Langmuir Sorption Capacity Research Articles

Solventless synthesis of bixbyite (Mn2O3) and hausmannite (Mn3O4) nanoparticles for ammonia nitrogen removal

Excessive accumulation of ammonia nitrogen (AN) in water resources poses serious health effects to humans, and control of its discharge in wastewater has been a primary global concern. Therefore, it has to be removed by robust, eco-friendly, and cost-effective approaches. In this study, Mn2O3 and Mn3O4 nanoparticles (NPs) were facilely synthesized by solid-state thermolysis, and characterized by XRD, FTIR, SEM, and TEM techniques. XRD results revealed the formation of single-phase cubic bixbyite, Mn2O3 and, tetragonal hausmannite, Mn3O4 nanoparticles exhibiting crystallite size of 27.69 and 19.38 nm, respectively. Morphological analysis shows the formation of agglomerated nanoparticles with varying shapes. The experimental isotherm results indicated that AN sorption by Mn2O3 could be well described by Freundlich model, indicating multilayer adsorption on heterogeneous surface. Contrarily, AN adsorption by Mn3O4 was consistent with the Langmuir model, representing a monolayer physisorption process on a homogeneous surface. The pseudo-first-order kinetic model fitted well to the experimental data than the pseudo-second order kinetic model. The Langmuir sorption capacities (qm) for Mn2O3 and Mn3O4 were 23.642 mg/g and 52.779 mg/g, respectively. Thermodynamic experimental kinetic data demonstrated that AN adsorption on the two forms of manganese oxides was an exothermic and spontaneous process. Regeneration experiments inferred that both Mn2O3 and Mn3O4 adsorbents could be reused.

Improving arsenic and cadmium contaminated paddy soil health and rice quality with plant-animal-based modified biochar: A mechanistic study

Arsenic and cadmium (As/Cd) are toxic elements which negatively impact the health and productivity of rice plants by subjecting them to stress. To address these issues, we developed three biochar amendment materials derived from plant-based corn-stover with iron-magnesium modification (FM@CB), char sourced from animal-based eggshells with iron-magnesium modification (FM@EB), and a blend (1:1, w/w) of both (FM@CEB). Batch adsorption experiment revealed that FM@CB exhibited a Langmuir sorption capacity of 77 mg g−1 for As(III) and 107 mg g−1 for Cd(II). In contrast, FM@EB showed values of 63 mg g−1 for As(III) and 115 mg g−1 for Cd(II), both observed in mixed systems. The exothermic dual adsorption mechanisms could include ion exchange, cation-anion bridging, complexation with surface functional groups, and precipitation processes. Pot trials were conducted, and the findings unveiled a substantial enhancement in rice grain yield with a 2% application of FM@CB, FM@EB, and FM@CEB. Specifically, there was a notable increase of 21.9%, 34.9%, and 37.6%, respectively. Simultaneously, the application led to a reduction in grain As levels by 34.4%, 53.2%, and 42.6%, and grain Cd levels by 48.7%, 71.2%, and 59.9%, respectively, in comparison to the no-amendment control condition. Our study observed a transformation in the soil's microbial community, as beneficial bacterial genera such as Anaeromyxobacter, Citrifermentans, and Desulfovibrio emerged to assist in the detoxification of these metal contaminants. Concurrently, the application of these materials led to a reduction in harmful bacterial genera like Pseudomonas, Flavobacterium, and Massilia. In addition, these amendments decreased the bioavailable As/Cd fractions in the soil and promoted the root-iron-plaque, which effectively sequesters these contaminants, rendering rice quality improvement. Ultimately, the use of these amendments, particularly FM@CEB, holds the promise of protecting rice from harmful metal(loid)s contaminants, increasing yields, and revitalizing the soil. The presence of these unique bacterial genera, especially those capable of detoxifying As/Cd, plays a crucial role in ensuring a healthier and more secure environment for all living organisms.

Evaluation of a pH- and time-dependent model for the sorption of heavy metal cations by poultry litter-derived biochar

Common isotherm and kinetic models cannot describe the pH-dependent sorption of heavy metal cations by biochar. In this paper, we evaluated a pH-dependent, equilibrium/kinetic model for describing the sorption of cadmium (Cd), copper (Cu), nickel (Ni), lead (Pb), and zinc (Zn) by poultry litter-derived biochar (PLB). We performed sorption experiments across a range of solution pH, initial metal concentration, and reaction time. The sorption of all five metals increased with increasing pH. For Cd, Cu, and Pb, kinetics experiments demonstrated that sorption rates were greater at pH 6.5 than at pH 4.5. For each metal, all sorption data were described using single set of four adjustable parameters. Sorption edge and isotherm data were well described with R2 > 0.93 in all cases. Time-dependent sorption was well described (R2 ≥ 0.90) for all metals except Pb (R2 = 0.77). We then used the best-fit model parameters to calculate linear distribution coefficients (KD) and equilibration times as a function of pH and initial solution concentration. These calculations provide a more robust way of characterizing biochar affinity for metal cations than Freundlich distribution coefficients or Langmuir sorption capacity. Because this model can characterize metal cation sorption by biochar across a wider range of reaction conditions than traditional isotherm or kinetic models, it is better suited for estimating metal cation/biochar interactions in engineered or natural systems.

Simultaneous and efficient removal of Cd(II) and As(III) by a magnesium-manganese codoped biochar composite: Sorption performance and governing mechanisms

As(III) and Cd(II) co-existence results in co-contamination in soil and water. It is still a great challenge for As(III) and Cd(II) simultaneous removal in the aqueous medium due to their contrasting chemical behaviour. Herein, we prepared a novel magnesium-manganese modified biochar composite (Mg/Mn@BC) for simultaneous Cd(II) and As(III) elimination from contaminated water. The synergistic effect of Mg/Mn@BC composite on synchronous Cd(II) and As(III) removal was confirmed. In the mixed sorption system, the Langmuir sorption capacity of Mg/Mn@BC for As(III) and Cd(II) was 164 and 316 mg g−1, respectively, which was more than that in the single adsorption system (75 and 295 mg g−1). In the single sorption system, the Mg/Mn@BC sorption efficiency was > 61% and 100% for As(III) and Cd(II), respectively, while > 87% and 100% in the mixed adsorption system. The characterization results revealed that synergistic adsorption was mainly attributed to anion-bridging (Mn/MgO–As–Cd) and cation-bridging (Mn/MgO–Cd–As). The ion exchange, precipitation, Cd–π binding and inner-sphere surface complexation with functional groups were predominant in the sorption process, while hydrogen bonding force and ternary complexation were the primary pathways in mixed adsorption system to eliminate Cd(II) and As(III). The results suggested that Mg/Mn@BC composite can be a potential material for wastewater treatment.

Synthesis of guar gum-g-coconut husk (SnO<SUB align="right">2-SiO<SUB align="right">2) nanocomposite for removal of Cu (II) and Cr (VI) from wastewater

A new sorbent material namely 'guar gum-g-coconut husk (SnO2-SiO2) [GG-g-CH(SnO2-SiO2)] nanocomposite' was synthesised by preparation of coconut husk metal oxide nanoparticles and grafted into acrylamide modified guar gum (GG) base with the help of crosslinking agent glutaraldehyde. Its adsorption capacity was evaluated for the adsorption of Cu (II) and Cr (VI) metal ions from wastewater and factors affecting variables such as pH, adsorbent dose, contact time, and concentration were extensively investigated. It was found from the study that the maximum percent removal achieved was 99% for Cu (II) and 92.74% Cr (VI) at a pH of 8.3 and 7.2 respectively with an optimum adsorbent dose of 250 mg/l in 120 mins. The sorption data obeyed both Langmuir and Freundlich isotherms but Freundlich isotherm was better mathematical fit than Langmuir model. The Langmuir sorption capacity (qmax) was found to be 105.26 and 98.03 mg/g for Cu (II) and Cr (VI) respectively. Freundlich constants, KF values obtained for Cu (II) was 1.135 and for Cr (VI) was 1.11 while 1/n values obtained for Cu (II) was 0.647 and for Cr (VI) was 0.656, respectively.

Elimination of amoxicillin by adsorption on coffee waste based activated carbon

In the present study, we describe the synthesis of coffee waste activated carbon (SAC) as potential material for the amoxicillin (AMOX) removal from aqueous solution. The conditions for synthesizing SAC were an impregnation weight ratio of raw biomass to KOH equal to 1:2 followed by activation at 800 °C for 1 h. The FTIR analysis and Boehm titration showed that SAC has 1.7627 and 1.5414 meq / g, respectively for acidic groups and of basic groups. The operating experimental parameters that govern the adsorption namely the temperature (288–318.16 K), intial pH (2.0–12.0), initial AMOX concentration Co (50–450 mg/L) and ionic strength were optimized. The adsorption isotherms were analyzed by various models. The experimental data were suitably matched to the Sips and Langmuir equations (R2 = 0.998). A Langmuir sorption capacity of 370 mg g−1 was determined, a value higher than that obtained on commercial activated carbon (CAC) employed for similarity purposes. The nature of the electrolyte was also examined with non-buffered AMOX solutions at different NaCl concentrations. The experimental results showed that AMOX adsorption is favored above pH 10. Otherwise, the absorption capacity is not influenced by the ionic strength of the electrolyte. The AMOX adsorption onto SAC was found to be exothermic and spontaneous under the operating parameters. The reusability of the adsorbent was tested by using appropriate chemical solvents and the results showed also that the sorption capacity decreases from 370 mg/g to 250 mg/g after four consecutive cycles.

Efficient removal of phenolic contaminants from wastewater samples using functionalized graphene oxide with thermo-sensitive polymer: Adsorption isotherms, kinetics, and thermodynamics studies

In this study, a facile strategy was reported for the first time to prepare 2-vinylpyridine/thermosensitive polymer functionalized graphene oxide to be applied as the nanoadsorbent for efficient removal of phenol and 2, 4-dichlorophenol compounds in the wastewater samples by ultra-performance liquid chromatography. Fourier-transform infrared spectroscopy, thermogravimetric analysis, carbon, hydrogen, and nitrogen elemental analysis, scanning electron microscope, and N2 adsorption-desorption isotherms characterized the functional groups and structures. Experimental factors including pH, contact time, temperature, amount of adsorbent dosage, and the initial concentration of phenol and 2, 4-dichlorophenol compounds were studied to optimize the removal procedure. The optimal conditions for phenol removal were recorded at pH=7, contact time of 10 min, the adsorbent dosage of 0.005 g, and temperature of 298 K. For 2, 4-dichlorophenol, the experimental conditions for the removal process were pH=8, the adsorbent dosage of 0.005 g, and contact time of 5 min at 298 K. The experimental results correlated well with the pseudo-second-order kinetics and suggested that the removal of phenol and 2, 4-dichlorophenol from an aqueous solution follows Langmuir isotherm model. The maximum Langmuir sorption capacity obtained was 333.33 and 103.092 mg g−1 at 298 K for phenol and 2, 4- dichlorophenol, respectively. Thermodynamic analysis indicated that the process was feasible and spontaneous (phenol: ΔG = -8.199 to -8.733 kJ mol−1 and 2, 4- dichlorophenol: ΔG = -14.796 to -15.069 kJ mol−1) and exothermic in nature (phenol: ΔH = -1821.51 J mol−1 and 2, 4- dichlorophenol: ΔH= -18325.7 J mol−1). The maximum removal efficiency of phenol and 2, 4-dichlorophenol compounds were 99% and 89%, respectively. Thus, the prepared nanoadsorbent can be used as an ideal adsorbent for the recycling removal of phenolic contaminants from wastewater samples.

Facile Preparation and Analytical Utility of ZnO/Date Palm Fiber Nanocomposites in Lead Removal from Environmental Water Samples.

This study reports a facile approach for preparing low-cost, eco-friendly nanocomposites of ZnO nanoparticles (NPs) and date palm tree fiber (DPF) as a biomass sorbent. The hypothesis of this research work is the formation of an outstanding adsorbent based on the date palm fiber and ZnO nanoparticles. ZnO NP/DPF nanocomposites were synthesized by mixing the synthesized ZnO NPs and DPF in different mass ratios and evaluating their efficacy in adsorbing Pb2+ from aqueous solutions. The structure and surface morphology of the developed ZnO NP/DPF nanocomposite were critically characterized by XRD, FESEM, and TEM techniques. Compared to ZnO NPs, the ZnO NP/DPF nanocomposites displayed significantly enhanced Pb2+ uptake. Pb2+ adsorption was confirmed via various isotherm and kinetic models and thermodynamics. The computed Langmuir sorption capacity ) was found to be 88.76 mg/g (R2 > 0.998), and the pseudo-second-order R2 > 0.999 model was most appropriate for describing Pb2+ adsorption. Impregnating the biomass with ZnO NPs enhanced the spontaneity of the process, and the value (−56.55 kJ/mol) of displayed the exothermic characteristics of Pb2+ retention. Only the loaded ZnO NP/DPF achieved the removal of a high percentage (84.92%) of Pb2+ from the environmental water sample (seawater). This finding suggests the use of ZnO NP/DPF nanocomposites for removing heavy metals from environmental water samples to purify the samples.

Novel metal based nanocomposite for rapid and efficient removal of lead from contaminated wastewater sorption kinetics, thermodynamics and mechanisms

A sol–gel method was utilized to prepare a novel nanocomposite adsorbent (nMgO/bentonite) and was tested for Pb(II) removal from aqueous solutions. The produced nanocomposite was investigated using, SEM–EDX, XRD, and FTIR analyses before and after Pb adsorption. Adsorption equilibrium and kinetic experiments were run in batch system under different conditions of pH, adsorbent dose, competitive cations, contact time and temperature. The results exhibited rapid Pb(II) adsorption by the nanocomposite in the first five min. Experimental lead adsorption equilibrium and kinetics data fitted well to Langmuir and power function models, respectively as indicated from the lowest standard error (SE) values. The calculated Langmuir maximum adsorption capacity (qmax) value of nanocomposite (75 mg g−1) was 4.5 times higher than that of bentonite (16.66 mg g−1). Moreover, the highest quantity of Pb(II) uptake was achieved at temperature of 307 K and pH 9. The Langmuir sorption capacity of the nanocomposite for Pb(II) increased from 75 to 145 mg g−1 with increasing temperature from 287 to 307 K. The thermodynamic parameters of Pb(II) adsorption by the nanocomposite affirm the spontaneous and endothermic nature of the adsorption process. Lead adsorption mechanisms by the nanocomposite were proposed and discussed.

Altering sorption and diffusion coefficients of gases in 6FDA‐based membrane via addition of functionalized Ti‐based fillers

AbstractIn this work, we systematically investigate and analyze the transport properties including carbon dioxide and methane gases, as well as carbon dioxide induced‐plasticization behavior over 6FDA‐based mixed matrix filled with nonfunctionalized and amine‐functionalized MIL‐125 (Ti) particles. First, the sorption behavior and permeability of CO2 and CH4 gases across the membranes were evaluated experimentally. Then, the dual‐mode sorption model was used to determine the gas solubility coefficients of gases, whereas the partial immobilization model was used to quantify the diffusivity coefficients of gases. From the results obtained, the permeability of CO2 and the ideal selectivity of CO2/CH4 increased 86%–118% upon the addition of nonfunctionalized and amine‐functionalized MIL‐125 (Ti) fillers into 6FDA/durene polymer. Such increment was mainly attributed to the altered sorption and diffusion properties of the membrane after incorporating the fillers that promoted the transport of CO2 through the membrane. The coefficients of Langmuir sorption capacity (C′H), Henry's law (KD), and affinity constant (b) obtained for NH2‐MIL‐125 (Ti)/6FDA‐durene increased 35.5%, 179.8%, and 104.4%, respectively, compared to pure 6FDA‐durene membrane. Besides, NH2‐MIL‐125 (Ti)/6FDA‐durene mixed matrix membrane showed the highest diffusivity coefficient of 35.1 × 10−8 cm2/s, resulting in higher CO2/CH4 selectivity of 37.1. In addition, the CO2 plasticization resistance obtained for nonfunctionalized and amine‐functionalized mixed matrix membrane was also improved about 150%–200% compared to pure 6FDA‐durene membrane. Overall, this study revealed that the inclusion of fillers into the polymer matrix has resulted in higher membrane performance than the neat membrane, which associated with the increased of both diffusivity and solubility of CO2. Thus, the incorporation of fillers into polymer matrix has altered the gas transport behavior, and this study could provide basic information on gas transport properties in analyzing the gas separation performance of 6FDA‐based mixed matrix membranes.

Pyrolyzed Ca-impregnated lignite for aqueous phosphate removal: Batch and column studies

Lignite is an abundant carbon material with a variable surface structure and low cation density The introduction of metal (hydr)oxide phases has improved the anionic binding potential of lignite. In this study, activated lignite (A−L), Ca2+−modified lignite (Ca−L), and Ca2+−modified activated lignite (Ca−A−L) were synthesized to remove aqueous phosphate. Lignite was first activated (KOH: lignite, mass ratio, 3:1) at 750 ºC to prepare A−L, improving its surface area by ~984-fold. Ca−L (27 wt% Ca) showed a large phosphate uptake (227.3 mg/g) (adsorbent dose 50 mg, 25 mL of 10–1500 ppm phosphate, 24 h, 25 °C, initial pH 6), due to the large amounts of micro-sized CaCO3, Ca(OH)2, and CaO particles in Ca−L. These particles actively precipitate phosphate/hydrophosphate as CaHPO4/Ca3(PO4)2. The breakthrough capacity of a 2.0 g Ca−L bed column (bed height 2.5 cm, diameter 1 cm) was 58.2 mg/g (flow rate 1.5 mL/min, 25 ºC, initial [PO43-] = 46.6 mg/L, particle size, 125–150 µm), ~4 fold lower than the maximum Langmuir sorption capacity. An interference study indicated that Ca−L is highly selective for phosphate. Spent Ca−L may improve soil fertility as it retains more phosphate species for later slow-release to the soil. Unit weight of phosphate can be removed by Ca−L more inexpensively than Norit ROW and Darco KB (two commercial activated carbon carbons). Precipitated Ca2+ phosphates/hydrophosphates in exhausted Ca−L can be recovered using HCl and Ca−L recycled. Moreover, low-cost lignite is a promising carbon support for the future synthesis of different value-added products.

Predicting phosphorus sorption isotherm parameters in soil using data of routine laboratory tests

Knowledge of phosphorus (P) sorption dynamics across different soil types could direct agronomic and environmental management of P. The objective of this study was to predict P isotherm parameters for a national soil population using data of routine laboratory tests. Langmuir and Freundlich sorption parameters were calculated from two different ranges (0–25 and 0–50 mg P L−1) using an archive of representative agricultural soil types from Ireland. Multiple linear regression (MLR) identified labile forms of aluminium (Al) and iron (Fe), organic matter (OM), cation exchange capacity (CEC), and clay as significant drivers. Langmuir and Freundlich sorption capacities, Freundlich affinity constant, and Langmuir buffer capacity were predicted reliably, with R2 of independent validation > 0.9. Sorption isotherm parameters were predicted from P sorbed at a single concentration of 50 mg P L−1 (S50). An MLR prediction of P sorption maximum in the 0–50 mg P L−1 range was achieved, to an accurate standard, using S50, OM, and Mehlich-3 Fe (R2 of independent calibration and validation being 0.91 and 0.95, respectively). Using Giles’ four shapes of isotherms (C, L, H, and S), L non-strict- and C-shaped isotherm curves accounted for 64% and 27% of the soils, respectively. Hierarchical clustering identified a separation of isotherm curves influenced by two ranges of Mehlich-3 Al. Soils with a low range of Mehlich-3 Al (2.5–698 mg kg−1) had no incidence of rapid sorption (C shape). Single point indices, Al, or available soil data make the regression approach a feasible way of predicting Langmuir parameters that could be included with standard agronomic soil P testing.

Removal of 3-chloroaniline from aqueous solution by treated coffee waste: isotherm modelling and thermodynamic studies

ABSTRACT 3-chloroaniline (3CA) concentrations were measured in aqueous solution by UV/Vis spectrophotometer. Validation of the calibration curve’s linearity, instrumental precision (RSD%), limits of detection and quantification were accomplished. The coefficient of calibration curve (1.0–10.0 mgL−1 3CA) had a high correlation (R2 = 0.9997) and the instrumental precision was in the range (RSD% = 0.50–0.74%, n = 10). The LOD and LOQ from the regression analysis were 0.20 mgL−1 and 0.61 mgL−1, respectively. A treated coffee waste adsorbent was utilised for 3-chloroaniline removal by process of sorption from aqueous solution. The major components of the coffee waste are the hemicellulose, cellulose, and lignin. The temperature effect (25°C, 35°C and 45°C) on sorption was evaluated, with sorption decreasing by increasing of temperature which reached 87%, 75% and 54%, respectively. Isotherms type L were found and associated with monolayer sorption. The parameters of sorption were examined by employing Langmuir, Freundlich and Dubinin-Radushkevich sorption models. The isotherm models of Langmuir and Dubinin-Radushkevich had acceptable correlation coefficients (R2 = 0.87–0.88). The Langmuir and Dubinin-Radushkevich sorption capacities of 3-chloroaniline were found to be 44 to 50 mgg−1. The values of separation factor (RL) were ranging from (0–1) which indicated a favourable sorption. In thermodynamic study the physical sorption process was confirmed by van’t Hoff equation. In addition, the free energy ∆G° (−19.1 kJmol−1) and enthalpy ∆H° (−56.6 kJmol−1) had negative values which suggested that the sorption was spontaneous, and the process was exothermic.

High capacity aqueous phosphate reclamation using Fe/Mg-layered double hydroxide (LDH) dispersed on biochar

Phosphate is a primary plant nutrient, serving integral role in environmental stability. Excessive phosphate in water causes eutrophication; hence, phosphate ions need to be harvested from soil nutrient levels and water and used efficiently. Fe-Mg (1:2) layered double hydroxides (LDH) were chemically co-precipitated and widely dispersed on a cheap, commercial Douglas fir biochar (695 m2/g surface area and 0.26 cm3/g pore volume) byproduct from syn gas production. This hybrid multiphase LDH dispersed on biochar (LDHBC) robustly adsorbed (~5h equilibrium) phosphate from aqueous solutions in exceptional sorption capacities and no pH dependence between pH 1–11. High phosphate Langmuir sorption capacities were found for both LDH (154 to 241 mg/g) and LDH-modified biochar (117 to 1589 mg/g). LDHBC was able to provide excellent sorption performance in the presence of nine competitive anion contaminants (CO32–, AsO43−, SeO42−, NO3–, Cr2O72−, Cl−, F−, SO42−, and MoO42−) and also upon remediating natural eutrophic water samples. Regeneration was demonstrated by stripping with aqueous 1 M NaOH. No dramatic performance drop was observed over 3 sorption-stripping cycles for low concentrations (5 ppm). The adsorbents and phosphate-laden adsorbents were characterized using Elemental analysis, BET, PZC, TGA, DSC, XRD, SEM, TEM, and XPS. The primary sorption mechanism is ion-exchange from low to moderate concentrations (10–500 ppm). Chemisorption and stoichiometric phosphate compound formation were also considered at higher phosphate concentrations (>500 ppm) and at 40 °C. This work advances the state of the art for environmentally friendly phosphate reclamation. These phosphate-laden adsorbents also have potential to be used as a slow-release phosphate fertilizer.

In-situ synthesised polyaniline - halloysite nanoclay composite sorbent for effective decontamination of nitrate from aqueous streams

ABSTRACT Nitrate (NO3 −) is one of the most common contaminants of water bodies with harmful effects to aquatic life and human beings. There is a need for development of sorbents for effective removal of NO3 − form aqueous streams. The aim of present study was to develop a Polyaniline modified halloysite nanoclay (PAni-HC) composite sorbent for the uptake of NO3 − from aqueous medium. Aniline coated on halloysite clay was oxidised in acidic medium at 4ºC to synthesise PAni-HC composite in one pot reaction. Successful incorporation of polyaniline (PAni) in the clay matrix was confirmed by different surface characterisation techniques. The as synthesised PAni-HC composite sorbent was tested for NO3 − sorption in a batch mode in the initial concentration range of 5–500 mg L−1. The analysis of NO3 − was performed using ion chromatography in the suppressed conductivity mode. The experimental data were assessed using different kinetic and equilibrium models for understanding the sorption behaviour of the PAni-HC composite. Sorption followed pseudo second order kinetics and intraparticle diffusion model. The maximum Langmuir sorption capacity of PAni-HC composite for NO3 − was found to be 27.9 mg g−1. The composite sorbent when treated with groundwater samples exhibited quantitative removal (> 90%) of NO3 −thus demonstrating the applicability of the sorbent in real situations.

Enhanced removal of zinc and cadmium from water using carboxymethyl cellulose-bridged chlorapatite nanoparticles

Zinc (Zn2+) and cadmium (Cd2+) in water pose serious threats to human health and the environment. In search for a more effective treatment technology, we prepared a type of carboxymethyl cellulose (CMC) bridged chlorapatite (CMC-CAP) nanoparticles and tested the material for removal of Zn2+ and Cd2+ from water. CMC macromolecules were attached to CAP by bidentate bridging and hydrogen bonding, preserving the high adsorption capacity of CAP nanoparticles while allowing for easy gravity-separation of the nanoparticles. CMC-CAP showed rapid adsorption kinetics and 22.8% and 11.2% higher equilibrium uptake for Zn2+ and Cd2+, respectively, than pristine CAP. An extended dual-mode isotherm model, which takes into account both sorption and chemical precipitation, provided the best fits to the sorption isotherms, giving a maximum Langmuir sorption capacity of 141.1 mg g−1 for Zn2+ and 150.2 mg g−1 for Cd2+ by CMC-CAP. Na+ at up to 5 mM showed modest effects on the uptake of the heavy metals, while 2–5 mM of Ca2+ exerted notable inhibitive effects. Dissolved organic matter (up to 5 mg L−1 as TOC) inhibited the Zn2+ uptake by 16.5% but enhanced the Cd2+ removal by 8.6%. Material characterizations and surface binding analyses revealed that ion exchange, surface precipitation, and surface complexation were the removal mechanisms for the heavy metals. This study demonstrates stabilizer bridging may serve as a convenient strategy to facilitate water treatment uses of nanoparticles.

Reduce graphene oxide-manganese oxide-black cumin based hybrid composite (rGO-MnO2/BC): A novel material for water remediation

Herein, the synthesis, characterization, and water treatment application of reduced graphene oxide-manganese oxide-black cumin hybrid composite, rGO-MnO2/BC, has been reported. The rGO-MnO2/BC was synthesized by incorporating MnO2 particles into reduced graphene oxide functionalized with functional groups of black cumin seeds. The prepared rGO-MnO2/BC was highly amorphous, having large numbers of functional sites, and was evaluated for adsorptive removal of arsenic and methylene blue from their respective aqueous solutions. Adsorption capacities of rGO-MnO2/BC for methylene blue and arsenite were evaluated in batch manner under optimum conditions. 1.0 g/L dosage of rGO-MnO2/BC could remove approximately 99 % of methylene blue and arsenite from initial concentration of 10.0 and 1.0 mg/L, respectively, after 75 min at 7.0 pH, and 27 °C temperature. The sorption data was evaluated to propose the adsorption mechanism by fitting into isotherm and kinetic models. The process of methylene blue and arsenite sorption was proved to be exothermic and feasible based on thermodynamic parameters. The Freundlich isotherm was most suitable for arsenite sorption and both Langmuir and Freundlich isotherms were suitable for methylene blue sorption data. The sorption kinetics followed pseudo-second order relationship for both adsorbates. The exploration of thermodynamics, isotherms, and kinetics parameters revealed physicochemical sorption mechanisms for both adsorbates onto rGO-MnO2/BC surface. The Langmuir sorption capacity of rGO-MnO2/BC for methylene blue and arsenite were found to be 232.5 and 14.7 mg/g, respectively, at 27 °C. The rGO-MnO2/BC is easy to prepare and is low-cost material, and showed high adsorption capacity as compared to the other reported adsorbents. Therefore, the application of rGO-MnO2/BC will be beneficial for upcoming research on water treatment technologies.

Adsorptive behaviour of surface tailored fungal biomass for the elimination of toxic dye from wastewater

ABSTRACT In the present research, adsorptive separation of Reactive Red-3 (RR3) from aqueous solution has been studied using surface tailored fungal biomass (Trichoderma harzianum). SEM with EDAX, XRD, FTIR and TG-DTA of the adsorbent had been discussed to verify the quality and efficiency of the adsorbent. The dye solution pH of 4, biosorbent dosage (0.5 g/L), contact time (150 min) and incubation temperature (40°C) for an initial dye concentration of 100 mg/L were predicted as an optimum condition for the highest removal of dye from aqueous solution. Among various kinetic models analysed, pseudo-second order model explains well the adsorptive cycle with a comprehensive relationship between experimental and measured biosorption capacity. Removal data was also analysed by using Langmuir, Dubinin–Radushkevich, Freundlich and Temkin isotherms. The process of biosorption was well described by Freundlich isotherm because of the higher correlation coefficient. The results of the models have been used to determine the ideal mechanism of the biosorption process. Langmuir sorption capacity was estimated as 172.63 mg/g at an optimum condition. Thermodynamic studies were also analysed to evaluate the parameters such as change in enthalpy (28.982 kJ/mol), change in Gibbs free energy and change in entropy (116.56 J/mol K), which indicates that the biosorption process was spontaneous at all temperatures and endothermic in nature. The prepared material can be an alternative to the existing biosorbents.

CH4 and CO2 sorption and diffusion carried out in various temperatures on hard coal samples of various degrees of coalification

The aim of the study was to analyse the effect of temperature on the sorption and diffusion of CO2 and CH4 on hard coal. Four coal samples, characterized by various degrees of coalification, were used in the research. The sorption measurements were carried out in three temperature values: 278 K, 313 K and 353 K and for the consecutive pressure values of 1 bar, 5 bar and 15 bar. Langmuir's sorption capacity in relation to CH4 and CO2 was the highest for the coal with the lowest degree of coalification and was 32.15 cm3/g and 76.4 cm3/g respectively. The lowest Langmuir sorption capacity in relation to CH4 and CO2 were obtained for medium-rank coal (19.23 cm3/g and 29.26 cm3/g) and high-rank coal (20.33 cm3/g and 32.89 cm3/g). The temperature growth resulted in a reduction of the sorption capacity of coal in relation to CH4 and CO2, and that decline was exponential in relation to temperature. The absolute decreases in the total sorption capacity were from 0.03 cm3/g to 0.21 cm3/g in relation to CH4, and from 0.10 cm3/g to 0.51 cm3/g in relation to CO2, per 1 K temperature increase. Within the measurement temperature range of 278–353 K, no „critical temperature point”, above which there is no reduction in CH4 and CO2 sorption, was observed. An increase in the temperature pushed up the values of the effective diffusion coefficients, in relation to CH4 by more than one order of magnitude, and in relation to CO2 by approximately four times. A decrease in the selectivity of CO2/CH4 was also observed along with the coal rank. The ratio of effective diffusion coefficient values DeCO2/DeCH4 for all the investigated coal samples declined strongly along with temperature growth.

Mechanisms for the removal of Cd(II) and Cu(II) from aqueous solution and mine water by biochars derived from agricultural wastes

The capacity of biochars derived from agricultural wastes to remove Cd(II) and Cu(II) from aqueous solution and contaminated mine water was evaluated using laboratory-based batch sorption experiments. To examine immobilization of heavy metals, biochars produced in a commercial-scale mobile pyrolizer from feedstocks: poultry litter; lucerne shoot; vetch shoot; canola shoot; wheat straws; and sugar-gum wood, were tested in a liquid-based system. Biochars were characterized by FTIR, XPS and XRD before and after the mine water treatment. Lucerne biochar had the highest Langmuir sorption capacity of Cd(II) (6.28 mg g−1) and vetch-derived biochar had the highest Cu(II) sorption capacity (18.0 mg g−1) at pH 5.5. All the biochars exhibited higher sorption capacity for Cu(II) than for Cd(II). The smaller ionic radius and higher electronegativity of Cu(II), and the PO43−, CO32− and N-containing functional groups of biochars enhanced their binding affinity. The results demonstrated that poultry litter-derived biochar was effective at removal of the Cd(II) and Cu(II) from mine water up to the levels recommended by the World Health Organisation. The results revealed that precipitation with CO32− and PO43−, complexation with –OH and –COOH groups and electrostatic interaction with O-containing surface functional groups were the main mechanisms involved in the removal of multi-metals by biochars, and that selection of feedstock materials for biochar production is important to maximise remediation of multi-metals in contaminated water.