period of 40 min. This was accomplished with a desirability score of 0.853. A three-layer backpropagation network with an ideal structure of 4-4-1 was used to create an ANN model. The R2 and MSE values determined by comparing the modelled data with the experimental data were 0.9572 and 0.00012, respectively. The % MB removal predicted by ANN was 94.76%. The kinetics of adsorption corresponded well with the pseudo-second-order model (R2 > 0.97). According to correlation coefficients, the order of adsorption isotherm models is Redlich–Peterson > Temkin > Langmuir > Freundlich. Thermodynamic investigations show that MB adsorption was both spontaneous and endothermic.

Improved precision in As speciation analysis with HERFD-XANES at the As K-edge: the case of As speciation in mine waste

High-energy-resolution fluorescence-detected (HERFD) X-ray absorption near-edge spectroscopy (XANES) is a spectroscopic method that allows for increased spectral feature resolution, and greater selectivity to decrease complex matrix effects compared with conventional XANES. XANES is an ideal tool for speciation of elements in solid-phase environmental samples. Accurate speciation of As in mine waste materials is important for understanding the mobility and toxicity of As in near-surface environments. In this study, linear combination fitting (LCF) was performed on synthetic spectra generated from mixtures of eight measured reference compounds for both HERFD-XANES and transmission-detected XANES to evaluate the improvement in quantitative speciation with HERFD-XANES spectra. The reference compounds arsenolite (As2O3), orpiment (As2S3), getchellite (AsSbS3), arsenopyrite (FeAsS), kaňkite (FeAsO4·3.5H2O), scorodite (FeAsO4·2H2O), sodium arsenate (Na3AsO4), and realgar (As4S4) were selected for their importance in mine waste systems. Statistical methods of principal component analysis and target transformation were employed to determine whether HERFD improves identification of the components in a dataset of mixtures of reference compounds. LCF was performed on HERFD- and total fluorescence yield (TFY)-XANES spectra collected from mine waste samples. Arsenopyrite, arsenolite, orpiment, and sodium arsenate were more accurately identified in the synthetic HERFD-XANES spectra compared with the transmission-XANES spectra. In mine waste samples containing arsenopyrite and either scorodite or kaňkite, LCF with HERFD-XANES measurements resulted in fits with smaller R-factors than concurrently collected TFY measurements. The improved accuracy of HERFD-XANES analysis may provide enhanced delineation of As phases controlling biogeochemical reactions in mine wastes, contaminated soils, and remediation systems.

Treatment of Municipal Wastewater in a Fixed Aerated Bed: Use of Natural Fibrous Materials

The municipal wastewater may be treated using a number of different types of fixed beds that have a larger surface area. Since the fibrous materials have such a large specific surface area, they are frequently considered to be the best option for greater microbiological support and treatment efficacy. In this research, natural fibre materials such as coir fibre and areca husk were investigated for their potential to function as fixed aerated beds for the treatment of municipal wastewater. During the experiment, variations in the chemical oxygen demand (COD), biological oxygen demand (BOD), total dissolved solids (TDS), and total suspended solids (TSS) of the effluent were used to determine how well the aerated fixed bed work in treating the wastewater. The most efficient operating parameters for the successful treatment of wastewater were determined to be a contact period of 72 hrs, a filter medium depth of 5 cm, and a packing density of 10 kg/m³. The reductions in BOD, COD, TDS, and TSS for coir fibre are 55%, 58.8%, 57.8%, and 51.89%, respectively, whereas the reductions for areca husk are 38.3%, 37.78%, 31.76%, and 30.56%, respectively. In the course of this experiment, the coir fibre was discovered to be marginally more effective in comparison to the areca husk.

Seaweed’s Role in Energetic Transition—From Environmental Pollution Challenges to Enhanced Electrochemical Devices

Simple Summary

Earth is currently facing the effects of climate change in all environmental ecosystems; this, together with pollution, is the cause of species extinction and biodiversity loss. Thus, it is vital to take actions to mitigate and decrease the release of greenhouse gases to the atmosphere. The emergence of energetic transition from fossil fuels to greener energies is clearly defined in the United Nations 2030 agenda. Although this transition endorses the ambitious goal to supply greener energy for all developed societies, the increased demand for the minerals essential to develop cleaner energetic technologies has highlighted several economic and environmental issues. Currently, these minerals are mainly obtained by mining activities that generate high levels of soil and water pollution, coupled with the intensive use of water and hazardous gas release. On the other hand, the exponential increase of electronic waste derived from end-of-life electronic equipment is already raising environmental concerns due to heavy metal contamination as a result of their disposal. Thus, it is vital to develop sustainable and efficient strategies to mitigate energetic transition environmental footprints. This review highlights the use of seaweed biomass for toxic mineral bioremediation, recycling, and as an alternative material for greener energy-storage device development.

Abstract

Resulting from the growing human population and the long dependency on fossil-based energies, the planet is facing a critical rise in global temperature, which is affecting all ecosystem networks. With a growing consciousness this issue, the EU has defined several strategies towards environment sustainability, where biodiversity restoration and preservation, pollution reduction, circular economy, and energetic transition are paramount issues. To achieve the ambitious goal of becoming climate-neutral by 2050, it is vital to mitigate the environmental footprint of the energetic transition, namely heavy metal pollution resulting from mining and processing of raw materials and from electronic waste disposal. Additionally, it is vital to find alternative materials to enhance the efficiency of energy storage devices. This review addresses the environmental challenges associated with energetic transition, with particular emphasis on the emergence of new alternative materials for the development of cleaner energy technologies and on the environmental impacts of mitigation strategies. We compile the most recent advances on natural sources, particularly seaweed, with regard to their use in metal recycling, bioremediation, and as valuable biomass to produce biochar for electrochemical applications.

Algae bioprocess to deal with cosmetic chemical pollutants in natural ecosystems: A comprehensive review

Elevated demand and extensive exploitation of cosmetics in day-to-day life have hiked up its industrial productions worldwide. Organic and inorganic chemicals like parabens, phthalates, sulfates, and so forth are being applied as constituents towards the formulations, which tend to be the mainspring ecological complication due to their enduring nature and accumulation properties in various sections of the ecosystem. These cosmetic chemicals get accrued into the terrestrial and aquatic systems on account of various anthropogenic activities involving agricultural runoff, industrial discharge, and domestic effluents. Recently, the use of microbes for remediating persistent cosmetic chemicals has gained immense interest. Among different forms of the microbial community being applied as an environmental beneficiary, algae play a vital role in both terrestrial and aquatic ecosystems by their biologically beneficial metabolites and molecules, resulting in the biobenign and efficacious consequences. The use of various bacterial, fungal, and higher plant species has been studied intensely for their bioremediation elements. The bioremediating property of the algal cells through biosorption, bioassimilation, biotransformation, and biodegradation has made it favorable for the removal of persistent and toxic pollutants from the environment. However, the research investigation concerned with the bioremediation potential of the algal kingdom is limited. This review summarizes and provides updated and comprehensive insights into the potential remediation capabilities of algal species against ecologically hazardous pollutants concerning cosmetic chemicals.

Microwave-assisted catalytic hydrothermal carbonization of Laminaria japonica for hydrochars catalyzed and activated by potassium compounds

There are limited investigations describing preparation and application of alga-based hydrochars via microwave-assisted catalytic hydrothermal carbonization (MA-CHTC). Therefore, hydrochars were successfully prepared from macroalgae biomass Laminaria japonica impregnated with KH2PO4, KCl, K2CO3, and KOH as acidic, neutral salt, and alkaline catalysts, respectively, via the MA-CHTC. Comprehensive characterization of physicochemical properties of the hydrochars, including yields, elemental and phase composition, specific surface areas, functional groups, and morphology, confirmed different catalytic effects of these catalysts on hydrochar formation. Adsorption kinetics and isotherms of Pb(II) revealed significant improvement of adsorption capacities for Pb(II) due to synergetic chemical activation of the spiked catalysts. Therefore, the synergetic catalytic effects and chemical activation is benefic for tailored design of engineered hydrochars with different properties for special application through selection of catalysts during the MA-CHTC process.

Arsenic removal via a novel hydrochar from livestock waste co-activated with thiourea and γ-Fe2O3 nanoparticles

Arsenic (As) contaminants post tremendous threats to environment safety. Pristine hydrochar (PHC), thiourea-activated hydrochar (THC), and thiourea-Fe(NO₃)₃-activated hydrochar (Fe₂O₃@THC) were fabricated from dairy cattle manure via one-pot hydrothermal carbonization at 250 ℃ and applied for aqueous As(V) removal. Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were conducted to characterize hydrochars and As(V) adsorption. Thiourea increased N and S functional groups (-NH₂, C-N, C=S and S=O). Fe(NO₃)₃ introduced γ-Fe₂O₃ nanoparticles and provided Fe₂O₃@THC with Fe-O. The combination of thiourea and Fe(NO₃)₃ granted Fe₂O₃@THC with the largest surface area (33.45 m²/g), and the highest total pore volume (0.095 cm³/g) among three hydrochars. As(V) adsorption was a physicochemical process involving electrostatic attraction, complexation, ion exchange and H-bond interaction. The maximum As(V) adsorption capacities and partition coefficients decreased as follows: Fe₂O₃@THC (44.80 mg/g; 38.44 L/g) > THC (38.77 mg/g; 5.94 L/g) > PHC (19.05 mg/g; 1.17 L/g). Three hydrochars exhibited preferable reusability in NaOH solution with only 24.2%, 11.8% and 14.1% decrease in adsorption rates after four cycles for PHC, THC and Fe₂O₃@THC, respectively. Fe₂O₃@THC is a promising adsorbent for efficient As(V) removal. This study explored the efficient As(V) removal by activated hydrochars with future research potential.

Immobilization and retention of caffeine in soil amended with Ulva reticulata biochar

The goal of the present study was to evaluate the immobilization and retention of caffeine (CFN) in soil and the influence of biochar for the CFN transport in agricultural soil. The biochar was produced from the Ulva reticulata seaweed biomass (ULBC) under the slow-pyrolysis with a heating rate of 7 °C/min at 500 °C and characterized using XRD and FTIR. The CFN retention and transport abilities in loamy sand and ULBC amended (2.5%) soil were evaluated under various pH values range of 3-10 and at various CFN concentrations using batch and column experiments. The surface orientation of ULBC was portrayed as the randomized distribution of hetero and homogeneous nature. The highest retention capacity (40 μg/g) was obtained at pH 4.0. Soil amendment with ULBC shows a higher retention affinity towards CFN, of up to 150 μg/g than soil, with minimal pH dependence. The maximum CFN adsorption capacities of soil and amended soils were 420 and 820 μg/g, respectively, based on the Langmuir model. Batch experiments suggested the adsorption of CFN by the biochar amended loamy soil is governed by the electrostatic attraction. The column experiment data demonstrated a high transport potential of CFN in the loamy sand; however, a strong cumulative reduction of transport (58%) was observed with the application of ULBC into the loamy sand. Thus, the addition of seaweed biochar as an amendment in soils with biosolids and wastewater irrigation may reduce the mobilization of CFN to the aquatic system and possibly reduce plant uptake.

As(V) sorption from aqueous solutions using quaternized algal/polyethyleneimine composite beads

Composite beads (APEI*), obtained by the controlled interaction of algal biomass with PEI, followed by ionotropic gelation and crosslinking processes using CaCl₂/glutaraldehyde solution, constitute efficient supports for metal binding. The quaternization of algal/PEI beads (Q-APEI*) significantly increases the sorption properties of the composite beads (APEI*) for As(V). The materials are characterized by SEM/EDX, TGA, BET, elemental analysis, FTIR, XPS, and titration. The sorption of As(V) is studied in function of pH while sorption mechanism is discussed in function of metal speciation and surface characteristics of the sorbent. Optimum sorption occurs at pH close to 7. Fast uptake kinetics, correlated to textural properties are successfully fitted by pseudo-first order rate equation and the Crank equation (for resistance to intraparticle diffusion); equilibrium is reached with 45-60 min. The Langmuir equation finely fits sorption isotherms; maximum sorption capacity reaches 1.34 mmol As g^-1. Arsenic can be completely eluted using 0.5 M CaCl₂/0.5 M HCl solutions; the sorbent maintains high sorption and desorption efficiencies for a minimum of 5 cycles. The sorbent is tested for the removal of As(V) from mining effluents containing high concentration of iron and traces of zinc. At pH 3, the sorbent shows remarkable selectivity for As(V) over Fe. After controlling the initial pH to 5, a sorbent dosage of 2 g L^-1 is sufficient for achieving the complete recovery of As(V) from mining effluent (corresponding to initial concentration of 1.295 mmol As L^-1).