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•A broad overview of biochar/LDH-based materials in water purification is presented.•The potential of biochar/LDH for the uptake of pollutants is critically evaluated.•Adsorption ...mechanisms and regeneration capability of biochar/LDH are appraised.•The catalytic degradation of various pollutants by biochar/LDH is reviewed.•Challenges and prospects of biochar/LDH in water treatment are highlighted.
Biochar/layered double hydroxide (LDH) composites have gained considerable attention in recent times as low-cost sustainable materials for applications in water treatment. This paper critically evaluates the latest development in applications of biochar/LDH composites in water treatment with an emphasis on adsorption and catalytic degradation of various pollutants. The adsorption of various noxious contaminants, i.e., heavy metals, dyes, anions, and pharmaceuticals onto biochar/LDH composites are described in detail by elaborating the adsorption mechanism and regeneration ability. The synergistic effect of LDH with biochar exhibited significant improvement in specific surface area, surface functional groups, structure heterogeneity, stability, and adsorption characteristics of the resulting biochar/LDH composites. The major hurdles and challenges associated with the synthesis and applications of biochar/LDH composites in water remediation are emphasized. Finally, a roadmap is suggested for future research to assure the effective applications of biochar/LDH composites in water purification.
This study investigated the impact of pyrolysis conditions on physical characteristics of date palm fronds biochars and their performances for aqueous uptake of anionic dyes—methyl orange (MO) and ...Eriochrome Black-T (EBT)—and cationic dyes—methylene blue (MB) and crystal violet (CV). Detailed characterization of the biochars revealed the formation of oxygen functionalities (C=O, C-O-C, and C-O), improved surface characteristics (surface area and pore volume) and high ash content at higher pyrolysis temperature and time. Biochar-derived date palm with a high surface area of 431.82 m
2
/g and a pore volume of 0.134 cm
3
/g was obtained at pyrolysis temperature and time 700 °C and 4 h, respectively. For all the four investigated dyes, the adsorption isotherm was mainly described by Redlich–Peterson isotherm model (
R
2
> 0.95), while the adsorption kinetics well-fitted the pseudo-second order model. The biochar yielded fast dyes adsorption with maximum adsorption capacity for MB, EBT, MO, and CV dye of up to 206.61, 309.59, 163.132, and 934.57 mg/g at 200 mg/L dye concentration, respectively. The adsorption of cationic dyes was pH-independent indicating the involvement of pi–pi and chemical interactions. However, the uptake of the anionic dye was favorable at acidic conditions and was dominated by electrostatic interactions involving ion exchange and chemical reactions. The produced biochars exhibited excellent surface characteristics and enhanced adsorptive performance relative to other similar adsorbents. Thus, the direct pyrolysis of date palm fronds’ waste is a sustainable and economical approach of converting a huge quantity of wastes into excellent adsorbent for effective remediation of dye-contaminated water and wastewater.
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•A comprehensive overview of bioremediation in water treatment is presented.•The potential of microorganisms for the uptake of dyes are portrayed in detail.•Recent advancements in the ...bioreactors and microbial fuel cells are emphasized.•The major challenges in the bioremediation applications are accentuated.•A roadmap for future research is suggested.
Environmental pollution associated with the discharge of textile industries is becoming a global concern. There is an imperative need for developing efficient, environmentally friendly, and cost-effective techniques for treating the wastewater containing dyes. Bioremediation of dyes is a fascinating approach to treat the textile effluents as it offers many advantages over the conventional treatment techniques. This review critically evaluates the latest advancements in applications of bioremediation techniques for the removal of various dyes from wastewater. The applications of various microorganisms such as bacteria, algae, fungi, yeast, and enzymes for the uptake of dyes are portrayed in detail. The current advancements in the bioremediation of textile effluents, research opportunities, challenges, and future outlook are emphasized. It also highlights the progress in bioremediation of dyes using bioreactors and microbial fuel cells. This review is beneficial in understanding the current status of bioremediation in water purification and accelerating the research focusing the role of bioremediation in water purification applications in future.
The Kingdom of Saudi Arabia generates an enormous amount of date palm waste, causing severe environmental concerns. Green and strong concrete is increasingly demanded due to low carbon footprints and ...better performance. In this research work, biochar derived from locally available agriculture waste (date palm fronds) was used as an additive to produce high-strength and durable concrete. Mechanical properties such as compressive and flexural strength were evaluated at 7, 14, and 28 days for control and all other mixes containing biochar. In addition, the durability properties of the concrete samples for the mixes were investigated by performing electric resistivity and ultra-sonic pulse velocity testing. Finally, a SWOT (strengths, weaknesses, opportunities, and threats) analysis was carried out to make strategic decisions about biochar’s use in concrete. The results demonstrated that the compressive strength of concrete increased to 28−29% with the addition of 0.75−1.5 wt% of biochar. Biochar-concrete containing 0.75 wt% of biochar showed 16% higher flexural strength than the control specimen. The high ultrasonic pulse velocity (UPV) values (>7.79 km/s) and low electrical resistivity (<22.4 kΩ-cm) of biochar-based concrete confirm that the addition of biochar resulted in high-quality concrete free from internal flaws, cracks, and better structural integrity. SWOT analysis indicated that biochar-based concrete possessed improved performance than ordinary concrete, is suitable for extreme environments, and has opportunities for circular economy and applications in various construction designs. However, cost and technical shortcomings in biochar production and biochar-concrete mix design are still challenging.
A sewage sludge-based activated carbon (SBAC) intercalated MgAlFe ternary layered double hydroxide (SBAC-MgAlFe-LDH) composite was synthesized via the coprecipitation method. The adsorptive ...performance of the composite for phenol uptake from the aqueous phase was evaluated via the response surface methodology (RSM) modeling technique. The SBAC-MgAlFe-LDH phenol uptake capacity data were well-fitted to reduced RSM cubic model (R2 = 0.995, R2-adjusted = 0.993, R2-predicted = 0.959 and p-values < 0.05). The optimum phenol adsorption onto the SBAC-MgAlFe-LDH was achieved at 35 °C, 125 mg/L phenol, and pH 6. Under the optimal phenol uptake conditions, pseudo-first-order and Avrami fractional-order models provided a better representation of the phenol uptake kinetic data, while the equilibrium data models’ fitting follows the order; Liu > Langmuir > Redlich–Peterson > Freundlich > Temkin. The phenol uptake mechanism was endothermic in nature and predominantly via a physisorption process (ΔG° = −5.33 to −5.77 kJ/mol) with the involvement of π–π interactions between the phenol molecules and the functionalities on the SBAC-LDH surface. The maximum uptake capacity (216.76 mg/g) of SBAC-MgAlFe-LDH was much higher than many other SBAC-based adsorbents. The improved uptake capacity of SBAC-LDH was attributed to the effective synergetic influence of SBAC-MgAlFe-LDH, which yielded abundant functionalized surface groups that favored higher aqueous phase uptake of phenol molecules. This study showcases the potential of SBAC-MgAlFe-LDH as an effective adsorbent material for remediation of phenolic wastewater
Engineers are continuously looking to improve the performance of existing materials. Nanostructured cellulose (cellulose nanocrystals or nanocellulose) offers a high aspect ratio and mechanical ...strength that may support development of a new class of concrete adapted for extreme environmental conditions. In this study, we developed and tested various types of cellulose nanocrystal (CNC)-based concrete for application in the construction industry. Specifically, three CNC-based concrete specimens with different cellulose nanocrystal types and proportions were tested to understand the effects of nanocellulose on structural concrete performance. Destructive and nondestructive testing, along with surface morphology characterizations, were conducted to evaluate the performance of the CNC-based concrete specimens. The destructive and nondestructive tests yielded similar results. Higher CNC proportions improved the concrete’s microstructure and produced higher ultrasonic pulse velocities along the same path length. Furthermore, results from Schmidt hammer rebound tests confirmed that the CNC-based concrete specimens with higher crystallinity, higher aspect ratios, and rougher surfaces were able to sustain larger loads with smaller crack developments. Finally, results from rapid chloride permeability tests indicated that the addition of 0.25 wt% cellulose nanocrystals in the CNC-1 concrete specimen and 0.75 wt% cellulose nanocrystals in the CNC-2 concrete specimen produced the highest peak resistance against water and chloride ion penetration. These findings can guide future research and development of this novel and innovative material.
In this study, date-palm biochar MgAl-augmented double-layered hydroxide (biochar-MgAl-LDH) nanocomposite was synthesized, characterized, and used for enhancing the removal of phosphate and nitrate ...pollutants from wastewater. The biochar-MgAl-LDH had higher selectivity and adsorption affinity towards phosphate compared to nitrate. The adsorption kinetics of both anions were better explained by the pseudo-first-order model with a faster removal rate to attain equilibrium in a shorter time, especially at lower initial phosphate-nitrate concentration. The maximum monolayer adsorption capacities of phosphate and nitrate by the non-linear Langmuir model were 177.97 mg/g and 28.06 mg/g, respectively. The coexistence of anions (Cl
, SO
, NO
, CO
and HCO
) negligibly affected the removal of phosphate due to its stronger bond on the nano-composites, while the presence of Cl
and PO
reduced the nitrate removal attributed to the ions' participation in the active adsorption sites on the surface of biochar-MgAl-LDH. The excellent adsorptive performance is the main synergetic influence of the MgAl-LDH incorporation into the biochar. The regeneration tests confirmed that the biochar-MgAl composite can be restored effortlessly and has the prospective to be reused after several subsequent adsorption-desorption cycles. The biochar-LDH further demonstrated capabilities for higher removal of phosphate and nitrate from real wastewater.
This experimental work focused on the synthesis, characterization, and testing of a unique, magnetically separable, and eco-friendly adsorbent composite material for the advanced treatment and ...efficient removal of nitrate and phosphate pollutants from wastewater. The MgAl-augmented double-layered hydroxide (Mg-Fe/LDH) intercalated with sludge-based activated carbon (SBAC-MgFe) composites were characterized by FT-IR, XRD, BET, VSM, SEM, and TEM techniques, revealing homogeneous and efficient dispersion of MgFe/LDH within the activated carbon (AC) matrix, a highly mesoporous structure, and superparamagnetic characteristics. The initial solution pH, adsorbent dose, contact time, and temperature parameters were optimized in order to reach the best removal performance for both pollutants. The maximum adsorption capacities of phosphate and nitrate were found to be 110 and 54.5 mg/g, respectively. The competition between phosphate and coexisting ions (Cl−, CO32−, and SO42−) was studied and found to be remarkably lower in comparison with the nitrate adsorption. The adsorption mechanisms were elucidated by kinetic, isotherm, thermodynamic modeling, and post-adsorption characterizations of the composite. Modeling and mechanistic studies demonstrated that physisorption processes such as electrostatic attraction and ion exchange mainly governed the nitrate and phosphate adsorption. The composite indicated an outstanding regeneration performance even after five sequences of adsorption/desorption cycles. The fabricated composite with magnetically separable characteristics can be used as a promising adsorbent for the removal of phosphate and nitrate pollutants from wastewater.
Ternary layered double hydroxide, MgCoAl (MCA) and its graphene-based composite (G/MCA) were fabricated via a simple co-precipitation technique. The composites along with their calcined products ...(MCA-C) and (G/MCA-C) were used as adsorbents for the removal of an anionic dye, methyl orange (MO), from aqueous phase. The characterization results (scanning electron microscopy and transmission electron microscopy) revealed homogeneous dispersion of graphene onto the MCA. Calcination of G/MCA resulted in a rough and heterogeneous surface with significant improvement in oxygen functionalities and surface area, which plays a crucial role in improved dye adsorption performance. Adsorptive equilibrium was established at 240 min for MCA and G/MCA and 180 min for MCA-C and G/MCA-C respectively at pH 3 and optimum dosage of 10 mg. The Redlich-Peterson and Langmuir isotherm models closely describe the adsorption process with maximum adsorption capacities of 357.14, 384.62, 400.12 and 434.78 mg/g for MCA, G/MCA, MCA-C, and G/MCA-C respectively. Kinetics modeling indicates the adequacy and fitness of the pseudo-second-order model. A thermodynamics evaluation substantiates the exothermic nature of the adsorption processes. The MO-graphene ternary LDH composite adsorption process is controlled by several mechanisms including hydrogen bonding, surface adsorption, chemical and electrostatic interactions with surface reconstruction. The high removal efficiency of the MO coupled with high recovery and reusability of these nanomaterials showcases their potential for deployment in wastewater treatment.
In this study, jojoba seeds residues are investigated for the removal of anionic dyes (Eriochrome black T and Congo red) from aqueous phase after extraction of oil and defatting (washing with ...n-hexane) from them. The fatted (F-JR) and defatted (DF-JR) jojoba residues were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron spectroscopy, thermogravimetric and BET analyzer. The results indicated that the surface of F-JR and DF-JR exhibited abundant oxygen functionalities (O–H, C–O, C=O, C–O–C) with highly porous surface morphology. The adsorption results showed that the removal of EBT and CR was significantly affected by solution pH and maximum removal of both dyes (EBT and CR) was obtained at pH 2 and 6, respectively, with equilibrium reached at 600 min. The kinetic results were best fitted with pseudo-second-order model. The Freundlich isotherm model well described the EBT adsorption, whereas CR adsorption better matches the Langmuir isotherm model for both F-JR and DF-JR. The maximum adsorption of EBT and CR was found to be 88.96 and 24.64 and 113.50 and 58.82 mg/g onto F-JR and DF-JR, respectively. The adsorption mechanism of EBT and CR mainly involved electrostatic attraction, chemical reactions, pi-pi interactions and development of hydrophobic forces. The adsorbent showed better removal performance of dyes, when compared to other agriculture residues, indicating potential and beneficial utilization of jojoba residues for effective decontamination of dye-contaminated wastewater.
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