Mercerized mesoporous date pit activated carbon-A novel adsorbent to sequester potentially toxic divalent heavy metals from water

Non-derivatizing solvent assisted waste-derived cellulose/ MOF composite porous matrix for efficient metal ion removal: comprehensive analysis of batch and continuous packed-bed column sorption studies

The use of metal-organic frameworks (MOFs) for wastewater treatment in continuous operation is a major challenge. To address this, the present study demonstrates the eco-friendly and economic synthesis of Ca-MOF immobilized cellulose beads (Ca-MOF-CB) derived from paper waste. The synthesized Ca-MOF-CB were characterized using standard analytical techniques. Batch sorption studies were performed to check the effect of cellulose composition (wt%), Ca-MOF loading, contact time, and initial metal ion (Pb2+, Cd2+, and Cu2+) concentration. Ca-MOF-CB beads exhibited outstanding equilibrium sorption capacities for Pb2+, Cd2+, and Cu2+, with estimated values of 281.22 ± 7.8, 104.01 ± 10.58, and 114.21 ± 9.68 mg g-1, respectively. Different non-linear isotherms and kinetic models were applied which confirmed the spontaneous, endothermic reactions for the physisorption of Pb2+, Cd2+, and Cu2+. Based on the highest equilibrium sorption capacity for Pb2+ ion, in-depth parametric column studies were conducted in an indigenously developed packed-bed column set-up. The effect of packed-bed height (10 and 20 cm), inlet flow rate (5 and 10 mL min-1), and inlet Pb2+ ion concentration (200, 300, and 500 mg L-1) were studied. The breakthrough curves obtained at different operating conditions were fitted with the empirical models viz. the bed depth service time (BDST), Yoon-Nelson, Thomas, and Yan to estimate the column design parameters. In order to determine the financial implications at large-scale industrial operations, an affordable synthesis cost of 1 kg of Ca-MOF-CB was estimated. Conclusively, the present study showed the feasibility of the developed Ca-MOF-CB for the continuous removal of metal ions at an industrial scale.

Tetraethylenepentamine-Grafted Amino Terephthalic Acid-Modified Activated Carbon as a Novel Adsorbent for Efficient Removal of Toxic Pb(II) from Water

In this study, a new composite, tetraethylenepentamine (TEPA), was incorporated into amino terephthalic acid-modified activated carbon (ATA@AC) through a one-pot integration of TEPA with the COOH moiety of ATA@AC. This process resulted in the creation of a TEPA@ATA@AC composite for Pb(II) removal from an aquatic environment. Several techniques, including SEM, EDX, FT-IR, TGA, XRD, and Zeta potential, were employed to emphasize the chemical composition, morphology, and thermal durability of the as-synthesized TEPA@ATA@AC composite. The impact of experimental variables on the adsorption of Pb(II) ions was studied using batch adsorption. The uptake assessment suggested that the TEPA@ATA@AC composite exhibited superior Pb(II) removal performance with high removal efficiency (97.65%) at pH = 6.5, dosage = 0.02 g, equilibrium time = 300 min, and temperature = 298 K. The isotherm data exhibited good conformity with the Langmuir isotherm model, whereas the kinetics data displayed strong agreement with both pseudo-first-order and pseudo-second-order kinetics models. This reflected that the Pb((II) uptake by the TEPA@ATA@AC composite was caused by physisorption coupled with limited chemisorption. The greatest monolayer uptake capacity of the TEPA@ATA@AC composite was 432.8 mg/g. The thermodynamic findings indicated that the Pb(II) uptake on the TEPA@ATA@AC composite was an exothermic and feasible process. After five adsorption-desorption runs, the TEPA@ATA@AC composite maintained a superior uptake capacity (83.80%). In summary, the TEPA@ATA@AC composite shows promise as a potent adsorbent for effectively removing Cr(VI) from contaminated water, with impressive removal efficiency.

Chitosan Polymer Functionalized-Activated Carbon/Montmorillonite Composite for the Potential Removal of Lead Ions from Wastewater

A simple approach for synthesizing a highly adsorbent composite was described for the uptake of heavy metal ions from wastewater. A simple approach for synthesizing a highly adsorbent composite was also described for the elimination of heavy metal ions from contaminated water. The nanocomposite was synthesized via a polymer grafting of chitosan on the activated carbon surface, followed by a stacking process with the layers of montmorillonite clay. The spectroscopic analyses were exploited to confirm the composite structure of the prepared materials. Various adsorption parameters, such as pH, initial concentration, and adsorption time, were assessed. The results showed that the adsorption capacity of the composite for Pb²⁺ ions increased as the pH increased until it reached pH 5.5. The maximum adsorption capacity was observed at an initial Pb²⁺ level of 20 mg/L and a contact time of 150 min. Kinetic models were evaluated, and the pseudo second-order model showed the best match. The adsorption isotherm data were processed by fitting the model with different isotherm behaviors, and the Langmuir isotherm was found to be the most suitable for the system. The maximum adsorption capacity for Pb²⁺ ion on the MMT/CS/AC composite was found to be 50 mg/g at pH 5.5. Furthermore, the composite maintained a high adsorption capability of 85% for five adsorption-desorption cycles. Overall, this composite is envisioned as an addition to the market of wastewater remediation technology due to its chemical structure, which provides influential functional groups for wastewater treatment.

Application of Bentonite Clay, Date Pit, and Chitosan Nanoparticles as Promising Adsorbents to Sequester Toxic Lead and Cadmium from Milk

Evaluating residual lead (Pb) and cadmium (Cd) levels in food products, especially milk, is critical for product safety and quality. In this purview, the current study aims to determine Pb and Cd concentrations in milk using atomic absorption spectrophotometry and compare their values with international standards. In addition, it aims to remove these metals from milk samples using low-cost, naturally occurring materials, such as bentonite, date pit, and chitosan nanoparticles. The ability of potential adsorbents was also investigated using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscope (TEM). Moreover, their impact on milk's nutritional properties was considered. The results revealed that most milk samples contained Pb and Cd, with mean values of 0.237 ± 0.179 and 0.041 ± 0.036 mg/kg, respectively. Furthermore, the three possible adsorbents demonstrated high sequestering ability due to their existing functional groups; the adsorption capacity of bentonite to Pb and Cd was 84 and 88%, date pit was 97 and 93%, and chitosan nanoparticles were 82 and 98%, respectively, with no discernible change in milk nutritional contents. In conclusion, the bentonite, date pit, and chitosan nanoparticles were found to be significantly effective and safe in removing hazardous trace elements (Pb and Cd) from contaminated milk.

Chitosan grafted tetracarboxylic functionalized magnetic nanoparticles for removal of Pb(II) from an aqueous environment

In this study, the chitosan-grafted tetracarboxylic functionalized magnetic nanoparticle (Fe₃O₄@TCA@CS) was synthesized via in situ co-precipitation process and amidation reaction to improve efficiency of adsorption process and obtain cost-effective adsorbents for removal of toxic Pb(II) metal from aqueous environment. The Fe₃O₄@TCA@CS nanocomposite was analyzed by FTIR, TEM-EDX, TGA, XRD, BET, and Zeta potential. The performance of Fe₃O₄@TCA@CS for Pb(II) ions adsorption was achieved as a function of pH, dose, contact time, initial Pb(II) concentration, and temperature. The influence of coexisting ions such as Na⁺, Ca²⁺, Mg²⁺, and Cd²⁺on removal efficiency of Pb(II) was also investigated. The results revealed that the coexisting ions had little influence on Pb(II) removal efficiency. The pseudo-first-order and Freundlich models were better to describe the adsorption of Pb(II) onto Fe₃O₄@TCA@CS and the maximum adsorption capacity of Pb(II) was 204.92 mg/g at pH:5.5; adsorbent dose: 0.015 g; and temperature: 298 K. Thermodynamic studies revealed that the Pb(II) adsorption onto Fe₃O₄@TCA@CS was an exothermic process. In conclusion, the study provides a new, simple, low-cost, and effective chitosan-based magnetic nanocomposite as a promising adsorbent with excellent adsorption capacity, magnetic separation, and reusability for Pb(II) removal from an aqueous environment.

Adsorption and recovery of lithium ions from groundwater using date pits impregnated with cellulose nanocrystals and ionic liquid

The study aims to prepare a novel low-cost and environmentally friendly adsorbent by using date pits (DP) impregnated with cellulose nanocrystals (CNCs) and ionic liquid (IL), named IL-CNC@DP. The batch adsorption of lithium onto IL-CNC@DP and DP were studied at different pH values, initial lithium concentrations, and temperatures. The thermodynamics constants of the adsorption process showed that the IL-CNC@DP was exothermic, did not favor a high level of disorder, and spontaneous in nature. At pH 6, there is a significant increase in the removal efficiency where it increased to 90%. This also could be explained by the fact that electrostatic attraction forces and hydrogen bonding existed between the protonated Li⁺ and the less protonated IL-CNC@DP adsorbent surface, which enhanced the percentage of Li⁺ removal. A strong inter- and intra-hydrogen bonding (O-H) stretching absorption is seen at 3311 cm^-1 that occurs in cellulose components. In conclusion, the IL-CNC@DP in comparison to the DP confirmed exceptional results proving that the modification enhanced the remediation of the Li⁺ from water. Furthermore, the selectivity of IL-CNC@DP towards real groundwater samples isolated in Qatar depends upon the physicochemical characteristics of each element.

Pristine biochar performance investigation to remove metals in primary and secondary treated municipal wastewater for groundwater recharge application

In this study, pristine biochar derived from date palm at 500°C was used in batch reactors (simulating blending adsorbent in aeration tank) and fixed-bed columns (simulating holding adsorbent in fixed-bed reactors). The removal performance of the biochar was assessed toward single and mixed-metal solutions as well as synthetic primary and secondary treated wastewater for copper (Cu2+), iron (Fe2+), nickel (Ni2+) and zinc (Zn2+). The order of maximum adsorption capacities of the metal ions at pH 7 followed: Fe2+ (2.92/2.94 mg/g)>Cu2+(2.69/2.78 mg/g) >Zn2+(2.03/2.19 mg/g)>Ni2+(1.69/1.02 mg/g) in single/mixed-metal solutions and Zn2+(2.91/11.26 mg/g)>Fe2+(0.60/5.29 mg/g)>Cu2+(0.56/5.05 mg/g)>Ni2+(0.13/2.02 mg/g) in synthetic primary/secondary treated wastewater. Blending biochar in aeration tank reduced metal concentrations. The metal ion concentrations in the final effluent were below the World Health Organization drinking water limits (2, 0.3, 0.1 and 3 mg/L for Cu2+, Fe2+, Ni2+ and Zn2+, respectively) suggesting that treated secondary wastewater can be spread into potable aquifers following disinfection. The Freundlich and the Pseudo-second order models fit best the batch experimental data. Experimental data from column analysis fit well to the Thomas model. The adsorption of metal ions on the surface of biochar was confirmed by Scanning electron microscopy, Energy dispersive X-ray studies, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy and X-ray diffraction. Desorption studies using different eluents demonstrated the reusability potential of the studied biochar.

Adsorptive batch and biological treatments of produced water: Recent progresses, challenges, and potentials

Produced water is responsible for the largest contribution in terms of waste stream volume associated with the production of oil and gas. Characterization of produced water is very crucial for the determination of its main components and constituents for optimal selection of the treatment method. This review aims to review and critically discuss various treatment options that can be considered cost-efficient and environmentally friendly for the removal of different pollutants from produced water. Great efforts and progresses were made in various treatment options, including batch adsorption processes, membrane filtration, advanced oxidation, biological systems, adsorption, coagulation, and combined processes. Chemical precipitation, membrane filtration, and adsorption have high removal efficiencies that can reach more than 90% for different produced water components. The most effective method among these methods is adsorption using different adsorbents media. In this review, date-pits activated carbons, microemulsions-modified date pits, and cellulose nanocrystals as low-cost adsorbents were thoroughly reviewed and discussed. Moreover, the potential of using biological treatments in the removal of various pollutants from produced water such as conventional activated sludge, sequential batch reactor, and fixed-film biological aerated filter reactors were systematically discussed. Generally, produced water can be utilized in various fields including habitat and wildlife, agricultural and irrigation sector, energy sector, fire control, industrial use also power regeneration. The degree of treatment will depend on the application that produced water is being reused in. For instance, to use produced water in oil and gas industries, water will require minimal treatment while for agricultural and drinking purposes high treatment level will be required. It can also be concluded that one specific technique cannot be recommended that will meet all requirements including environmental, reuse, and recycling for sustainable energy. This is because of various dominant factors including the type of field, platform type, chemical composition, geological location, and chemical composition of the production chemicals.

Valorisation of Pine Cone as an Efficient Biosorbent for the Removal of Pb(II), Cd(II), Cu(II), and Cr(VI)

Valorisation of pine cone as an efficient, low-cost, and eco-friendly biosorbent for the removal of heavy metals from aqueous solutions is evaluated. The morphology and surface chemistry of the biosorbent are characterized by scanning electron microscopy, energy-dispersive elemental analysis, and Fourier transform infrared spectroscopy, revealing the presence of carboxylic and alcoholic functional groups that interact with metal ions. The effect of the contact time, pH, amount of adsorbent, and initial metal concentration in the adsorption is studied, resulting in removal percentages for Cd(II), Cu(II), Pb(II), and Cr(VI) (metal concentration of 5 mg L-1) of 82.24%, 93.71%, 94.67%, and 88.8%, respectively ( $\text{pH}=5.4$ , 2 g L-1 of adsorbent), except for Cr(VI) ( $\text{pH}=2$ , 10 g L-1). The equilibrium data of Pb(II) and Cd(II) were found to follow the Langmuir-Freundlich model, with maximum adsorption capacities of 100.01 and 78.73 mg g-1, respectively, whereas Cu(II) followed the Langmuir model with 33.55 mg g-1. Cr(VI) adsorption data also fitted the Langmuir model, and the maximum adsorption capacity was 57.36 mg g-1. Adsorption data was obtained at pH 5.4 for divalent metal ions and at pH 2 for Cr(VI) and in a range of metal concentrations ranging from 1 to 500 mg L-1 at 298.2 K. The presence of the three metal ions in the solution does not affect the percentage of the target metal ion adsorbed, proving the absence of competition between them and showing the pine cone to be an efficient adsorbent to treat multimetal effluents allowing water reuse.

Synthesis, Characterization and Sorption Capacity Examination for a Novel Hydrogel Composite Based on Gellan Gum and Graphene Oxide (GG/GO)

A novel hydrogel composite based on gellan gum and graphene oxide (GG/GO) was synthesized, characterized and tested for sorption capacity in this work. The microstructural, thermogravimetric and spectroscopic analysis confirmed the formation of the GG/GO composite. Comparative batch sorption experiments revealed a sorption capacity of the GG/GO composite for Zn (II) ions of approximately 2.3 higher than that of pure GG. The GG/GO composite exhibits a maximum sorption capacity of 272.57 mg/g at a pH of Zn (II) initial solution of 6. Generally, the sorption capacity of the sorbents is approximately 1.5 higher in slightly acidic conditions (pH 6) comparative with that for strong acidic conditions (pH 3). The sorption isotherms revealed that the sorption followed a monolayer/homogenous behavior. The sorption kinetic data were well fitted by the pseudo-second-order kinetic model, and were consistent with those derived from sorption isotherms. The intraparticle diffusion was considered to be the rate-determining step. Two main sorption mechanisms for Zn (II) were identified namely, ion exchange at low pH values, and both ion exchange and chemisorption in weekly acidic conditions.

A comprehensive study on the bacterial biosorption of heavy metals: materials, performances, mechanisms, and mathematical modellings

Discharges of waste containing heavy metals (HMs) have been a challenging problem for years because of their adverse effects in the environment. This article provides a comprehensive review of recent findings on bacterial biosorption and their performances for sequestration of HMs. It highlights the significance of HM removal and presents a brief overview on bacterial functionality and biosorption technology. It also discusses the achievements towards utilisation of bacterial biomass with biosorption of HMs from aqueous solutions. This article includes different types of kinetic, equilibrium, and thermodynamic models used for HM treatments using different bacterial species, as well as biosorption mechanisms along with desorption of metal ions and regeneration of bacterial biosorbents. Its fast kinetics of metal biosorption and desorption, low operational cost, and no production of toxic by-products provide attraction to many researchers. Bacteria can easily be produced using inexpensive growth media or obtained as a by-product from industries. A systematic comparison of the literature for a metal-binding capacity of bacterial biomass under different conditions is provided here. The properties of the cell wall constituents such as peptidoglycan and the role of functional groups for metal sorption are presented on the basis of their biosorption potential. Many bacterial biosorbents as reported in scientific literature have a high biosorption capacity, where some are better than commercial adsorbents. Based on the reported results, it seems that most bacteria have the potential for industrial applications for detoxification of HMs.

Unary and binary adsorption studies of lead and malachite green onto a nanomagnetic copper ferrite/drumstick pod biomass composite

Modern-day practices are the major contributors in water quality deterioration, consequently results in clean water scarcity. Herein, co-precipitation procedure was adopted to develop a nanomagnetic copper ferrite/drumstick pod biomass (CuFe₂O₄/DC) composite, which was characterized, and optimized to sequester malachite green (MG) and lead (Pb(II)) in unary and binary systems from aqueous environment. Mesoporous CuFe₂O₄/DC surface with 16.96 m²/g BET surface area and acid functionalities predominance was observed. Under the studied experimental conditions, MG adsorption on CuFe₂O₄/DC in unary system was comparatively higher than that of Pb(II). MG and Pb(II) equilibrium results were fitted to Langmuir isotherm model, their respective maximum monolayer adsorption capacities at 328 K being 952.4 and 921.1 mg/g. On the other hand, binary system (in presence of MG) fastened Pb(II) adsorption kinetics and increased its uptake capacity. Additionally, humic acid (HA) matrix enhanced Pb(II) adsorption kinetics. Recovery studies showed maximal MG and Pb(II) elution with C₂H₅OH and 0.1 mol/L HCl, respectively. An 82.7% drop in Pb(II) adsorption was found after the first regeneration cycle, while only 17.6% fall in MG adsorption was witnessed after five consecutive regeneration cycles. Hence, it could be concluded that CuFe₂O₄/DC is a cost-effective and promising adsorbent for an efficient and rapid removal of Pb(II) and MG from both unary and binary systems.

Heteroatom-doped magnetic hydrochar to remove post-transition and transition metals from water: Synthesis, characterization, and adsorption studies

Efforts to improve water quality have led to the development of green and sustainable water treatment approaches. Herein, nitrogen-doped magnetized hydrochar (mSBHC-N) was synthesized, characterized, and used for the removal of post-transition and transition heavy metals, viz. Pb²⁺ and Cd²⁺ from aqueous environment. mSBHC-N was found to be mesoporous (BET surface area - 62.5 m²/g) and paramagnetic (saturation magnetization - 44 emu/g). Both, FT-IR (with peaks at 577, 1065, 1609 and 3440 cm^-1 corresponding to Fe - O stretching vibrations, C - N stretching, N - H in-plane deformation and stretching) and XPS analyses (with peaks at 284.4, 400, 530, 710 eV due to C 1s, N 1s, O 1s, and Fe 2p) confirmed the presence of oxygen and nitrogen containing functional groups on mSBHC-N. The adsorption of Pb²⁺ and Cd²⁺ was governed by oxygen and nitrogen functionalities through electrostatic and co-ordination forces. 75-80% of Pb²⁺ and Cd²⁺ adsorption at C_o: 25 mg/L, either from deionized water or humic acid solution was accomplished within 15 min. The data was fitted to pseudo-second-order kinetic and Langmuir isotherm models, with maximum monolayer adsorption capacities being 323 and 357 mg/g for Cd²⁺and Pb²⁺ at 318 K, respectively. Maximum Cd²⁺ (82.6%) and Pb²⁺ (78.7%) were eluted with 0.01 M HCl, simultaneously allowing minimum iron leaching (2.73%) from mSBHC-N. In conclusion, the study may provide a novel, economical, and clean route to utilize agro-waste, such as sugarcane bagasse (SB), for aquatic environment remediation.

Adsorptive removal of lead from acid mine drainage using cobalt-methylimidazolate framework as an adsorbent: kinetics, isotherm, and regeneration

In this work, cobalt-methylimidazolate framework has been used as an adsorbent in the removal of Pb(II) from acid mine drainage in adsorption batch system. X-ray diffraction, Fourier-transform infrared spectroscopy, Brunauer-Emmet-Teller and transmission electron microscope were used for structural, morphological, and surface characteristics of cobalt-methylimidazolate framework. The concentration of heavy metal ions in water samples was measured by inductively coupled plasma optical emission spectrometry. Different experimental factors/variables (such as contact time, dosage, and pH) affecting the adsorption of Pb(II) from acid mine drainage were optimized by response surface methodology based on central composite design. Under optimized experimental parameters, the maximum adsorption capacity of Pb(II) was found to be 105 mg g^-1. The nature of the adsorption process was investigated using Langmuir and Freundlich isotherm models. The obtained data best fitted Langmuir isotherm model suggesting a homogeneous adsorption process. Furthermore, the adsorption mechanism was investigated using five kinetic models, that is, pseudo-first order, pseudo-second order, intraparticle diffusion and Elovich model. The adsorption data fitted better to pseudo-second-order followed by intra-particle diffusion kinetic models suggesting that the adsorption mechanism is dominated by both chemical and physical adsorption processes. The adsorbent could be regenerated up to 8 cycles and it was successfully used in the removal of lead in real acid mine drainage samples.