Facile synthesis of economical feasible fly ash-based zeolite-supported nano zerovalent iron and nickel bimetallic composite for the potential removal of heavy metals from industrial effluents

Biogenic engineered zinc oxide nanoparticle for sulfur black dye removal from contaminated wastewater: comparative optimization, simulation modeling, and isotherms

This research work aimed to isolate and culture the bacterium Bacillus paramycoides for biogenic fabrication of zinc oxide nanoparticles, specifically ZnO and ZnO-ME nanoparticles (nanoparticles fabricated from bacterial extracts only - ZnO, and from bacterial cell mass including extract - ZnO-ME). SEM investigation revealed the spherical-shaped NPs with 22.33 and 39 nm in size for ZnO and ZnO-ME, respectively. The Brunauer, Emmett, and Teller (BET) studies revealed mesoporous structure with pore diameters of 13.839 and 13.88 nm and surface area of 7.617 and 33.635 m2/gm for ZnO and ZnO-ME, respectively. Various parameters for the adsorption of sulfur black dye onto both ZnO and ZnO-ME were screened and optimized using Plackett-Burman Design (PBD), Full Factorial Design (FFD) and Central Composite Design (CCD). The results of the optimization modeling study revealed that FFD yielded the most predictable and best-fitting results among all the models studied, with R2 values of 0.998 for ZnO and 0.993 for ZnO-ME. Notably, ZnO-ME exhibited a greater dye removal efficiency 80% than ZnO i.e., 71%, it may be due to the presence of amorphous carbon on the surface of ZnO-ME. Among the various isothermal models, the Freundlich model displayed the strongest correlation with the dye removal data, confirming the multilayer adsorption of dye on both nanoparticles and supporting physisorption. Therefore, ZnO and ZnO-ME nanoparticles have been proven as potential tools for mitigating environmental impacts associated with dye-containing wastewater.

Effective chromium removal of metal anchored alginate-chitosan binary bio-composites

Water is the most essential resource for the biotic and abiotic components of an ecosystem. Any change in the quality of this water may cause adverse impact on the ecosystem. Hexavalent chromium is one such important pollutant that gets exposed in the water mainly through anthropogenic processes. Adsorption is considered to be an effective, economic and easiest method for remediation of such pollutants. Amongst the innumerable adsorbents available, biopolymers fetch the interest due to its cost effectiveness, efficiency and biocompatibility. But, the mechanical strength and workability of such biopolymers makes it unfit to use as an adsorbent. To improve these drawbacks, synthesis of biopolymeric composites become the need of the hour. So, an attempt was made here to synthesize metal cross-linked binary bio-composites using Alginate and Chitosan polymer matrix. Synthesized bio-composites were characterised with the aid of FTIR, XPS, Thermal analysis, SEM with EDAX and subjected for hexavalent chromium removal from water. Analysis of variance (ANOVA) with 95 % confidence intervals was used to assess the significance of independent variables and their interactions. Adsorption studies were done using batch process and to achieve greater sorption, various influencing parameters were optimized one by one. While investigating one parameter, other parameters were kept unaltered. Optimization was done for the parameters like contact time, dosage of the adsorbent, pH of the medium and presence of co-ions. Contact time and dosage for all the composites was 30 mins and 0.1 g respectively. Amongst the composites, Zirconium loaded binary composite possess high sorption capacity of around 14.8 mg/g. While Calcium and Iron loaded composites exhibit sorption capacity of around 9.8 mg/g and 10.4 mg/g respectively. Presence of other co-ions in the medium doesn't affect the sorption process. Isothermal studies infer the adsorption follows Langmuir model and thermodynamic parameters concludes the endothermic and randomness of the adsorption. The bio-composites can be recycled and used upto three cycles. Field trial was conducted and the composites work well in such conditions.

New insights in food security and environmental sustainability through waste food management

Food waste has been identified as one of the major factors that constitute numerous anthropogenic activities, especially in developing countries. There is a growing problem with food waste that affects every part of the waste management system, from collection to disposal; finding long-term solutions necessitates involving all participants in the food supply chain, from farmers and manufacturers to distributors and consumers. In addition to food waste management, maintaining food sustainability and security globally is crucial so that every individual, household, and nation can always get food. "End hunger, achieve food security and enhanced nutrition, and promote sustainable agriculture" are among the main challenges of global sustainable development (SDG) goal 2. Therefore, sustainable food waste management technology is needed. Recent attention has been focused on global food loss and waste. One-third of food produced for human use is wasted every year. Source reduction (i.e., limiting food losses and waste) and contemporary treatment technologies appear to be the most promising strategy for converting food waste into safe, nutritious, value-added feed products and achieving sustainability. Food waste is also employed in industrial processes for the production of biofuels or biopolymers. Biofuels mitigate the detrimental effects of fossil fuels. Identifying crop-producing zones, bioenergy cultivars, and management practices will enhance the natural environment and sustainable biochemical process. Traditional food waste reduction strategies are ineffective in lowering GHG emissions and food waste treatment. The main contribution of this study is an inventory of the theoretical and practical methods of prevention and minimization of food waste and losses. It identifies the trade-offs for food safety, sustainability, and security. Moreover, it investigates the impact of COVID-19 on food waste behavior.

Sequestration of Ni (II), Pb (II), and Zn (II) utilizing biogenic synthesized Fe3O4/CLPC NCs and modified Fe3O4/CLPC@CS NCs: Process optimization, simulation modeling, and feasibility study

The present study reports low-cost novel biogenic magnetite Citrus limetta peels carbon (Fe3O4/CLPC) nanocomposites and modified Fe3O4/CLPC@CS nanocomposites cross-linked with glutaraldehyde and subsequently employed in batch mode sequestration of heavy metals ions. Diverse techniques fully characterized them, and the influence of operating variables on adsorption reactions from aqueous solutions was investigated. The Brunauer, Emmett, and Teller (BET) surface areas of synthesized Fe3O4/CLPC and Fe3O4/CLPC@CS NCs were 53.91 and 32.16 m2/g, while the mesoporous diameters were 7.69 and 7.57 nm, respectively. The Langmuir isotherm and Pseudo second order kinetic were well-fitting and capable of explaining the adsorption reaction. The Langmuir-based monolayer adsorption (qmax) for Fe3O4/CLPC@CS NCs was 82.65, 95.24, and 64.10 mg/g, higher than Fe3O4/CLPC NCs, which were 70.92, 84.75, and 59.17 mg/g for Ni (II), Pb (II), and Zn (II), respectively. Each metal's pseudo second order correlation coefficient (R2 ≥ 0.99) reveals that nanocomposites surface binding functional groups controlled the adsorption rate via chemisorption. Further, thermodynamic results confirm that each studied metal ions' adsorption was spontaneous, endothermic, and characterized by an increase in randomness. In addition to magnetic separability, three ad-desorption cycles yielded exceptional adsorption efficacy and > 93% regenerability. The present study also reveals the effective utilization of Fe3O4/CLPC and Fe3O4/CLPC@CS NCs as cost-effective magnetic separable green adsorbents for heavy metals sequestration from electroplating wastewater.

Green synthesis and characterization of iron oxide nanoparticles for the removal of heavy metals (Cd2+ and Ni2+) from aqueous solutions with Antimicrobial Investigation

Clove and green Coffee (g-Coffee) extracts were used to synthesize green iron oxide nanoparticles, which were then used to sorb Cd²⁺ and Ni²⁺ ions out of an aqueous solution. Investigations with x-ray diffraction, Fourier-transform infrared spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, nitrogen adsorption and desorption (BET), Zeta potential, and scanning electron microscopy were performed to know and understand more about the chemical structure and surface morphology of the produced iron oxide nanoparticles. The characterization revealed that the main component of iron nanoparticles was magnetite when the Clove extract was used as a reducing agent for Fe³⁺, but both magnetite and hematite were included when the g-Coffee extract was used. Sorption capacity for metal ions was studied as a function of sorbent dosage, metal ion concentration, and sorption period. The maximum Cd²⁺ adsorption capacity was 78 and 74 mg/g, while that of Ni²⁺ was 64.8 and 80 mg/g for iron nanoparticles prepared using Clove and g-Coffee, respectively. Different isotherm and kinetic adsorption models were used to fit experimental adsorption data. Adsorption of Cd²⁺ and Ni²⁺ on the iron oxide surface was found to be heterogeneous, and the mechanism of chemisorption is involved in the stage of determining the rate. The correlation coefficient R² and error functions like RMSE, MES and MAE were used to evaluate the best fit models to the experimental adsorption data. The adsorption mechanism was explored using FTIR analysis. Antimicrobial study showed broad spectrum antibacterial activity of the tested nanomaterials against both Gram positive (S. aureus) (25923) and Gram negative (E. coli) (25913) bacteria with increased activity against Gram positive bacteria than Gram negative one and more activity for Green iron oxide nanoparticles prepared from Clove than g-Coffee one.

Systematic studies on the effect of structural modification of orange peel for remediation of phenol contaminated water

In the present study, orange peel biochar has been utilized as the adsorbent for the removal of phenol from contaminated water. The biochar was prepared by thermal activation process at three different temperature 300, 500 and 700°C and are defined as B300, B500, and B700 respectively. The synthesized biochar has been characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformation infrared spectroscopy (FTIR), RAMAN spectroscopy, X-ray photoelectron spectroscopy (XPS), and UV-Vis spectroscopy. SEM analysis revealed a highly irregular and porous structure for B700 as compared with others. The parameters such as initial phenol concentration, pH, adsorption dosage, and contact time were optimized, and the maximum adsorption efficiency and capacity of about 99.2% and 31.0 mg/g was achieved for B700 for phenol adsorption. The Branauer-Emmett-Teller (BET) surface area and Berrate-Joyner-Halenda (BJH) pore diameter obtained for B700 were about 67.5 m² /g and 3.8 nm. The adsorption of phenol onto the biochar followed Langmuir isotherm showing linear fit with R²  = 0.99, indicating monolayer adsorption. The kinetic data for adsorption is best fitted for pseudo-second order. The thermodynamic parameters ΔG°, ΔH°, and ΔS° values obtained are negative, which means that the adsorption process is spontaneous and exothermic. The adsorption efficiency of phenol marginally declined from 99.2% to 50.12% after five consecutive reuse cycles. The study shows that the high-temperature activation increased the porosity and number of active sites over the orange peel biochar for efficient adsorption of phenol. PRACTITIONER POINTS: Orange peel is thermally activated at 300, 500, and 700°C for structure modification. Orange peel biochars were characterized for its structure, morphology, functional groups, and adsorption behavior. High-temperature activation improved the adsorption efficiency up to 99.21% due to high porosity.

Effective adsorption of ammonium nitrogen by sulfonic-humic acid char and assessment of its recovery for application as nitrogen fertilizer

Ammonium nitrogen (NH₄⁺-N) is a form of N that is non-negligible in eutrophication water as well as an essential nutrient for plants growing. Carbon materials are considered superior for the adsorption recovery of excess NH₄⁺-N in water bodies. The sulfonic-humic acid char (SHAC) was prepared from humic acid (HA) by pyrolysis and hydrothermal grafting with sodium allyl sulfonate. SEM-mapping, FTIR and XPS results indicated that sulfonic groups (-SO₃H) were successfully grafted onto SHAC. The adsorption kinetic fitting displayed that the adsorption of NH₄⁺-N by SHAC conformed to the pseudo-second-order kinetics and could reach equilibrium in about 100 min. The maximum adsorption of NH₄⁺-N by SHAC was 77.24 mg/g, it was mainly contributed by electrostatic attraction, hydrogen bonding and pore volume sites. SHAC adsorption of NH₄⁺-N resulted in the material SHAC-N, which desorption rate was considerably slower than that of commercially available ammonium chloride (NH₄Cl) fertilizer and in accordance with the first order model. Wheat growth experiments revealed that the quality of wheat treated with SHAC-N (higher 100-grain weight and lower nitrate content) was better than that of NH₄Cl fertilizer. In addition, the higher residual NH₄⁺-N in the SHAC-N treatment soil facilitated subsequent crop planting. These results indicated that SHAC has excellent adsorption and slow release of NH₄⁺-N, and has great potential application for N management in environment and agriculture.

Magnetic nanofluid based on green deep eutectic solvent for enrichment and determination of chloramphenicol in milk and chicken samples by high-performance liquid chromatography-ultraviolet: Optimization of microextraction

In this work, magnetic nanofluid based on a deep eutectic solvent that constricts through a simple and easy route, and subsequently applied for the preconcentration and microextraction of chloramphenicol (CAP) as a hazardous drug from milk and chicken samples via syringe-to-syringe microextraction prior to its determination by high-performance liquid chromatography-ultraviolet (HPLC-UV). In addition, the optimum conditions of effective factors were searched by the central composite design (CCD), and subsequently, at their optimum value, the figures of merit were evaluated. Also, the suggested method illustrated a low limit of detection (0.2 ng mL^-1), a low limit of quantitation (0.67 ng mL^-1), and a good linear range with an R² of 0.996. The CAP relative recoveries in milk and chicken samples were 90.3%-95.1%, with relative standard deviations lower than 4.2%. The current enhancement technique is simple, easy, and rapid, which makes it suitable for quantification of CAP by HPLC-UV at trace levels in complicated materials with reliable and reproducible results.

Nanotechnology- A ray of hope for heavy metals removal

Environmental effects of heavy metal pollution are considered as a widespread problem throughout the world, as it jeopardizes human health and also reduces the sustainability of a cleaner environment. Removal of such noxious pollutants from wastewater is pivotal because it provides a propitious solution for a cleaner environment and water scarcity. Adsorption treatment plays a significant role in water remediation due to its potent treatment and low cost of adsorbents. In the last two decades, researchers have been highly focused on the modification of adsorption treatment by functionalized and surface-modified nanomaterials which has spurred intense research. The characteristics of nano adsorbents attract global scientists as it is also economically viable. This review shines its light on the functionalized nanomaterials application for heavy metals removal from wastewater and also highlights the importance of regeneration of nanomaterials in the view of visualizing the economic aspects along with a cleaner environment. The review also focused on the proper disposal of nanomaterials with crucial issues that persist in the adsorption process and also emphasize future research modification at a large-scale application in industries.

A Continuous Fixed Bed Adsorption Process for Fez City Urban Wastewater Using Almond Shell Powder: Experimental and Optimization Study

This study deals with the valorization of a biomaterial, almond shell, for the treatment of urban effluents of the city of Fez by a fixed bed column adsorption process. A parametric analysis of the process is carried out with conditions such as particle size, pH and height of the adsorbent bed to evaluate the optimal removal percent and obtain an optimal removal capacity of the adsorbent load. Characterization of the adsorbent prior to continuous adsorption was carried out by X-ray diffraction, Fourier-transform infrared spectrometry and scanning electron microscopy. The adsorption treatment seems to be influenced by certain parameters, such as the particle size of the biomaterial used, the height of the adsorption bed and the pH. The results suggest that this biomaterial can be used as a less expensive, available, biodegradable and very effective adsorbent to eliminate the load of urban waters on a small scale and why not on a large scale to replace chemicals in the treatment and to recover waste such as almond shell. The parameters measured reached maximum values varying between 82% for COD, 79% for EC and 71% for nitrite under well-defined operating conditions, with a particle size of 0.063 mm, a height column height of 7 cm and a pH of 6.5.

Application of magnetic carbon nanocomposite from agro-waste for the removal of pollutants from water and wastewater

Water pollution has significant impact on water usage, and various contaminants, such as organic and inorganic compounds, heavy metals, dyes, pharmaceuticals compounds, pathogens and radioactive compounds, are implicated. The quest for globalisation, structural developments and other related anthropogenic activities promote the release of contaminants that induce water pollution. Hence, treatment and remediation options that can remove pollutants from watercourses and wastewater have been developed. Applied nanotechnology using carbon nanocomposites has recently drawn attention because it has the advantages of low preparation cost, high surface area, pore volume and environmental stability. Magnetic carbon nanocomposites usually exhibit excellent performance in adsorbing contaminants from aqueous solutions, and thus expanding the use of nanotechnology in water treatment is of great importance. Therefore, this review explores the geographical outlook of water pollution, sources of water pollution and types of contaminants found in water and discusses the use of carbon nanocomposites as an emerging sustainable technology for water pollutant removal. The various properties of carbon-based composites influence the extent of pollutant adsorption during water treatment processes. Most carbon-based nanocomposites are generated from biomass produced by agro-waste materials. Magnetic activated carbon nanocomposites produced from walnut shells and rice husk waste can remove 78% of Cd(II) from contaminated aqueous systems. Magnetic nanocomposites from peanut shell, tea waste, curcumin nanoparticles, sunflower head waste, rice husk, hydrophyte biomass, palm waste and sugarcane bagasse facilitate hydrothermal carbonisation, chemical precipitation, co-precipitation, chemical activation, calcination and fast pyrolysis. These nanocomposites have benefitted wastewater treatment by increasing efficiency in removing pharmaceutical, dye and organic contaminants, such as promazine, ciprofloxacin, amoxicillin, rhodamine 6G, methyl blue, phenol and phenanthrene. Hence, this review discusses the relatively low costs, good biocompatibility, large surface-to-volume ratio, magnetic separation capability and reusability carbon materials and highlights the advantages of using magnetic carbon nanocomposites in the removal of contaminants from water or wastewater through adsorption mechanisms.

Enhanced remediation of lead (II) and cadmium (II) ions from aqueous media using porous magnetic nanocomposites - A comprehensive review on applications and mechanism

Lead and Cadmium, identified as toxic heavy metals, cause significant imbalance in the eco-system due to their tendency to bioaccumulate. Remediation of heavy metals by conventional adsorptive materials suffer demerits related to low efficiency or removal. Among the variety of adsorbent materials used in the adsorption process, metal oxides- and graphene oxide magnetic nanocomposites have gained a considerable attention. The use of nanomaterials may help to reduce this contamination, but after use, they are difficult to remove from water. An added magnetic property to nanomaterials facilitates their retrieval after use. The magnetic properties of these hybrid magnetic nanocomposites, coupled with unique characteristics of organic and inorganic elements, have found extensive application in water treatment technology. Detailed discussion on functionalisation of magnetic nanocomposites and the enhanced performance are presented. Magnetic graphene oxide-covalently functionalized-tryptophan was reported to have the highest adsorption capacity of 766.1 mg/g for remediation of lead (II) ions and graphene oxide exhibited the highest adsorption capacity of 530 mg/g for Cd (II) ions. The adsorption mechanisms for heavy metal ions on the surface of novel adsorbents, particularly lead and cadmium, using magnetic nanocomposites have been explained with reference to the isotherm models studied. The future scope of research in this area of research is proposed.

Novel GO/Fe-Mn hybrid for the adsorptive removal of Pb(II) ions from aqueous solution and the spent adsorbent disposability in cement mix: compressive properties and leachability study for circular economy benefits

GO/Fe-Mn hybrids were prepared by a single-pot chemical precipitation method and were characterized using FTIR, XRD, Raman, zeta potential, and FESEM, which confirmed the impregnation of Fe/Mn onto GO sheets. The synthesized hybrids were successively applied in removing the Pb(II) ions from aqueous solution and later utilizing the spent adsorbent to increase the properties of cement. The adsorption capability of the synthesized hybrid was seen in a set of batch studies to find out that about 15 min of contact time was required to remove 99% of the contaminant at a pH of 5 ± 0.2 and a dose of 0.83 g/L. The mechanism of the adsorption process for the synthesized hybrid was well described by Elovich kinetic model with an R² of 0.99 and Langmuir isotherm model, also with an R² of 0.99. The desorption studies conducted using 0.1 M HCl solution showed significant stability of the hybrid with a drop of 12% in the removal efficiency of Pb after up to five adsorption-desorption cycles. This points to an efficient adsorbent having potential for economical use. Later, the spent adsorbent was mixed with cement at ratios of 0.05%, 0.1%, and 0.5%, and compressive strength tests were performed, which showed an increase in the strength by 7.62%, 16.11%, and 26.82% at 28 days of curing time. The TCLP and SPLP tests performed on the hybrid and cement-spent adsorbent mix showed all the leaching parameters were well within the permissible limits. This development shows the potential for the use of spent adsorbent in a circular economy model.

Magnesium ferrite-nitrogen-doped graphene oxide nanocomposite: effective adsorptive removal of lead(II) and arsenic(III)

Magnetic nanocomposites have received immense interest as adsorbents for water decontamination. This paper presents adsorptive properties of nitrogen-doped graphene oxide (N-GO) with magnesium ferrite (MgFe₂O₄) magnetic nanocomposite for removing lead(II) (Pb(II)and arsenite As(III) ions. Transmission electron microscope (TEM) image of synthesized nanocomposite revealed the wrinkled sheets of N-GO containing MgFe₂O₄ nanoparticles (NPs) with particle size of 5-15 nm distributed over its surface. This nanocomposite displayed higher BET surface area (72.2 m²g^-1) than that of pristine MgFe₂O₄ NPs (38.4 m²g^-1). Adsorption on the nanocomposite could be described by the Langmuir isotherm with the maximum adsorption capacities were 930 mg/g, and 64.1 mg/g for Pb(II) and As(III), respectively. Whereas, maximum removal efficiencies were observed to be 99.7 [Formula: see text] 0.2% and 93.5 [Formula: see text] 0.1% for Pb(II) and As(III), respectively. The study on the effect of coexisting anions on the adsorption of metal ions showed that the phosphate ions were potential competitors of Pb(II) and As(III) ions to adsorb on the nanocomposite. Significantly, the investigation on adsorption of metal ion in the presence of coexisting heavy metal ions indicated the preferential adsorption of Pb(II) ions as compared to Cd(II), Zn(II) and Ni(II) ions. The effectiveness of the nanocomposite to remove the metal ions in electroplating wastewater was demonstrated.

Aspergillus tamarii mediated green synthesis of magnetic chitosan beads for sustainable remediation of wastewater contaminants

The release of different hazardous substances into the water bodies during the industrial and textile processing stages is a serious problem in recent decades. This study focuses on the potentiality of Fe3O4-NPs-based polymer in sustainable bioremediation of toxic substances from contaminated water. The biosynthesis of Fe3O4-NPs by A. tamarii was performed for the first time. The effect of different independent variables on the Fe3O4-NPs production were optimized using Plackett-Burman design and central composite design (CCD) of Response Surface Methodology. The optimum Fe3O4-NPs production was determined using incubation period (24 h), temperature (30 °C), pH (12), stirring speed (100 rpm) and stirring time (1 h). The incorporation of Fe3O4-NPs into chitosan beads was successfully performed using sol-gel method. The modified nanocomposite exhibited remarkable removal capability with improved stability and regeneration, compared to control beads. The optimal decolorization was 94.7% at 1.5 g/l after 90 min of treatment process. The reusability of biosorbent beads displayed 75.35% decolorization after the 7th cycle. The results showed a highly significant reduction of physico-chemical parameters (pH, TDS, TSS, COD, EC, and PO4) of contaminated wastewater. The sorption trials marked Fe3O4-NPs-based biopolymer as efficient and sustainable biosorbent for the elimination of hazardous toxic pollutants of wastewater in a high-speed rate.

Plant-Derived Iron Nanoparticles for Removal of Heavy Metals

Nanoparticle synthesis has seen exponential development recently as its characteristics of high surface area, high rate of adsorption, and easy, cost-effective synthesis have been exploited for the purpose of ground water purification via the removal of organic and inorganic compounds, along with the removal of heavy metals and microbes. The synthesis of Zero-Valent Iron Nanoparticles (ZVI NPs) by green methods has proved to be environmentally friendly in many ways as it employs the use of naturally occurring plant extracts. These nanoparticles have large surface areas and efficiently remove heavy metals. The reducing potential of these ZVI NPs is mostly −0.44 V, thus allowing them to reduce heavy metal compounds such as cadmium, lead, zinc, copper, and arsenic present in wastewater. Irradiated nanoparticles have also exhibited antimicrobial resistance and adsorption. It is also observed that nanoparticles show a higher rate of efficacy at a lower pH. The adsorbent, which is ZVI NPs in this case, when present in large doses reduces heavy metal compounds rapidly and effectively.

Removal of Pb2+ from synthetic aqueous solution using hydroxyapatite and hydroxyapatite@AD37 composite materials

In this paper, a simple method was proposed to obtain hydroxyapatite (HA) and hydroxyapatite/partially hydrolysed polyacrylamide (HA/AD37) composite materials which where applied to lead retention from aqueous solution by means of the batch method. The characterization of the materials verified that the presence of AD37 created interconnected porosity in the composite HA/AD37 giving it a good swelling properties that conducted to an easy separation of the material from aqueous solutions. Retention experiments carried out by varying the dose of lead and the contact time between adsorbent and adsorbate showed that the maximum adsorption capacity (Qmax) obtained for 2072.2 mg/L as initial concentration of Pb2 + was equal to 984.63 mg/g for HA and 924.50 mg/g for HA/AD37. Furthermore, AD37 used alone cannot retain Pb2 + ions. Indeed, the calculated Qmax of AD37 part of the composite was of 806.57 mg/g. The obtained Qmax values was elevated more than the reported values in many literatures. Based on the correlation coefficient, the kinetic study proved that pseudo-second order model agrees well with the obtained experimental data for Pb2+ retention by both HA and HA/AD37. Also, isotherm study explored that adsorption of lead was best fitted by Langmuir model for HA and Temkin model for HA/AD37. At last, the mechanism of retention was probed by characterizing the adsorbents after contact with lead ions by XRD and SEM. The results showed the transformation of calcium-hydroxyapatite to different structures of lead hydroxyapatite confirming the presence of ion exchange mechanism between Ca2+ and Pb2+.

The Utilization of Algae and Seaweed Biomass for Bioremediation of Heavy Metal-Contaminated Wastewater

The presence of heavy metals in water bodies is linked to the increasing number of industries and populations. This has serious consequences for the quality of human health and the environment. In accordance with this issue, water and wastewater treatment technologies including ion exchange, chemical extraction, and hydrolysis should be conducted as a first water purification stage. However, the sequestration of these toxic substances tends to be expensive, especially for large scale treatment methods that require tedious control and have limited efficiency. Therefore, adsorption methods using adsorbents derived from biomass represent a promising alternative due to their great efficiency and abundance. Algal and seaweed biomass has appeared as a sustainable solution for environmentally friendly adsorbent production. This review further discusses recent developments in the use of algal and seaweed biomass as potential sorbent for heavy metal bioremediation. In addition, relevant aspects like metal toxicity, adsorption mechanism, and parameters affecting the completion of adsorption process are also highlighted. Overall, the critical conclusion drawn is that algae and seaweed biomass can be used to sustainably eliminate heavy metals from wastewater.

Mechanism and isotherm modeling of effective adsorption of malachite green as endocrine disruptive dye using Acid Functionalized Maize Cob (AFMC)

Cationic Malachite green has been identified as a candidate for the endocrine disruptive compound found in the environment. In this study, the mechanism and isotherm modeling of effective adsorption of cationic malachite green dye onto acid-functionalized maize cob (AFMC) was investigated by batch technique. The operational parameters such as initial concentration (100–600 mg/L); contact time (10–120 min) and pH (3–10) influenced the removal efficiency and quantity adsorbed. A maximum of 99.3% removal efficiency was obtained at optimum conditions. AFMC physicochemical properties (surface area 1329 m²/g and particle size 300 μm < Ф < 250 μm) enhanced its efficiency. Based on R² > 0.97 and consistently low values of adsorption statistical error functions (ASEF), equilibrium data were best fitted to Freundlich isotherm. Kinetic data were best described by a pseudo-second-order model with consistent R² > 0.98 and validated by ASEF. The mechanism of the process was better described by intraparticle diffusion. Evidence of the adsorption process was confirmed by the change in morphology via Scanning Electron Microscopy (SEM) and surface chemistry by Fourier Transform infrared (FTIR). The performance of AFMC enlisted it as a sustainable and promising low-cost adsorbent from agro-residue for treatment of endocrine disruptive dye polluted water.

Removal of Pb2+ Ions by ZSM-5/AC Composite in a Fixed-Bed Bench Scale System

This investigation suggests the implementation of ZSM-5 activated carbon composite as a prolific adsorbent for the continuous elimination of Pb2+ ions from water. Continuous adsorption experiments were performed by varying three parameters such as process flow rate (2-6 mL min-1), bed height (2-6 cm), and initial concentration (250–750 mg L-1). The highest loading capacity of the fixed-bed 213.3 mg L-1 was achieved with optimal values of 2 mL min-1 of flow rate, bed height of 6 cm, and initial concentration of 750 mg L-1, respectively. The breakthrough curves and saturation points were found to appear quickly for increasing flow rates and initial concentration and vice versa for bed depth. The lower flow rates with higher bed depths have exhibited optimal performances of the fixed-bed column. The mechanism of adsorption of Pb2+ ions was found to be ion exchange with Na+ ions from ZMS-5 and pore adsorption onto activated carbon. The breakthrough curves were verified with three well-known mathematical models such as the Adams-Bohart, Thomas, and Yoon-Nelson models. The later models showed the best fit to the column data over the Adams-Bohart model that can be utilized to understand the binding of Pb2+ ions onto the composite. Regeneration of ZSM-5/activated carbon was achieved successfully with 0.1 M HCl within 60 min of contact time. The outcomes conclude that ZSM-5 activated carbon composite is a prolific material for the continuous removal of water loaded with Pb2+ ions.

Facile synthesis and characterization of polypyrrole - iron oxide - seaweed (PPy-Fe3O4-SW) nanocomposite and its exploration for adsorptive removal of Pb(II) from heavy metal bearing water

Lead is a widely used heavy metal which is highly toxic to kidney, nervous system and reproductive system. A special featured polypyrrole based adsorbent, with admirable salinity confrontation, environmental stability and reusability, was engaged to remove lead ions from aqueous solution. The advantages of using polypyrrole based adsorbent for heavy metal removal are: ease of synthesis, biocompatibility and high metal selectivity. In this study, polypyrrole - iron oxide - seaweed nanocomposite was proposed to remove lead ions from aqueous solution. A new method was adopted for the synthesis of polypyrrole - iron oxide - seaweed nanocomposite. The nanocomposite was prepared within a short time using ultra-assisted polymerization technique. The synthesized nanocomposite adsorbent was characterized using FTIR, SEM, TEM, EDS, XRD, XPS and zeta potential analysis. The adsorption capability of polypyrrole - iron oxide - seaweed nanocomposite towards lead was explored. The influence of pH, contact time, adsorbent dosage, metal ion concentration and recyclability were investigated. The optimum condition of these parameters was found to be: pH- 5, temperature - 40 °C, initial concentration - 100 mg/L and contact time - 20 min and the results showed that the hybrid composite adsorbed 97.25% Pb (II). Different isotherms such as Langmuir, Freundlich, Temkin and D-R models were also studied for the adsorption of Pb ions. The kinetics of the adsorption process was examined by I order, II order and intra particle diffusion kinetic models. The mechanism of lead adsorption onto the nanocomposite was also explored.

Artificial neural networks modeling for lead removal from aqueous solutions using iron oxide nanocomposites from bio-waste mass

Heavy metal ions in aqueous solutions are taken into account as one of the most harmful environmental issues that ominously affect human health. Pb(II) is a common pollutant among heavy metals found in industrial wastewater, and various methods were developed to remove the Pb(II). The adsorption method was more efficient, cheap, and eco-friendly to remove the Pb(II) from aqueous solutions. The removal efficiency depends on the process parameters (initial concentration, the adsorbent dosage of T-Fe3O4 nanocomposites, residence time, and adsorbent pH). The relationship between the process parameters and output is non-linear and complex. The purpose of the present study is to develop an artificial neural networks (ANN) model to estimate and analyze the relationship between Pb(II) removal and adsorption process parameters. The model was trained with the backpropagation algorithm. The model was validated with the unseen datasets. The correlation coefficient adj.R² values for total datasets is 0.991. The relationship between the parameters and Pb(II) removal was analyzed by sensitivity analysis and creating a virtual adsorption process. The study determined that the ANN modeling was a reliable tool for predicting and optimizing adsorption process parameters for maximum lead removal from aqueous solutions.

Experimental Design and Response Surface Methodology Applied to Graphene Oxide Reduction for Adsorption of Triazine Herbicides

In this work, pristine graphene oxide and its thermally reduced derivatives, rGO, were tested for the removal of triazines (atraton, prometryn, and atrazine) from water. The reduction process was optimized by means of design of experiments (DOE) coupled with response surface methodology (RSM), relying on the adsorption efficiency of the material. The optimal reduction conditions were calculated at a temperature of 110 °C maintained for 24 h; the mildest and simplest reduction protocol was chosen, as it allows in-air heat treatment with a common laboratory oven. The rGO samples were characterized before use, confirming a partial reduction process that, leaving intact most of the oxygenated functionalities on the graphene skeleton, may still allow favorable adsorption of pollutants through both hydrogen bonds and π-π interactions, which result from a large conjugated polyaromatic system. Triazine analyses were performed by high-performance liquid chromatography (HPLC); the data obtained from the adsorption isotherms were fitted with the Langmuir and Freundlich models, highlighting a slightly different adsorption behavior of atraton and prometryn compared with atrazine. Model outcomes were also used to support the hypotheses about the adsorption process.

Biosynthesized magnetite nanoparticles as an environmental opulence and sustainable wastewater treatment

This review emphasizes the win-win one-pot valorization process of different waste biomass that composed of many biological macromolecules (e.g. polysaccharides, polyphenols, carbohydrates, lipids, enzymes, proteins, etc.) and other biomolecules (e.g. alkaloids, terpenoids, tannins, phenolics, carotenoids, amino acids, sugars, vitamins, etc.) into biofunctionalized magnetite (Fe₃O₄) nanoparticles (BMNPs). It illustrates the sustainable recruitment of microbial intra- and extra-cellular metabolites, proteins, and/or enzymes in the biosynthesis of BMNPs. It elucidates the environmental affluence of such sustainable, cost-effective, and ecofriendly BMNPs as an antimicrobial agent for water disinfection, photo-degrader, and adsorbent for different xenobiotics, organic and inorganic water pollutants. It confers the future environmental aspects of BMNPs in biofuels production from lipids and lignocellulosic wastes, biosensors manufacturing and bio-upgrading of petroleum fractions, etc. It discusses the circular economy, challenges, and opportunities for scaling up the zero-waste green synthesis of MNPs. Nevertheless, imminent investigations are still needed to elucidate the exact rule of biological macro- and micro- molecules in BMNPs synthesis and mechanisms involved in its microbicidal and photodegradation activities. Accentuated researches are more required on the toxicity and/or biosafety of the green synthesized BMNPs to humans and other non-target organisms to ensure its eco-safety upon environmental applications.

Process modeling, characterization, optimization, and mechanisms of fluoride adsorption using magnetic agro-based adsorbent

In this study, fluoride removal from polluted potable water using magnetic carbon-based adsorbents derived from agricultural biomass was thoroughly investigated. An experimental matrix is designed considering the interactive effects of independent process variables (pH, adsorbent dose, contact time, and initial fluoride concentration) on the removal efficiency. Isotherms and kinetics studies, as well as anions interactions, were also investigated to understand the adsorption mechanisms further. The model parameters of isotherms and kinetics are estimated using nonlinear differential evolution optimization (DEO). Approaches like adaptive neuro-fuzzy inference system (ANFIS) and response surface methodology (RSM) are implemented to predict the fluoride removal and identify the optimal process values. The optimum removal efficiency of GAC-Fe₃O₄ (89.34%) was found to be higher than that of PAC-Fe₃O₄ (85.14%). Kinetics experiments indicated that they follow the intraparticle diffusion model, and adsorption isotherms indicated that they follow Langmuir and Freundlich models. Both PAC-Fe₃O₄ and GAC-Fe₃O₄ adsorbents have shown an adsorption capacity of 1.20 and 2.74 mg/g, respectively. The model predictions from ANFIS have a strong correlation with experimental results and superior to RSM predictions. The shape of the contours depicts the nonlinearity of the interactive effects and the mechanisms in the adsorption process.

Magnetic nanocomposites for sustainable water purification-a comprehensive review

Numerous contaminants in huge amounts are discharged to the environment from various anthropogenic activities. Waterbodies are one of the major receivers of these contaminants. The contaminated water can pose serious threats to humans and animals, by distrubing the ecosystem. In treating the contaminated water, adsorption processes have attained significant maturity due to lower cost, easy operation and environmental friendliness. The adsorption process uses various adsorbent materials and some of emerging adsorbent materials include carbon- and polymer-based magnetic nanocomposites. These hybrid magnetic nanocomposites have attained extensive applications in water treatment technologies due to their magnetic properties as well as combination of unique characteristics of organic and inorganic elements. Carbon- and polymer-related magnetic nanocomposites are more adapted materials for the removal of various kinds of contaminants from waterbodies. These nanocomposites can be produced via different approaches such as filling, pulse-laser irradiation, ball milling, and electro-spinning. This comprehensive review is compiled by reviewing published work of last the latest recent 3 years. The review article extensively focuses on different approaches for producing various carbon- and polymer-based magnetic nanocomposites, their merits and demerits and applications for sustainable water purification. More specifically, use of carbon- and polymer-based magnetic nanocomposites for removal of heavy metal ions and dyes is discussed in detail, critically analyzed and compared with other technologies. In addition, commercial viability in terms of regeneration of adsorbents is also reviewed. Furthermore, the future challenges and prospects in employing magnetic nanocomposites for contaminant removal from various water sources are presented.

Treatment of wood industry wastewater by combined coagulation-flocculation-decantation and fenton process

In the present research, the efficiency of turbidity and chemical oxygen demand (COD) reduction from the wood industry wastewater (WIW) by the use of a combined coagulation-flocculation-decantation (CFD) - Fenton process was studied. Firstly, the performance of three coagulants such as ferric chloride (FeCl₃ ), aluminum sulphate (alum), and polyaluminum chloride (PACl) was evaluated. The polyacrylamide (PAM) was used as a flocculant. The results showed that the polyaluminum chloride had a high removal efficiency. The COD reduction of 84.1% and turbidity removal of 82.0% of were obtained in coagulation-flocculation-decantation (CFD). Secondly, Fenton process was optimized, by the use of a response surface methodology (RSM), with application of a central composite design (CCD). The maximum turbidity and COD removal obtained by this process were 94.1% and 72.5% respectively, under optimal conditions ([Fe²⁺ ] = 250 mg/L, [H₂ O₂ ] = 500 mg/L, pH 3.5, time 60 min). The kinetics of COD and turbidity removal were determined by the model of first order. In conclusion, the combination of coagulation-flocculation-decantation (CFD) - Fenton process presented as a remarkable method for wood wastewater treatment. PRACTITIONER POINTS: A combination of coagulation-flocculation-decantation and Fenton process was introduced for the wood industry wastewater treatment. A designed experimental approach for treatment of wood industry wastewater using a Fenton process was studied. The yields of COD, BOD₅ , N-NO₃ , P-PO₄ , and dye removal were obtained according to the standard limits in Iran.

Process optimization and modeling of Pb(II) ions adsorption on chitosan-conjugated magnetite nano-biocomposite using response surface methodology

This study aimed to investigate the performance of a magnetic nano-biocomposite, chitosan conjugated magnetite nanoparticle (CH-MNP), for the removal of lead ions. The magnetite nanoparticles were synthesized through a controlled co-precipitation technique and were stabilized with citric acid. Subsequently, they were covalently bonded to chitosan via carbodiimide chemistry using EDAC/NHS activation. One of the notable advantages of this nano-biocomposite is its chemical conjugation, which does not have the weakness of the ultimate chitosan detachment of a physical bond and makes it an encouraging candidate for magnetic separation with no secondary waste production. The CH-MNPs had a diameter of ∼10 nm, with a saturation magnetization of 76.01 emu/g ensuring a superparamagnetic property. The response surface methodology (RSM) with a central composite design (CCD) framework was used for optimizing the adsorption process. The optimum conditions to achieve 92.15% of Pb(II) removal were found to be at a pH of 6.1 with the nano-adsorbent concentration of 1.04 g/L and a contact time of 59.92 min. Our adsorption isotherm data were fitted well with the Langmuir adsorption isotherm model, and the equilibrium data followed the pseudo-second-order kinetics and intraparticle diffusion kinetic model. The maximum Langmuir Pb(II) adsorption capacity was calculated to be 192.308 mg/g. These results suggest that the proposed synthetic nano-biocomposite is quite an ideal nano-adsorbent for Pb(II) removal in wastewater treatment technology.

Optimization and Experimental Design of the Pb2+ Adsorption Process on a Nano-Fe3O4-Based Adsorbent Using the Response Surface Methodology

Magnetic Fe3O4 nanoparticles have been used as adsorbents for the removal of heavy-metal ions. In this study, optimization of the Pb2+ adsorption process using Fe3O4 has been investigated. The adsorbent was characterized by various techniques such as transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDX), and Brunauer-Emmett-Teller (BET) analysis. The influence of process variables on adsorption of Pb2+ ions in accordance with p < 0.05 was investigated and analyzed by the Box-Behnken design (BBD) matrix with five variables (pH, adsorbent dose, initial Pb2+ ion concentration, contact time, and temperature). The pH and temperature were observed to be the most significant parameters that affected the Pb2+ ion adsorption capacity from the analysis of variance (ANOVA). Conduction of 46 experiments according to BBD and a subsequent analysis of variance (ANOVA) provide information in an empirical equation for the expected response. However, a quadratic correlation was established to calculate the optimum conditions, and it was found that the R 2 value (0.99) is in good agreement with adjusted R 2 (0.98). The optimum process value of variables obtained by numerical optimization corresponds to pH 6, an adsorbent dose of 10 mg, and an initial Pb2+ ion concentration of 110 mg L-1 in 40 min at 40 °C adsorption temperature. A maximum of 98.4% adsorption efficiency was achieved under optimum conditions. Furthermore, the presented model with an F value of 176.7 could adequately predict the response and give appropriate information to scale up the process.

Electro-Oxidation of Humic Acids Using Platinum Electrodes: An Experimental Approach and Kinetic Modelling

Humic acids (HA) are a potential hazard to aquatic ecosystems and human health. Because biological treatment of contaminated water does not satisfactorily remove these pollutants, novel approaches are under evaluation. This work explores electrochemical oxidation of HA in aqueous solution in a lab-scale apparatus using platinum-coated titanium electrodes. We evaluated the effects of HA concentration, current density, chloride concentration and ionic strength on the rate of HA oxidation. The initial reaction rate method was used for determining the rate law of HA degradation. The results showed that the reaction rate was first-order relative to HA concentration, chloride concentration and current density. An appreciable effect of ionic strength was also observed, most likely due to the polyanionic character of HA. We propose a kinetic model that satisfactorily fits the experimental data.

Continuous Adsorption Modeling and Fixed Bed Column Studies: Adsorption of Tannery Wastewater Pollutants Using Beach Sand

This study deals with the removal of residual pollutants from tanning wastewater by continuous adsorption mechanism, using local sand as a low-cost adsorbent. The possibility of pretreating a complex tannery effluent heavily loaded with a natural material such as sand is significant. The characterization of the adsorbent before and after continuous adsorption was performed by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Column studies were also carried out to evaluate the performance of the adsorbent and the efficiency of column adsorption. The adsorption kinetic rate seems to be strongly influenced by certain parameters such as the particle size of the material used, the withdrawal rate of the influent and the height of the adsorbent bed, and optimized parameters were found to be 63 μm, 15 ml·min−1, and 7 cm, respectively, and the color removal has achieved maximum values which vary between 95 and 100%. The results suggest that sand can be used as an economical adsorbent for the removal of color from the wastewater of the tanning industries.