Activation of Firmiana Simplex leaf and the enhanced Pb(II) adsorption performance: equilibrium and kinetic studies

Aging characteristics of degradable and non-biodegradable microplastics and their adsorption mechanism for sulfonamides

As emerging pollutants, microplastics (MPs) and antibiotics (ATs) became a research hotspot in recent years. To evaluate the carrier effect of degradable and non-biodegradable MPs in the aquatic environment, the adsorption behaviors of polyamide (PA) and polylactic acid (PLA) towards two sulfonamide antibiotics (SAs) were investigated. Both chemical and photo-aging were used to handle the virgin MPs. Compared with PA, PLA was aged more drastically, showing the obvious grooves, notches and folds. However, due to the higher temperature during chemical aging, the tiny KPLA (PLA aged by K2S2O8) particles were agglomerated and the specific surface area was reduced to nearly 95 %. For PA, the oxidation of chemical aging was stronger than photo-aging. After aging, the hydrophilicity and polarity of MPs increased. In the adsorption experiments, the adsorption capacity of PA towards SAs was 1.7 times higher than that of PLA. Aging process enabled the adsorption capacity of PLA increased 1.22-3.18 times. Overall, the adsorption capacity of sulfamethoxazole (SMX) by both MPs was superior to sulfamerazine (SMR). These results would help to understand the carrier effects and potential ecological risks of MPs towards co-existing contaminants.

New insights into adsorption mechanism of pristine and weathered polyamide microplastics towards hydrophilic organic compounds

The widespread coexistence of hydrophilic organic compounds and microplastics (MPs) in the environment has greatly increased their associated environmental problems. To evaluate the potential carrier effect of oxygen-containing MPs on coexisting pollutants, adsorption behaviors of four hydrophilic organic compounds (benzoic acid, sulfamethoxazole, sulfamerazine and ciprofloxacin) on MPs (pristine and weathered polyamide (PA)) were studied in the aquatic environment. The results showed that the surface morphology, size, oxygen content, molecular structure, surface charge and crystallinity of PA were changed after weathering, and the weathering degree of PA treated with heat-activated potassium persulfate was the highest. The main adsorption mechanisms included hydrogen bonding, hydrophobic interaction, charge-assisted hydrogen bonding, and electrostatic interaction. Hydrogen bonding and hydrophobic interaction contributed to the adsorption, while electrostatic interaction weakened the adsorption under the specific pH conditions. The formation of charge-assisted hydrogen bonding (CAHB) was also verified through pH influence experiments, and this force can overcome the electrostatic repulsion. The high adsorption of KPA (PA weathered by K₂S₂O₈) under alkaline conditions was well explained by the formation of homonuclear CAHB due to the increase of oxygen-containing functional groups compared to the other three PA. Additionally, weathering did not always enhance the adsorption of hydrophilic organic compounds on PA, which was related to the changes in surface charge, crystallinity and hydrophilicity of PA. Overall, the physical and chemical properties (e.g., specific surface area, oxygen content, molecular structure) of PA after weathering and its trend of adsorption were different from other oxygen-free MPs in this study. This work can provide basic data for environmental risk of MPs and contribute to clarify and understand the processes of oxygenated MPs in the aquatic environment.

Iron/titanium oxide-biochar (Fe2TiO5/BC): A versatile adsorbent/photocatalyst for aqueous Cr(VI), Pb2+, F- and methylene blue

This is the first report of the metal Fe-Ti oxide/biochar (Fe₂TiO₅/BC) composite for simultaneous removal of aqueous Pb²⁺, Cr⁶⁺, F^- and methylene blue (MB). Primary Fe₂TiO₅ nano particles and aggregates were dispersed on a high surface area Douglas fir BC (∼700 m²/g) by a simple chemical co-precipitation method using FeCl₃ and TiO(acac)₂ salts treated by base and heated to 80 °C. This was followed by calcination at 500 °C. This method previously was used without BC to make the neat mixed oxide Fe₂TiO₅, exhibiting a lower energy band gap than TiO₂. Adsorption of Cr(VI), Pb(II), fluoride, and MB on Fe₂TiO₅/BC was studied as a function of pH, equilibrium time, initial adsorbate concentration, and temperature. Adsorption isotherm studies were conducted at 5, 25, and 45 ℃ and kinetics for all four adsorbates followed the pseudo second order model. Maximum Langmuir adsorption capacities for Pb²⁺, Cr⁶⁺, F^- and MB at their initial pH values were 141 (pH 2), 200 (pH 5), 36 (pH 6) and 229 (pH 6) mg/g at 45 ℃ and 114, 180, 26 and 210 mg/g at 25 ℃, respectively. MB was removed from the water on Fe₂TiO₅/BC by synergistic adsorption and photocatalytic degradation at pH 3 and 6 under UV (365 nm) light irradiation. Cr⁶⁺, Pb²⁺, F^-, and MB each exhibited excellent removal capacities in the presence of eight different competitive ions in simulated water samples. The removal mechanisms on Fe₂TiO₅/BC and various competitive ion interactions were proposed. Some iron ion leaching at pH 3 catalyzed Photo-Fenton destruction of MB. Fe₂TiO₅, BC, and Fe₂TiO₅/BC bandgaps were studied to help understand photocatalysis of MB and to advance supported metal oxide photodegradation using smaller energy band gaps than the larger bandgap of TiO₂ for water treatment. A long range goal is to photocatalytically destroy some sorbates with adsorbents to avoid the need for regeneration steps.

Adsorption behaviors of the pristine and aged thermoplastic polyurethane microplastics in Cu(II)-OTC coexisting system

In this work, the hypothesis that thermoplastic polyurethane (TPU) microplastics (MPs) could form complex toxic pollution by absorbing both antibiotics and heavy metals simultaneously was proposed. The unique features of the adsorption of Cu(II) and oxytetracycline (OTC) on the pristine TPU and photo-aged (aged) TPU MPs in single and coexisting system were investigated, which included the kinetics, isothermal equilibrium and thermodynamics. The possibly synergistic or competitive effects between Cu(II) and OTC were also evaluated. The results showed that the adsorption process of Cu(II) and OTC could be described well by pseudo-second-order kinetic equation. The entire process could be divided into two stages: internal diffusion and external diffusion. The Sips model could give good fitting for the isothermal adsorption equilibrium. The thermodynamic parameters depicted the endothermic nature of adsorptions and the process was spontaneous. In the coexisting system, synergistic or competitive effects depended critically on the ratio of concentrations (Cu(II) vs OTC). When the ratio was 1:1, Cu(II) significantly enhanced the adsorption of OTC, while OTC showed a weak effect on Cu(II) adsorption. The synergies could be attributed to the formation of Cu(II)-OTC complex and the bridging effect of Cu(II). Overall, the adsorption capacity of aged TPU was higher than that of pristine TPU, which was due to the differences in morphological characteristics and functional groups. FTIR studies revealed that ester carbonyl and acylamino groups in the TPU may be involved in the adsorption of Cu(II) and OTC.

Carbonization and ball milling on the enhancement of Pb(II) adsorption by wheat straw: Competitive effects of ion exchange and precipitation

Straw biomass is a promising adsorbent for the removal of heavy metals. To improve its Pb(II) adsorption capacity and elucidate competition of adsorption mechanisms (e.g., ion exchange and precipitation), the Pb(II) adsorption mechanisms for wheat straw (WS-CK), wheat straw-biochar (WS-BC), and ball-milled wheat straw-biochar (WS-BC + BM) samples were investigated in detail by EDX, XRD, and FTIR. The results implied that the Pb(II) adsorption capacities at an adsorbent dosage of 0.2 g/L onto WS-CK, WS-BC, and WS-BC + BM were 46.33, 119.55, and 134.68 mg/g, respectively. This indicates that carbonization and ball milling are efficient techniques for improving the adsorption capacity of Pb(II) onto wheat straw, as WS-BC and WS-BC + BM exhibited adsorption capacities comparable to other commonly used bioadsorbents. Carbonization contributed significantly to precipitation (e.g., PbCO₃ and Pb₃(CO₃)₂(OH)₂). Furthermore, competition existed between ion exchange and precipitation during the Pb(II) adsorption process. With relative lower adsorbent dosages, carbonization and ball milling enhanced ion exchange capacity.

Removal of V (V) and Pb (II) by nanosized TiO2 and ZnO from aqueous solution

The removal of V (V) and Pb (II) by TiO₂ and ZnO nanoparticles from aqueous solution was studied with batch experiments. Atomic force microscopy (AFM), fourier Transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were used to characterize the surface properties including functional groups of the adsorbent as well as to explore adsorption mechanisms. Factors influencing V (V) and Pb (II) removal such as initial metal ion concentration and contact time were investigated. The kinetics of V (V) and Pb (II) removal occurred quickly and > 90% of the metals was removed within 30 min for both nanoparticles. Maximum adsorption of V (V) and Pb (II) onto TiO₂ and ZnO nanoparticles was observed at temperature of 298 K and pH 6.5 ± 0.1. The removal characteristics of the metals by the two nanoparticles were similar. A comparison of the kinetic models against experimental data showed that the kinetics react system was best described by the pseudo-second-order model. V (V) and Pb (II) reacted with functional groups, which led to the formation of polytype Pb-O bond and hydroxyl-vanadium complexes. The experimental data also confirmed the formation of heavy metal-OH sorption complexes on the adsorbent surfaces. This research enhanced current understanding of the removal of V (V) and Pb (II) by nanosized TiO₂ and ZnO from contaminated water.

HPLC-DAD-ESI-MS/MS analysis of fruits from Firmiana simplex (L.) and evaluation of their antioxidant and antigenotoxic properties

OBJECTIVES

The secondary metabolites of the fruits of Firmiana simplex (L.) were analysed by LC-DAD-ESI-MS/MS; furthermore, we evaluated their antioxidant and antigenotoxic properties.

METHODS

The antioxidant activity was investigated using the 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH), the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt (ABTS) and the ferric reducing antioxidant power (FRAP) assays. The antigenotoxic potential was determined via the comet assay.

KEY FINDINGS

The ethyl acetate fraction (EtOAc) was analysed by LC-DAD-ESI-MS/MS: phenolic acids and flavonoids were the main polyphenols of the fruits. The EtOAc fraction yielded the highest content of polyphenols with 314.61 mg GAE/g extract, followed by 297.51, 153.75, 101.47, 97.19 for dichloromethane, butanol, methanol and water extracts, respectively. As expected, a strong correlation exists between the antioxidant activity of the investigated extracts and their total phenolic content. In the DPPH assay, the IC₅₀ value of the most active EtOAc fraction was 6.79 μg/ml, relative to 2.92 μg/ml of the standard ascorbic acid. ABTS and FRAP assays supported the results of DPPH assay. Moreover, using the comet assay, we could show that the phenol-rich EtOAc extract exhibits an antigenotoxic potential in human liver cancer cells (Hep-G2) treated with hydrogen peroxide (H₂ O₂ ) as a genotoxic agent.

CONCLUSIONS

The fruits of Firmiana simplex may be a good natural source of antioxidant and antigenotoxic agents.

A New Neolignan Derivative, Balanophonin Isolated from Firmiana simplex Delays the Progress of Neuronal Cell Death by Inhibiting Microglial Activation

Excessive activation of microglia causes the continuous production of neurotoxic mediators, which further causes neuron degeneration. Therefore, inhibition of microglial activation is a possible target for the treatment of neurodegenerative disorders. Balanophonin, a natural neolignoid from Firmiana simplex, has been reported to have anti-inflammatory and anti-cancer effects. In this study, we aimed to evaluate the anti-neuroinflammatory effects and mechanism of balanophonin in lipopolysaccharide (LPS)-stimulated BV2 microglia cells. BV2 microglia cells were stimulated with LPS in the presence or absence of balanophonin. The results indicated that balanophonin reduced not only the LPS-mediated TLR4 activation but also the production of inflammatory mediators, such as nitric oxide (NO), prostaglandin E2 (PGE2), Interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α), in BV2 cells. Balanophonin also inhibited LPS-induced inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX2) protein expression and mitogen activated protein kinases (MAPKs), including extracellular signal-regulated kinase (ERK1/2), c-Jun N-terminal kinase (JNK), and p38 MAPK. Interestingly, it also inhibited neuronal cell death resulting from LPS-activated microglia by regulating cleaved caspase-3 and poly ADP ribose polymerase (PARP) cleavage in N2a cells. In conclusion, our data indicated that balanophonin may delay the progression of neuronal cell death by inhibiting microglial activation.

Removal of Pb, Zn, and Cd from contaminated soil by new washing agent from plant material

Soil washing is an effective approach to remove soil heavy metals, and the washing agent is generally regarded as one of the primary factors in the process, but there is still a lack of efficient and eco-friendly agents for this technique. Here, we showed that four plant washing agents-from water extracts of Coriaria nepalensis (CN), Clematis brevicaudata (CB), Pistacia weinmannifolia (PW), and Ricinus communis (RC)-could be feasible agents for the removal of soil lead (Pb), zinc (Zn), and cadmium (Cd). The metal removal efficiencies of the agents increased with their concentrations from 20 to 80 g L^-1, decreased with the increasing solution pH, and presented different trends with the reaction time increasing. CN among the four agents had the highest removal efficiencies of soil Pb (62.02%) and Zn (29.18%) but owned the relatively low Cd removal efficiencies (21.59%). The Fourier transform infrared spectroscopy showed that the abilities of plant washing agents for the removal of soil heavy metals may result from bioactive substances with specific functional groups such as -COOH, -NH₂, and -OH. Our study provided CN as the best washing agents for the remediation of contaminated soil by heavy metals.

Adsorption characteristics of Pb(II) from aqueous solutions onto a natural biosorbent, fallen arborvitae leaves

In this study, the potential of the oriental arborvitae leaves for the adsorption of Pb(II) from aqueous solutions was evaluated. Brunauer-Emmett-Teller analysis showed that the surface area of arborvitae leaves was 29.52 m(2)/g with pore diameter ranging from 2 to 50 nm. X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy showed C-C or C-H, C-O, and O-C=O were the main groups on the arborvitae leaves, which were the main sites for surface complexation. Finally, effects of adsorbent dose, initial pH, contact time, and coexisting natural organic matters (humic acid (HA)) on the adsorption of Pb(II) were investigated. The results indicated that the pHZPC (adsorbents with zero point charge at this pH) was 5.3 and the adsorption reached equilibrium in 120 min. Isotherm simulations revealed that the natural arborvitae leaves exhibit effective adsorption for Pb(II) in aqueous solution, giving adsorptive affinity and capacity in an order of 'no HA' > 5 mg/L HA > 10 mg/L HA, and according to the Langmuir models, the maximum adsorptions of Pb(II) were 43.67 mg/g, 38.61 mg/g and 35.97 mg/g, respectively. The results demonstrated that the oriental arborvitae leaves showed high potentials for the adsorption of Pb(II) from aqueous solutions.

Lead adsorption from aqueous solutions by a granular adsorbent prepared from phoenix tree leaves

In this study, a granular adsorbent was prepared from phoenix tree leaf powder with bentonite as the binder. The adsorption kinetics and isotherms of Pb²⁺ removal by the 500 °C-calcined granular adsorbent were studied by various models.

Partially hydrolyzed bamboo (Phyllostachys heterocycla) as a porous Bioadsorbent for the removal of Pb(II) from aqueous mixtures

A novel porous succinylated bioadsorbent was prepared by the partial enzymatic hydrolysis of bamboo (Phyllostachys heterocycla) and its subsequent modification with succinic anhydride. Pb(II) removal from solutions that also contained sodium chloride and an amino acid was investigated using the bioadsorbent. Enzymatic hydrolysis increased the number of accessible hydroxyl groups and surface area of the raw bamboo, and created many pores within the material. The porous succinylated bioadsorbent exhibited high efficiency for Pb(II) binding. The sodium chloride content significantly decreased the Pb(II) adsorption capacity, whereas a minor effect was observed in the presence of arginine. The experimental data could be accurately described by a pseudo-second-order kinetics model, and the adsorption proceeded via an ion exchange mechanism. Even in a solution containing sodium chloride and arginine, the maximum adsorption capacity of Pb(II) by the porous succinylated bioadsorbent was 99.5 mg/g at 303 K.

Application of grass char for Cd(II) treatment in column leaching test

Various adsorbents as well as toxicants have been investigated regarding the adsorption behaviors and mechanisms. However, most of these reports were based on batch test. The discrepancy in adsorption behaviors between batch test and column test has been recognized recently. This study was to investigate the sorption behavior of Cd(II) in a novel adsorbent made from Reed char. Batch adsorption test and column leaching test were both conducted. Various influence factors including confining pressure, pH, velocity, concentration and ionic strength were studied. The velocity was found to have negligible effect on the breakthrough of Cd(II). The adsorption affinity was observed for the first time to decrease from a high value (R(d) = 130.00) to a negligible one (R(d) = 1.20) with increasing confining pressure from 0 to 100.00 kPa. The breakthrough of acid Cd(II) solution was earlier for solutions with less pH and higher ionic strength. The Cd(II) laden adsorbent was reclaimed by flushing chelants through the column. The recycled adsorbent appeared to be applicable in the following adsorption treatment. Suggestions were provided regarding the potential engineering applications.

Cd(II) adsorption on various adsorbents obtained from charred biomaterials

Cadmium could cause severe toxicant impact to living beings and is especially mobile in the environment. Biomass is abundant and effective to adsorb heavy metals, but is easy to be decomposed biologically which affects the reliability of long-run application. Several biomasses were charred with and without additives at temperatures less than 200°C in this study. The prepared adsorbents were further testified to remove Cd(II) from aqueous solution. Equilibrium and kinetic studies were performed in batch conditions. The effect of several experimental parameters on the cadmium adsorption kinetics namely: contact time, initial cadmium concentration, sorbent dose, initial pH of solution and ionic strength was evaluated. Kinetic study confirmed (1) the rapid adsorption of Cd(II) on GC within 10 min and (2) the following gradual intraparticle diffusion inwards the sorbent at neutral pH and outwards at strong acidic solution. The grass char (GC) was selected for further test according to its high adsorption capacity (115.8 mg g(-1)) and affinity (Langmuir type isotherm). The Cd(II) removal efficiency was increased with increasing solution pH while the highest achieved at sorbent dosage 10.0 g L(-1). The ionic strength affects the sorption of Cd(II) on GC to a limited extent whereas calcium resulted in larger competition to the sorption sites than potassium. Spectroscopic investigation revealed the adsorption mechanisms between Cd(II) and surface functional groups involving amine, carboxyl and iron oxide. The long-term stability of the pyrolyzed grass char and the potential application in engineering practices were discussed.

Manganese removal from aqueous solution using a thermally decomposed leaf

As a significant agricultural and industrial raw material, Mn(II) has been intensively used and widely distributed in the environment. Recent studies indicate that Mn(II) could cause acute toxicity to aqueous livings and human beings. The treatment of Mn(II) contained wastewater is stringent for environmental preservations. This paper attempts to testify the performance of Mn(II) adsorption by a novel adsorbent, natural leaf that was partially decomposed at moderate temperature. The isothermal adsorption shows high prevalence for Mn(II) with adsorption capacity determined at 61-66 mg g(-1). Various factors including adsorbent dosage, pH, temperature and equilibration time were investigated regarding the effects on Mn(II) adsorption. It was shown that a rapid equilibration within 30 min could be achieved at pH values as low as 4.0 while an endothermic and spontaneous process could be disclosed with enthalpy change ranged from 13 to 0.78 kJ mol(-1) and the entropy change ranged from -35.79 to -11.58 kJ mol(-1) from 5 to 55 degrees C, separately. Spectroscopy study revealed chemisorptions relevant to phosphate, ferrous oxide and carbonate groups, and a physisorption on carbon black, which were main components of the adsorbent. No obvious linkage was observed between Mn(II) adsorption and the amine group which is critical to heavy metal adsorption in previous studies. The proposed preparation method and the basic guidelines regarding the adsorbents' selection seem promising in the engineering practices.

Removal of copper(II) ions by a biosorbent--Cinnamomum camphora leaves powder

In the present study, Cinnamomum camphora leaves powder (CLP) was investigated as a biosorbent for the removal of copper ions from aqueous solutions. The biosorbents before and after adsorption were measured by EDS and FT-IR. Kinetic data and sorption equilibrium isotherms were carried out in batch process. The adsorption kinetic experiments revealed that there are three stages in the whole adsorption process. It was found that Cu(II) adsorption onto CLP for different initial Cu(II) concentrations all followed pseudo-second order kinetics and were mainly controlled by the film diffusion mechanism. Batch equilibrium results at different temperatures suggest that Cu(II) adsorption onto CLP can be described perfectly with Langmuir isotherm model compared to Freundlich and D-R isotherm models, and the characteristic parameters for each adsorption isotherm were also determined. Thermodynamic parameters calculated show that the adsorption process has been found to be endothermic in nature. The analysis for the values of the mean free energies of adsorption (E(a)), the Gibbs free energy (DeltaG(0)) and the effect of ionic strength all demonstrate that the whole adsorption process is mainly dominated by ion-exchange mechanism, accompanied by a certain amount of surface complexation which has been verified by variations in EDS and FT-IR spectra and pH value before and after adsorption. Regeneration studies show CLP possesses an excellent reusability.