Elovich Kinetic Models Research Articles

Sorption potential of microplastics for azo- and phthalocyanine printing dyes

Synthetic printing dyes and microplastics (MPs) are ubiquitous pollutants in wastewater. This study aims to reveal the interactions between these contaminants when they interact in the natural environment. Five types of MPs (powdered polyethylene, granulated polyethylene, polyvinyl chloride, polyethylene terephthalate, and polypropylene) in combination with one phthalocyanine (Cyan) and one azo dye (Magenta) were subjected to adsorption tests in a synthetic aqueous matrix. The experimental parameters were dye concentration (1–200 mg/L), adsorbent mass (30 mg), experimental time (0–312 h), pH (7.3 ± 0.1) and temperature (25 °C). Both dyes are very well adsorbed on the studied polymers (qe = 273–581 mg/g) with polyvinil chloride showing the highest sorption capacity (581 mg/g for Cyan and 550 mg/g for Magenta). The experiment data fitted the Elovich kinetic model and Langmuir isotherm well, indicating monolayer chemisorption. Equilibrium was reached after 72–192 h. Electrostatic attraction, hydrogen bonds, π-π interactions, halogen bonding and van der Waals interactions, are an integral part of adsorption mechanisms of printing dyes on MPs. A model developed by the authors accurately predicted the sorption rate and capacity, implying a possible application to other printing dyes. The results of this research can serve as a basis for further research, such as wastewater treatment technologies for dye and microplastic removal and ecotoxicological studies.

Mandarin Biochar-TETA (MBT) prepared from Citrus reticulata peels for adsorption of Acid Yellow 11 dye from water

Dehydration technique with 80% sulfuric acid was used to create a novel biochar from mandarin peel wastes followed by condensate with triethylenetetramine (TETA) to give Mandarin Biochar-TETA (MBT). BJH, BET, FTIR, SEM, DSC, TGA, and EDX studies were used to characterise the MBT. The capacity of the newly developed biochar to remove Acid Yellow 11 (AY11) dye from a water solution was studied. The pH of AY11 dye adsorption was found to be best at pH 1.5. Using 100 ppm AY11 dye as a beginning concentration and 1.75 g L–1 MBT dose, the greatest percent of AY11 dye removal by MBT was 97.83%. The MBT calculated maximum adsorption capacity (Qm) was 384.62 mg g–1. Langmuir (LIM), Freundlich (FIM), Tempkin (TIM), and Dubinin–Radushkevich (DRIM) isotherm models were applied to analyse the experimental data. Furthermore, the results of these isotherm models were investigated by various known error function equations. The MBT experimental data was best suited by the LIM. Pseudo-first-order (PFO), pseudo-second-order (PSO), Elovich kinetic model (EKM), intraparticle diffusion (IPD), and film diffusion (FD) models were used to calculate kinetic data. A PSO rate model with a high correlation (R2 > 0.990) was used to assess the adsorption rate. The main mechanism of the MBT adsorption method of the AY11 dye’s anions adsorption is the electrostatic attractive forces that arise with the increase of positively charged sites in an acidic medium. The obtained data suggest that the prepared MBT adsorbent has the potential to be an effective material to remove the AY11 dye from water and that it may be used repeatedly without losing its adsorption efficiency.

Enhanced performance of functionalized MOF adsorbents for efficient removal of anthropogenic Hg(II) from water

Heavy metal pollution in water has been an increasing global environmental problem in recent years. At present, Zr-MOF-NAC has been successfully synthesized and used to efficiently capture mercury ions from wastewater. FESEM, XRD, FTIR and BET were applied for routine characterization. The best adsorption effect of Zr-MOF-NAC was obtained at pH = 5.0, and the maximum adsorption capacity was up to 644 mg/g. The adsorption kinetics and isotherms showed that the adsorption process was consistent with Elovich kinetic model and Temkin isotherm model. Chemisorption is the main adsorption behavior in the reaction process, and film diffusion is the limiting step of reaction rate. In addition, the adsorbent has excellent selectivity and reusability, and can selectively adsorb mercury ions in the solution containing interference ions. At the same time, after four adsorption-desorption experiments, the removal rate only decreased by 5%. The adsorption mechanism was revealed by XPS and other characterization methods, which mainly depended on electrostatic interaction and chelation, in which chemisorption was dominant, namely the interaction between the functional groups containing S, N and Hg(Ⅱ).

Biopolymeric Ni3S4/Ag2S/TiO2/Calcium Alginate Aerogel for the Decontamination of Pharmaceutical Drug and Microbial Pollutants from Wastewater.

The ubiquitous presence of pharmaceutical drugs and microbes in the water is leading to the development of drug resistant microbes. Therefore, efficient materials that can remove or inactivate the drug and microbe contaminants are required. In this work, nickel sulfide/calcium alginate (Ni3S4/CA), silver sulfide/calcium alginate (Ag2S/CA), modified titanium dioxide/calcium alginate (TiO2/CA), and Ni3S4/Ag2S/TiO2/calcium alginate (Ni3S4/Ag2S/TiO2/CA) aerogels have been synthesized for the removal of the oxytetracycline (OTC) drug and microbial contaminants from real beverage industry wastewater. The results revealed that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient for OTC adsorption and inactivation of microbes compared to Ni3S4/CA, Ag2S/CA and TiO2/CA aerogels. The OTC adsorption depends greatly on the solution pH, and optimum OTC removal was observed at pH 6 in its zwitterionic (OTC±) form. The formation of H-bonding and n-π electron donor-acceptors is possible to a considerable extent due to the presence of the double bond benzene ring, oxygen and nitrogen, sulfur-containing functional groups on the OTC molecules, and the Ni3S4/Ag2S/TiO2/CA aerogel. Based on the statistical analysis, root-mean-square deviation (RMSD), chi square (χ2) values, and higher correlation coefficient (R2) values, the Redlich–Peterson isotherm model and Elovich kinetic model are most suited to modelling the OTC adsorption onto Ni3S4/Ag2S/TiO2/CA. The prepared aerogels’ excellent antimicrobial activity is observed in the dark and with solar light irradiation. The zone of inhibition analysis revealed that the antimicrobial activity of the aerogels is in the following order: Ni3S4/Ag2S/TiO2/CA > TiO2/CA > Ag2S/CA > Ni3S4/CA, respectively. Moreover, the antimicrobial results demonstrated that reactive oxygen species, electrons, and active radical species are responsible for growth inhibition and killing of the microbes. These results indicated that Ni3S4/Ag2S/TiO2/CA aerogel is highly efficient in decontaminating pollutants from wastewater.

Evaluation of the use of adsorbents based on graphene oxide and cellulose for Cr(VI) adsorption

Water contamination is an environmental problem caused by the growth of the manufacturing industry. Among these contaminants, Cr ions, especially in their hexavalent form, can be highlighted. The objective of this study is to evaluate the capacity of graphene oxide (GO), cellulose aerogels, and GO-containing cellulose aerogels to remove hexavalent chromium (Cr(VI)) by adsorption. The aerogels were manufactured using a freeze-drying process, GO was synthesized using a modified Hummers’ method, and a batch adsorption system was used to verify the influence of the experimental factors. To interpret experimental data, Langmuir, Freundlich, Sips, Redlich–Peterson, Temkin isotherm, pseudo-first-order, pseudo-second-order, and Elovich kinetic models were used to interpret experimental data. The adsorbed amounts obtained were 274.52 mg.g−1 (GO), 199.89 mg.g−1 (cellulose aerogel), 237.42 mg.g−1 (0.5% GO aerogel), and 235.85 mg.g−1 (1% GO aerogel) at 25 °C. The data fit best to Langmuir and pseudo-second-order, indicating monolayer adsorption controlled by external and intraparticle diffusion. Additionally, thermodynamic parameters reflected spontaneous and exothermic adsorption. Furthermore, the adsorbents could be reused in more than 1 removal cycle, demonstrating the potential of using materials from renewable sources for Cr(VI) adsorption.

Step scheme nickel-aluminium layered double hydroxides/biochar heterostructure photocatalyst for synergistic adsorption and photodegradation of tetracycline

Improving the adsorption ability of layered double hydroxide (LDH) has been considered as a promising strategy to promote its photodegradation of aqueous pollutants. In this work, nickel-aluminium layered double hydroxides (NiAl-LDH)/biochar nanocomposites were prepared using a simple coprecipitation method, and then applied in synergistic adsorption-photodegradation of tetracycline (TC) in aqueous solutions. In addition, the governing TC removal mechanisms by the nanocomposites were revealed. All NiAl-LDH/BC samples showed strong adsorption and photodegradation of TC. The Langmuir maximum TC adsorption capacity of optimized NiAl-LDH/BC-0.5 reached 124.2 mg/g, which was much better than that of NiAl-LDH (56.1 mg/g) and biochar (11.1 mg/g). Besides, TC photodegradation rate constant of NiAl/BC-0.5 was 3.6 and 4.4 times of that of NiAl-LDH and BC, respectively. The NiAl/BC-0.5 exhibited the maximum TC adsorption-photodegradation efficiency 94.4% in 90 min compared to NiAl-LDH (73.7%) and BC (48.2%). The rate constant of modified Elovich kinetic model for synergistic adsorption and photodegradation on NiAl/BC-0.5 (9.477 min−1) was the highest among the composites. The NiAl-LDH/BC had significantly larger BET surface areas than NiAl-LDH and BC. The step scheme (S-scheme) heterostructures were constructed on the interface of BC and NiAl-LDH in nanocomposites, which facilitated the transfer of photo-induced charges. This work demonstrates that combination of NiAl-LDH and biochar can create synergy for TC adsorption-photodegradation, which is a promising and green strategy.

Adsorption and recovery of phosphate from aqueous solution by katoite: Performance and mechanism

Phosphate removal and recovery from wastewater is an effective approach to alleviate eutrophication and overcome the future scarcity of phosphorus. Katoite, a kind of calcium aluminate hydrate, was synthesized and examined as a novel adsorbent to remove phosphate from aqueous solution and recover phosphate as potential slow-release fertilizer. Batch experiments showed that the maximum phosphate adsorption capacity of katoite reached 111.51 mg P/g. Also, a high equilibrium adsorption capacity of 80.14 mg P/g was obtained at the initial concentration of 10 mg P/L. The adsorption could be well described by the Elovich kinetic model and Redlich-Peterson isotherm model. Thermodynamic study suggested that the adsorption was an endothermic process and occurred favorably and spontaneously. Moreover, the adsorption was almost independent of the ionic strength and showed high selectivity for phosphate in solutions containing common coexisting anions. The phosphate adsorption on katoite could be attributed to inner-sphere complexation and surface precipitation, which were further suggested by the SEM-EDS, FTIR and XPS analysis. Desorption experiments results indicated the possible plant availability and successive release property of the phosphate adsorbed on the surface of katoite. Overall, the study suggested that katoite is a promising candidate for phosphate adsorption and subsequent recovery as a slow-release phosphorus fertilizer.

Synthesis and characterization of a novel nanocomposite ([(SBA-15)-(Cu(BTC)]-[KZn(Fe(CN)6)]) for cesium removal from aqueous media and optimization condition using central composite design

This research aimed to remove cesium ions (Cs+) from aqueous solutions using a new synthetic nanocomposite [(SBA-15)-Cu(BTC)]-[KZn Fe(CN)6)]. To this end, a metal-organic framework [Cu(BTC)] was combined with silica (SBA-15) to improve its properties. This porous structure was employed as the support to immobilize [KZn(Fe(CN)6)] ion exchanger on its surface. The physical and chemical properties of the synthesized compounds were characterized. The response surface methodology (RSM) based on central composite design (CCD) was used to determine optimal operating conditions and interaction effects of the parameters influencing Cs adsorption. The optimal operating conditions were determined based on the ANOVA results (C = 200 mg/L, t = 1 h, T = 60 °C, and pH = 5.4). The kinetic and isotherm studies were carried out, and the thermodynamic properties of the system were investigated. The experimental kinetic data fitted well with the Elovich kinetic model. The Temkin isotherm suitably described equilibrium adsorption condition. The maximum equilibrium adsorption capacity was 115 mg g−1, and the experiment reached equilibrium whit in 1 h. The thermodynamic properties suggested that Cs adsorption was endothermic, spontaneous, and accompanied by an increase in the system's randomness. The presence of K+, Na+, and Sr2+ ions did not affect Cs adsorption. Finally, the experiments on adsorbent recovery showed that the adsorbent could be used with desirable results for three cycles. The eco-friendly nanocomposite presented in this research is suggested as an efficient adsorbent for Cs removal from aqueous solutions.

Adsorption of lead ions (Pb2+) from wastewater using effective nanocomposite GO/CMC/FeNPs: Kinetic, isotherm, and desorption studies

In this paper, we propose a new, effective, and easy-to-implement technology for hydrothermal synthesis of an adsorption material based on carboxymethylcellulose (CMC) and graphene oxide (GO) decorated with iron nanoparticles (FeNPs) for water purification from heavy metals. The purpose was to study the effect of the iron content in the materials on their physicochemical and adsorption properties. The synthesized materials were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy. Complex adsorption studies were performed using the example of lead ion removal from contaminated aqueous media. The influence of pH and contact time on the process efficiency was studied. The mechanism of adsorption was analyzed using pseudo first-order and pseudo second-order, intraparticle diffusion, and Elovich kinetics models. The results showed an optimal pH of 6 and contact time of 30 min. The process is best described by a pseudo second-order model. The material with a mass content of iron nanoparticles of 18% (CMC/GO + Fe 18 wt%) showed the largest adsorption capacity for Pb ions (1850 mg g−1). Adsorption isotherms of lead ions from aqueous media by the synthesized composite materials were studied using Dubinin–Radushkevich and BET models. The adsorption process is based on the chemical interaction of extracted ions with the surface of an adsorbent. Desorption studies showed the possibility of using the GO/CMC/FeNPs in real processes for purification of aqueous media. The obtained maximum value of adsorption capacity for the CMC/GO + Fe 18 wt% material was 1850 mg g−1, which is one of the highest in the literature for composite materials based on GO and vegetable raw material processing products.

Low-temperature aerobic carbonization and activation of cellulosic materials for Pb2+ removal in water source

Targeting the removal of Pb2+ in wastewater, cellulosic materials were carbonized in an aerobic environment and activated via ion exchange. The maximum adsorption capacity reached 243.5 mg/g on an MCC-derived adsorbent activated with sodium acetate. The modified porous properties improved the adsorption capacity. The capacity could be completely recovered five times through elution with EDTA. Because of the negative effects of Ni, Mg, and Ca elements, the adsorption capacities of activated carbonized natural materials were lower than that of pure cellulose. N2 adsorption measurement showed that the adsorbent had a large specific surface area as well as abundant micropores and 4-nm-sized mesopores. FTIR and surface potential results proved that carboxyl group was generated in the aerobic carbonization, and was deprotonated during ion exchange. This adsorbent consisted of C–C bonds as the building blocks and hydrophilic groups on the surface. XPS results demonstrated that the Pb 4f binding energies were reduced by 0.7–0.8 eV due to the interaction between Pb2+ and the activated adsorbent, indicating that the carboxylate groups bonded with Pb2+ through coordination interactions. Pseudo-second-order and Elovich kinetic models were well fitted with the adsorption processes on the pristine and activated carbonized adsorbents, indicative of chemisorption on heterogeneous surfaces. The Freundlich expression agreed well with the data measured, and the pristine and activated adsorbents had weak and strong affinities for Pb2+, respectively. The Pb2+ adsorption process was exothermic and spontaneous, and heat release determined the spontaneity. The adsorption capacity is attributed to the carboxylate groups and pores generated in the aerobic oxidation and ion exchange procedures.

Adsorptive removal of Cu(II) from aqueous solution by fermented sweet sorghum residues as a novel biosorbent

Sweet sorghum straw is a kind of natural wood cellulose with high porosity and high specific surface, which is theoretically conducive to the physical adsorption of heavy metal ions. In this paper, we reported a new biosorbent, the fermented sweet sorghum residues (FSSR), which is a byproduct of bioethanol production by fermentation of sweet sorghum straw, for the removal of Cu(II) from aqueous solution. The properties of the adsorption of Cu(II) on SSR and FSSR were studied and compared. The adsorption process of Cu(II) by SSR and FSSR conformed to the Elovich kinetic model. The isothermal adsorption process conformed to the Freundlich and the Tempkin models. The adsorption capacity of FSSR for Cu(II) was increased with the increase of pH. The adsorption mechanism of Cu(II) by FSSR was mainly attributed to ion exchange. SSR and FSSR were characterized by SEM-EDS, FTIR and XRD. The surface of FSSR had microporous structure, the content of –OH and other active functional groups increased. The fermentation has a certain destructive effect on the crystal structure of cellulose with the increase of amorphous structure. Therefore, fermentation process could be regarded as an effective means of microbial modification, to destroy the structure of the straw and result in the porous structure, which improved the adsorption capacity of SSR for heavy metals. FSSR could be used as a potential biosorbent for heavy metal removal from aqueous solution. Ethanol fermentation might be an effective method to improve performance of biosorbent for Cu adsorption.

Hypercrosslinked waste polymers as adsorbents for O2/N2 separation

Waste polymer materials offer a lot of promise for recycling or enhancement in terms of the environment. HCPs (hypercrosslinked polymers) are an excellent contender for recycling polymers in environmental applications. We employed waste-expanded polystyrene and waste polycarbonate as precursors to make HCPs adsorbents for O2/N2 adsorption. Characterization analysis were performed to determine the adsorbents' morphology and structure. The fine adsorbent was waste-expended polystyrene which had been synthesized at 45 °C for 12 h and had a surface area of 802.84 (m2/g), an average pore diameter of 2.86 nm, and a micropore volume of roughly 184.46 (cm3/g). The Sips isotherm and Elovich kinetic models provided the best agreement (R2 = 0.9994), according to experimental data. At 5 °C and 10 bar, the fine adsorbent had the highest O2 and N2 adsorption, with 12.78 and 7.67 (mmol/g), respectively. Eventually, the kinetic evidence demonstrated that the process physically occurred. Over nine cycles, the sorbent's ability for adsorption decreased by about 5%, indicating a high degree of reusability for air separation. The method described in this study can be considered a promising approach to air separation and purification by eco-friendly hypercrosslinked polymers.

Sequestration and toxicological assessment of emerging contaminants with polypyrrole modified carboxymethyl cellulose (CMC/PPY): Case of ibuprofen pharmaceutical drug

Ibuprofen (IBU) is a non-steroidal anti-inflammatory drug released into water bodies causing toxic biological effects on living organisms. The current study aims to eliminate IBU from aqueous solutions by a novel carboxymethylcellulose/polypyrrole (CMC/PPY) composite with high removal efficiency. Pyrrole was polymerized to polypyrrole whose average size was about 20 nm on the CMC surface. The maximum removal percentage of IBU by CMC/PPY composite was optimized at initial concentration 10 mg/L, dosage 0.02 g, and pH 7 with adsorption capacity of 72.30 (mg/g) and removal of 83.17 %. IBU adsorption onto CMC/PPY theoretically fits into the Langmuir isotherm and Elovich-kinetic models. Fish and Phytotoxicity assessment were performed with zebrafish and seeds of Vigna mungo (VM) and Vigna radiata (VR). The toxicity study reveals that before adsorption, IBU shows high toxicity towards the zebrafish mortality (33 %), growth inhibition (58.52 % for VM, 60.84 % for VR), and germination (86.66 % for VM and 90 % for VR). As CMC/PPY adsorbs IBU, toxicity drastically decreases. Before adsorption, LC50 was 233.02 mg/L. After adsorption, the LC50 increases to 2325.07 mg/L as IBU molecules get adsorbed by CMC/PPY. These findings show the feasibility of preparing CMC/PPY composite to effectively remove pharmaceutical pollutant IBU from aqueous solutions with their toxicological assessment.

Fabrication of α-MnO2/Fe-Mn binary oxide nanocomposite as an efficient adsorbent for the removal of methylene blue from wastewater

The development of the safe and cost-effective technologies for treating the dye-polluted wastewater has been a significant focus of researchers. In the light of this, α-MnO2/Fe-Mn binary oxide (α-MnO2/Fe-Mn BO) nanocomposite has been synthesized by a co-precipitation method. It was characterized by the FT-IR, XRD, BET, SEM, EDX, and TEM. The results indicated that the nanocomposite has a spheroid-like surface, a surface area of 92.954 m2/g and an average pore diameter of 2.39 nm. It was used as an adsorbent for the removal of methylene blue (MB) dye from an aqueous medium. The batch experiment revealed that 0.013 g of the nanocomposite can remove 98 % of MB (12.71 mg/L) in 30 min. The pH of the medium was the dominant factor in MB adsorption, where the highest removal efficiency was obtained at pH 4. Incorporation of sodium dodecyl sulfate (SDS) and NaCl decreased the MB adsorption. The adsorption process followed the pseudo-second-order and Elovich kinetic models. The results also fitted well with the Langmuir and Dubinin-Radushkevich (D-R) adsorption models. The maximum adsorption capacity was 89.63 mg/g at 30 °C and the nanocomposite showed good separation and regeneration properties. The removal efficiency decreased by about 20 % through five cycles. The α-MnO2/Fe-Mn BO is therefore considered a promising adsorbent for dyes owing to its high adsorption capacity, high chemical stability, good reusability, and simple synthesis procedure.

Experimental study on silica gel/ethanol adsorption characteristics for low-grade thermal driven adsorption refrigeration systems

• Silica gel/ethanol adsorption pair is promising for EVs and PV/T applications. • Ethanol is highly attracted to silica gel through chemical adsorption. • The silica gel/ethanol presents minor hysteresis owing to condensation. • The theoretical cyclic performance of silica gel/ethanol were calculated 0.97. There has been an increasing interest in adsorption cooling and heat pumps as the most feasible green alternative to the widespread vapor compression technology. Recent developments in adsorption cooling highlighted the need for cost-efficient adsorption pairs of advanced adsorption characteristics. In response, this article experimentally investigates and models silica gel/ethanol pair adsorption characteristics that can utilize low-temperature heat sources, such as those available in the emerging electric vehicles and PV/T systems. The investigated characteristics are the porous structure stability, isosteric heat of adsorption, adsorption diffusion energy, adsorption isotherm, and adsorption kinetic under extended operating conditions 15–55 °C. The results showed the high affinity of silica gel towards ethanol to provide sub-zero cooling. Silica gel showed no structure deterioration during the repetitive adsorption/desorption cycles of net 22 % cyclic ethanol uptake. The chemical adsorption of silica gel/ethanol showed a high level of adsorption/desorption reversibility with minimal hysteresis, which the Langmuir model best simulated. The heat of adsorption was determined to be 4.49 × 10 4 J/mol, which was higher than the diffusion energy of 1.80 × 10 4 J/mol due to the slow physical mobility of ethanol molecules inside silica gel pores. The Elovich kinetic model was the most suitable for simulating the chemical adsorption/desorption processes. The material level cyclic analysis showed the potential of 22 kJ/kg ads cooling effect and 0.97 coefficient of performance by utilizing a 55 °C heat source, widely available in PV/T systems and electric vehicles.

Adsorptive Removal of Lead and Chromate Ions from Water by Using Iron-Doped Granular Activated Carbon Obtained from Coconut Shells

In this study, a low-cost granular activated carbon doped with Fe2O3 nanoparticles (Fe–GAC) was prepared via a modified sol-gel technique and utilized for the elimination of lead (Pb(II)) and chromium (Cr(T)) ions from synthetic and actual brackish water. The effect of adsorption parameters on the removal of Pb(II) and Cr(T) ions from the water was evaluated in batch adsorption tests. The characterization results validated the distribution of well-defined Fe2O3 nanoparticles onto the GAC surface. GAC loaded with 5 wt.% of Fe2O3 (Fe–GAC 5) exhibited a maximum surface area of 848.2 m2 g−1. The equilibrium data of Cr(T) adsorption were in close agreement with the Langmuir and Sips models with R2 values of 0.95 and 0.96, respectively. However, the R2 values of the equilibrium data for Pb(II) adsorption were greater than 0.91 for all four models, i.e., Langmuir, and Sips, Freundlich and Redlich-Peterson. The maximum Langmuir adsorption capacities of Pb(II) and Cr(T) by Fe–GAC 5 at pH 5.6 and room temperature were 11.9 and 22.1 mg g−1, respectively. Pseudo-second order (R2Pb(II) = 0.99, R2Cr(T) = 0.99) and Elovich kinetic models (R2Pb(II) = 1, R2Cr(T) = 1) were found the most suitable for describing the adsorption kinetics data of Pb(II) and Cr(T) using Fe–GAC 5. The adsorption/desorption studies illustrated that the Fe–GAC is reusable and can be regenerated using 1.0 M HCl. Moreover, the Fe–GAC 5 was found effective to reduce heavy metals loading in actual brackish water to the allowed international standards of drinking water. Accordingly, the Fe–GAC could be a promising material for large-scale applications for the elimination of heavy metals from water.

Adsorption characteristics of antibiotics on microplastics: The effect of surface contamination with an anionic surfactant

Microplastics and antibiotics are common, typical pollutants, and they can cause compound pollution where they coexist in the environment. Surfactants in the environment can change the interface characteristics of pollutants, and then drive the change of environmental behavior of pollutants. In this paper, we studied the physicochemical properties of complexes of polystyrene (PS) and polyethylene (PE) contaminated with sodium dodecyl benzene sulfonate (SDBS); the complexes are referred to as SPS and SPE, respectively. Taking oxytetracycline (OTC) and norfloxacin (NOR) as representatives of broad-spectrum antibiotics, the effects of SDBS on the adsorption behavior of PS and PE were analyzed and possible mechanisms were proposed. The results showed that SDBS could effectively combine with PS and PE to enhance the surface electronegativity and reduce the Brunner–Emmett–Teller (BET) specific surface area and porosity. The crystal structure remained basically unchanged, and the surface functional groups changed slightly. SDBS greatly enhanced the saturated adsorption capacities of PS and PE for OTC and NOR, and made adsorption easier, which reduced the Gibbs free energy of the adsorption system. The adsorption behaviors of SPS and SPE for the two antibiotics were consistent with the Elovich kinetic model and Sips isothermal model. SDBS enhanced the hydrophilicity of the microplastics, which facilitated their adsorption of antibiotics dissolved in water. SDBS could directly combine with antibiotics to form a complex, further increasing the adsorption capacity of the microplastics for antibiotics. The –SO3H in SDBS could combine with oxygen-containing functional groups and –NH2 in OTC and NOR. Non-ionic covalent bonds, electrostatic interactions, and hydrophobic attraction between the alkyl chain and benzene ring also played a role in adsorption. SDBS made it possible for MPs to load more types and quantities of pollutants and change their preferential adsorption selectivity, which significantly aggravated the environmental hazards.

PH‐sensitive folic acid/poly(vinyl pyrrolidone) functionalized MnFe2O4/single‐walled carbon nanotubes for release of a natural anticancer agent: Chlorogenic acid

AbstractDespite promising features of chlorogenic acid (CGA) as an antioxidant and anticancer agent, short pharmacological half‐life constrains its application in cancer treatment. This work was aimed at developing a new nanocarrier with pH‐sensitive release behavior for CGA. In this direction, a porous nanohybrid, poly(vinyl pyrrolidone)/MnFe2O4/single‐walled carbon nanotube–folic acid (PVP/MnFe2O4/SWCNT–FA) was prepared by in situ coprecipitation of manganese and iron salts in the oxidized SWCNT suspension, followed by wrapping of PVP and then conjugating of FA on the magnetic SWCNTs. Afterward, the nanohybrid was loaded with CGA to form a carrier. The PVP/MnFe2O4/SWCNT–FA was characterized using Fourier transform infrared spectra, X‐ray diffraction, FE‐SEM/energy dispersive X‐Ray analysis spectroscope, TGA, and BET, confirming a well‐defined porous structure consisting of numerous functional groups. The CGA loading was carried out through the adsorption process. Adsorption equilibrium was reached within 60 min at pH 5.0. The experimental adsorption data showed an excellent nonlinear correlation coefficient with the simplified Elovich kinetic model and two‐step isotherm model. The CGA release was studied in simulated normal physiological fluid (pH 7.4) and simulated acidic tumor fluid (pH 5.6) over 6 h. The release rate from CGA loaded PVP/MnFe2O4/SWCNT–FA achieved 79.5% at pH 5.6, which was much higher than at pH 7.4 (37.2%), reflecting the acidic medium could markedly improve drug release. In addition, the Peppas–Sahlin model was more appropriate than the Higuchi and Korsmeyer–Peppas models to describe CGA release kinetics from the nanocarrier. In vitro cell viability studies indicated that PVP/MnFe2O4–SWCNT–FA had better biocompatibility in comparison with SWCNTs. Our findings indicate that the designed magnetic nanocarrier has acceptable performance to be used as a pH‐sensitive drug system with low toxicity for targeted drug delivery applications.

Crosslinked polyethylenimine/polyacrylonitrile blend membrane for multifunctional adsorption of heavy metals and endocrine disrupting chemicals in solution

A novel polyethylenimine/polyacrylonitrile blend membrane (PEI/PAN) was synthesized via crosslinking technology for removing multiple kinds of heavy metals and endocrine disrupting chemicals (EDCs) from aqueous solution including Cu(II), Cr(VI), bisphenol S (BPS), and 2,4-dichlorophenoxyacetic acid (2,4-D) in batch mode. Several characterization techniques were applied to identify the morphological and physicochemical characteristics of the synthesized PEI/PAN. The results show that the maximum adsorption capacities of Cu(II), Cr(VI), BPS, and 2,4-D reach up to 97.6, 136, 318, and 1303 mg/g at pH of 2.50, 4.89, 4.95 and 2.84, respectively, whereas the presence of salinity in the solution has affected the adsorption process. Moreover, the uptake of Cu(II) is more in line with Elovich kinetic model, and the kinetic processes for Cr(VI), BPS and 2,4-D can be described by the pseudo-first-order model. Freundlich model is more suitable for describing the adsorption isotherm behavior of PEI/PAN toward Cu(II) and Cr(VI), and Koble-Corrigan model can describe the adsorptive equilibrium processes for BPS and 2,4-D. Thermodynamic parameters are speculated that these adsorption processes are spontaneous and entropy-increasing, with endothermic processes for elimination of Cu(II), Cr(VI), and 2,4-D, while that of BPS is exothermic. PEI/PAN has possessed good reusability after five reuse cycles and has antibacterial property against gram-positive S. aureus. These adsorption processes may mainly occur due to the complexation for Cu(II), electrostatic force for Cr(VI), hydrogen bonding for BPS, as well as electrostatic attraction and hydrogen bonding for 2,4-D. Therefore, PEI/PAN membrane exhibits great potential to purify the wastewater polluted with heavy metals and EDCs.

Improved Adsorption of Tetracycline in Water by a Modified Caulis spatholobi Residue Biochar.

A potassium modified biochar (KBC) using Caulis spatholobi residue as the raw material was prepared by adopting a two-step method of pyrolysis followed by high-temperature potassium hydroxide activation, and its properties were characterized. Activation using potassium hydroxide under high temperature induced the loss of CaCO3 and partial C on biochar, which created a high specific surface area (1336.31 m2/g) together with a developed pore structure. pH displayed a slight influence on tetracycline adsorption, which signified the slight influence of the existence of tetracycline and the charge potential of biochar. Besides, pore filling, hydrogen bonding and π–π EDA stacking interactions possibly resulted in tetracycline adsorption on biochar. Tetracycline adsorption was fast in the original period, followed by a slower rate of adsorption until equilibrium was reached. Adsorption kinetics of tetracycline could be described using secondary and Elovich kinetic models. Adsorption isotherms for tetracycline were well fitted to the Langmuir isotherm model, and the maximum adsorption capacity of KBC was 830.78 mg/g at 318 K. According to a study of the thermodynamics, the adsorption of tetracycline on KBC was an endothermic reaction process. Corresponding results in the present study demonstrated that high-temperature potassium hydroxide activation enabled biochar to effectively eliminate tetracycline from water and wastewater.