HA Adsorption Research Articles

A UVA light-emitting diode microreactor for the photocatalytic degradation of humic acids and the control of disinfection by-products formation potential

Chlorination is one of the most applied technologies for drinking water disinfection. However, the generation of disinfection by-products (DBPs) in the chlorination process is threatening drinking water safety, especially when the concentration of natural organic matter (NOM) is high in source water. Climate change increases the fluctuation of NOM in source water, which further challenges water safety in small and rural communities. In this study, environmental microfluidics was introduced to a UVA-LED photocatalytic oxidation system for a rapid oxidation of NOM. The results showed that HA adsorption and degradation, and DOC degradation were more favored in low pH. At pH 5, 56.9% of HA and 58.1% of dissolved organic carbon (DOC) were removed in 3.4 min by the microreactor. DBP formation potential was efficiently reduced, with the highest reduction of THM and HAA formation potentials by 76% and 70.7%, respectively. Compared with the bottle reactor, the degradation rate constants of HA and DOC by UVA-LED microreactor were increased by 2.99 – 15.8 times, and 6.8 – 170.2 times, respectively. Homogenous irradiation and rapid mass transfer in the microreactor accelerated the inhibited oxidation of HA in acidic and base solutions and increased the apparent quantum yields of photocatalysis. Further, the microfluidic photocatalytic oxidation was much more efficient in the reduction of DPBs formation potential in a source water sample. The process was rapid and had low chemical and energy consumption. Approaches on system scale-up, system simplification, and energy conservation would increase potential of microfluidic photocatalytic oxidation in water purification for households and small communities.

Characteristics and mechanism of phosphate removal by lanthanum modified bentonite in the presence of dissolved organic matter

Lanthanum modified bentonite (LMB) is a widely used adsorbent for removing inorganic phosphorus from polluted water to prevent eutrophication. However, its efficiency can be affected by various environmental factors, including dissolved organic matter (DOM), which is still unclear. In this study, we systematically explored the influence of model DOMs, including HA, bovine serum albumin (BSA), and sodium alginate (SA), on phosphate adsorption by LMB, as well as to elucidate the underlying adsorption mechanisms. Our results showed that only HA had a significant effect on phosphate adsorption by LMB, causing inhibition. When three DOMs were mixed with phosphate in different proportions and DOM was mainly HA, the performance of phosphate adsorption on LMB became worse, while BSA can slightly offset this impact. The kinetics of HA and phosphate adsorption on LMB followed the pseudo-second-order kinetic model, and isotherms fitted the Langmuir model, with a maximum adsorption capacity of 5.7 mg g−1 for P and 12 mg g−1 for HA. However, when HA and phosphate were mixed based on their Qm, a C/P molar ratio of 5.35, LMB preferentially adsorbed phosphate. HA invasion was also disadvantageous for phosphate removal by LMB, in which P adsorption was less efficient at low-concentrations. However, during co-adsorption the adsorption capacity for HA was higher. With a secondary addition of higher levels of P, both pollutants were adsorbed more effectively. In the natural water experiment, phosphate concentration decreased with increasing shaking time, while the UV254 value showed a downward trend, indicating that LMB also adsorbed HA. Characterization results showed that La and phosphate formed LaPO4 precipitation, forming La–O–P inner-sphere complexes as the main mechanism of phosphate removal by LMB. La and HA formed La-HA complexes, with O–CO bonds from HA competing for lanthanum with phosphate. Despite HA obstructing pores from adsorbent, LMB still maintained a good binding ability with phosphate. It may form La–P-HA ternary complexes during adsorption to keep HA adsorption amount.

Adsorption of Tannic Acid and Macromolecular Humic/Fulvic Acid onto Polystyrene Microplastics: A Comparison Study

Dissolved organic matter (DOM) has been widely reported to influence the environmental behavior of microplastics (MPs), but little is known about the properties and mechanisms of interaction between specific DOM components and MPs. Here, we studied the adsorption of three representative DOM components (humic acid, HA; fulvic acid, FA; and tannic acid, TA) on polystyrene (PS) MPs in batch adsorption experiments. Results revealed that HA/FA adsorption was greater under acidic conditions, while higher TA adsorption on PS was found at pH 4 and 6. The divalent cation (Ca2+) exerted a more prominent role in enhancing HA, FA, and TA adsorption on PS than did monovalent ones (K+ and Na+). The adsorption process fitted well with the Freundlich isotherm model and the pseudo-second-order kinetics model. The adsorption site heterogeneity was evaluated using the site energy distribution analysis based on the Freundlich model. The greater binding ability of HA on the PS surface caused a more negatively charged surface than FA/TA, as reflected by Zeta potential values. The findings of this study not only provide valuable information about the adsorption behavior and interaction processes of various DOM components on PS MPs, but also aid our efforts to evaluate the environmental behaviors of MPs.

Mobility and Retention of Rare Earth Elements in Porous Media.

There is growing concern that rare earth elements (REEs) will become emerging soil–water contaminants because of their increased use in new technologies and products, which may lead to unavoidable release to the environment. To better understand the environmental behavior of REEs, a comprehensive set of adsorption and column transport experiments was conducted in quartz sand media. The retention and mobility of three representative REEs (La, Gd, and Er) were studied in the presence and absence of humic acid (HA; 5, 20, and 50 mg L–1) and under a range of pH conditions (5–8). Results show that REE mobility and retention are controlled by the amount of REE–HA complexes formed in a solution, which increases with increasing HA concentrations and solution pH. Gadolinium is the most mobile among the representative REEs, followed by Er and La, corresponding to the amount of (calculated) REE–HA complexes. Increasing HA concentrations in the REE solution inhibits REE retention in both the batch adsorption and column experiments. The same retardation trend was observed for lower HA concentrations (Gd > Er > La). In a fixed HA concentration, HA and REE adsorption decrease simultaneously as the solution pH increases, indicating the co-adsorption of REEs and HA on the sand. Scanning electron microscopy detection of elongated regions attached to the sand, where high REE and carbon (HA) concentrations were measured, further suggests the co-adsorption of REE–HA complexes. Modeling the column experiments shows that the time-dependent attachment is dominant at high HA concentrations, while at lower HA concentrations, both the time-dependent and spontaneous attachments play equal roles. These results provide a quantitative characterization of REE retention and mobility in sand media.

Black Water Purification by Activated Carbon from Ilalang Weeds (Imperata cylindrica) Adsorbent in Peatland Rural Area

The black water containing humic acid, HA in peat land rural area is a serious issue. This study aims to synthesis of activated carbon, AC from Ilalang Weeds, IW (Imperata cylindrica) as low-cost adsorbent for HA. The success AC synthesis by H3PO4 activator from IW was evidently characterized by Fourier Transform Infra-Red, FTIR and Scanning Electron Microscopy, SEM. The effects of pH solution, initial HA concentration, and contact time were systematically studied to investigate the performance of Activated Carbon from Ilalang Weeds, ACIW. The results showed the increasing of Langmuir monolayer capacity of HA adsorption on carbon from IW before (49.75 mg g-1) and after (56.82 mg g-1) activation process at the pH optimum 6.0. The equilibrium adsorption data fitted with the isotherm model was shifted from multilayer Freundlich model (CIW) into monolayer Langmuir model as the consequences of increasing pore diameter size and active sites intensity. Calculation of adsorption energy by Dubinin-Radushkevich (EDR) model, 0.50 and 2.24 kJ mol-1 for CIW and ACIW, respectively, showed the increasing of physical affinity of HA with the active sites of adsorbent. Adsorption kinetics showed that the adsorption behavior followed the Ho pseudo-second-order kinetic model. The experimental results of this work demonstrate that the ACIW can be used as a promising low-cost adsorbent for HA removal for clean water production in peat land rural area.Â

A Contrastive Study of Self-Assembly and Physical Blending Mechanism of TiO2 Blended Polyethersulfone Membranes for Enhanced Humic Acid Removal and Alleviation of Membrane Fouling.

In this study, membrane fabrication was achieved by two different methods: (i) self-assembly and (ii) physical blending of TiO2 in PES membrane for humic acid filtration. The TiO2 nanoparticles were self-assembled by using TBT as the precursor and pluronic F127 as triblock copolymers around the membrane pores. This was achieved by manipulating the hydrolysis and condensation reaction of TBT precursors during the non-solvent induced phase separation (NIPS) process. On the other hand, the TiO2 was physically blended as a comparison to the previous method. The characteristic of the membrane was analysed to explore the possibility of enhancing the membrane antifouling mechanism and the membrane flux. The membrane morphology, pore size, porosity, and contact angle were characterised. Both methods proved to be able to enhance the antifouling properties and flux performance. The HA rejection increased up to 95% with membrane flux 55.40 kg m−2 h−1. The rejection rate was not significantly improved for either method. However, the antifouling characteristic for the self-assembly TiO2/PES membrane was better than the physically blended membrane. This was found to be due to the high surface hydrophilicity of the MM membrane, which repelled the hydrophobic HA and consequently blocked the HA adsorption onto the surface.

Cd(II) and Pb(II) absorbed on humic acid-iron-pillared bentonite: Kinetics, thermodynamics and mechanism of adsorption

In this study, humic acid-iron-columnar bentonite (HA-Fe-PILC) obtained after HA adsorption on Fe-PILC was characterized by SEM, BET, XRD, zeta potential, FTIR, and XPS and reused for Cd(II) and Pb(II) removal from aqueous solution and mining wastewater through intermittent experiments. The characteristics results proved that the HA-Fe-PILC was successfully synthesized with a specific surface area and isoelectric point of 168.3 m2/g and 2.6, respectively. It contained HA of 31.26 mg/g and HA was stably combined with Fe-PILC under the solution pH value of 2−6. It mainly encompassed bonds of CO, Al-O, Si-O-Fe, and HOH. The adsorption of Cd(II) and Pb(II) ions increased with the increase of pH from 2 to 6 but decreased with the increasing ionic strength of NaCl in the solution. The adsorption process was endothermic and spontaneous in nature and fitted by the pseudo-second-order kinetic model and Langmuir model very well. The maximum adsorption capacities of Cd(II) and Pb(II) obtained by Langmuir model were 31.34 and 95.23 mg/g at the temperature of 25℃, respectively. The Cd(II) and Pb(II) concentrations in actual mine wastewater after treatment by HA-Fe-PILC could meet the wastewater discharge standard of China. The spent HA-Fe-PILC could be effectively regenerated by 1.0 mol/L HCl; after four regeneration, the Cd(II) and Pb(II) removal by HA-Fe-PILC remained at 60.2 % and 81.6 %. The Cd(II) and Pb(II) adsorption on HA-Fe-PILC was carried out by means of physical adsorption, ion exchange, chemical bonds, and surface complexation. Based on these results, the HA-Fe-PILC was an efficient and reusable adsorbent for Cd(II) and Pb(II) removal from wastewater. Overall, this study is a promising demonstration for the synthesis of a novel and reusable adsorbent for environmental applications, especially for the treatment of heavy metal in wastewater effluents.

Application of amine-functioned Fe3O4 nanoparticles with HPEI for effective humic acid removal from aqueous solution: Modeling and optimization

Humic acids are one type of natural organic matter and precursors of chloro organic compounds that cause a major problematic issue for water treatment plants. In the present study, Hyperbranched polyethylenimine (HPEI) was grafted onto Fe3O4 nanoparticles for HA adsorption from aqueous solution. Fe3O4@HPEI nanoparticles were characterized via TEM, SEM, FTIR, XRD, VSM, and BET analysis. The effects of various operational parameters including initial HA concentration, pH, adsorbent dose, contact time and ionic strength on the HA removal were assessed. According to the obtained statistical model, the optimal condition was acquired at the initial HA concentration 79 mg/L, adsorbent dose 0.128 g/L, pH 3 and contact time 29 min, which up to 97.27% HA were adsorbed by Fe3O4@HPEI that was close to the predicted result by the model (95.6%) that confirmed the validity of the selected model. The adsorption data were fitted to the pseudo-second-order kinetic and Freundlich isotherm. Thermodynamic parameters indicated that the adsorption process was spontaneous and endothermic. The fabricated Fe3O4@HPEI nanoparticles could be repeatedly utilized as a suitable adsorbent to remove HA from the aqueous environment.

Adsorption of HA (humic acid) using sulfuric acid-crosslinked chitosan/pectin polyelectrolyte complex film

A sulphuric acid-crosslinked chitosan/PEC film had been synthesized and applied for adsorption of HA from aqueous solution. The parameters for adsorption study were an optimum ratio of chitosan/pectin composition, contact time, the effect of the solution pH, and HA concentration. The model for adsorption kinetics and isotherm adsorption as well as desorption study were also conducted. The result showed that the film was durable in water at pH 2 to 12. The analysis using FTIR indicated a shift of absorption peak at 1527 cm−1 (bending vibration N−H in −NH3+). Analysis with SEM showed the morphological differences of the film before and after adsorption and after desorption. Adsorption reached its optimum capacity in the film with a ratio of chitosan and pectin composition 70:30, at pH 6, contact time of 480 mins and HA concentration of 450 mg L−1. The kinetic model of HA adsorption could be explained by the second-order kinetic model of Ho & McKay and the adsorption isotherm follows the Langmuir isotherm model with a maximum adsorption capacity of 50.0 mg g−1, the Langmuir constant (KL) of 1.49×105 L mol−1 and the adsorption energy was found to be 29.7 kJ mol−1. The highest desorption was 82.5% using 1 M NaOH.

Removal of natural organic matter from water using chemically activated coffee husk

The presence of natural organic matter (NOM) in source water has posed many challenges for conventional water treatment facilities. Small organic acids, such as humic acid, present in NOM, have a high potential to influence the performance of water treatment processes. Uncontrolled application of agricultural chemicals leads to the simultaneous presence of toxic substances. In this work, batch adsorption experiments were conducted to examine the biosorption of HA onto chemically activated coffee husk. The biosorption process was studied as a function of operating conditions, such as contact time, pH of the solution, HA concentration, adsorbent dose and agitation speed parameters. Experimental results showed that the adsorption has an equilibrium time of 60 min with a maximum adsorption of 93.7%. The optimum pH for maximum HA adsorption was found to be 5.5, with a maximum adsorption of 94.3%. . As the dose of adsorbent increased from 1 to 25 g/L, the concentration of HA was observed to reduce from 10 to 1.67 mg/L which is below the WHO (World Health Organization) guideline value of 2 mg/L. The amount of HA adsorbed increased with increasing the initial adsorbent concentration from 0.5 to 20 mg/L. The adsorption kinetics well fitted the pseudo-second order model with the correlation coefficient R2 = 0.997 and Ks = 0.078. The experimental sorption equilibrium can be represented by the Langmuir isotherm (R2 = 0.998, SSE = 0.006). An average desorption capacity of 87.3% was observed. The study shows that chemically activated coffee husk can be a potential candidate to be used as a biosorbent in the removal of NOM from aqueous solutions.

Adsorption of Soil-Derived Humic Acid by Seven Clay Minerals: A Systematic Study

AbstractHumic acid (HA)-clay complexes are well known for their contribution to soil structure and environmental processes. Despite extensive research, the mechanisms governing HA adsorption are yet to be resolved. A systematic study was conducted to characterize the adsorption of a soil-derived HA to seven clay minerals. Clay surfaces affected HA adsorption directly due to structural differences and indirectly by altering solution pH. The following order of HA removal was obtained for the clay minerals at their natural pH: illite ≫ palygorskite > kaolinite > sepiolite > montmorillonite = hectorite ≫ talc. Removal of HA (precipitation and adsorption) by kaolinite and illite was attributed to the low pH they induce, resulting in protonation of the clay and HA surfaces. In spite of the low pH, the zeta potential for HA remained negative, which promoted HA adsorption to the protonated clay surfaces by ligand exchange. Ionic strength did not affect HA adsorption to clay minerals with low zeta potentials, indicating that charge screening is not a major mechanism of HA adsorption for these minerals, and supporting the suggestion that ligand exchange is the main adsorption mechanism to pH-dependent sites. The increase in ionic strength did, however, promote HA adsorption to clay minerals with high zeta potentials. At pH 8–9 the order of HA affinity for clay minerals was: palygorskite >>sepiolite > montmorillonite = hectorite > kaolinite > illite > talc, emphasizing strong HA interactions with the fibrous clays. This strong affinity was attributed to their large surface areas and to strong interactions with OH groups on these clay surfaces. Results indicated that HA did not enter the intracrystalline channels of the fibrous clays but suggested that their macro-fiber structure facilitates HA adsorption. The sorption of HA to kaolinite further increased in the presence of Cu2+, and the sorption of Cu2+ increased in the presence of HA, due to a number of synergistic effects. This study emphasizes the diverse effects of clay structure and solution chemistry on HA adsorption.

Leaching mechanisms of constituents from fly ash under the influence of humic acid

As a low-cost material for adsorption, FA is one of the most efficient adsorbents of HA. However, the leaching of elements from FA is problematic during utilization in water treatment. In this investigation, the potential leaching behaviors of Calcium, Arsenic, Born, Chromium, and other elements from FA in HA solution were studied via batch test. The data show that HA had an effect on the leaching of each element of FA, depending on the pH, the initial concentration of HA and the addition of calcium oxide (CaO). The Langmuir isotherm could better fit the equilibrium data in different initial concentrations of HA from 10 to 100mg/L. Because of the interaction between HA and the FA leaching elements, multi-layer adsorption occurred when the initial concentration of HA was more than 100mg/L. The pH and free CaO content played major roles in HA adsorption and FA leaching. Using SEM and XRD to characterize the solid of FA being mixed with CaO treated in solution, the results demonstrated that the reaction between FA and CaO could generate crystal minerals, such as portlandite, gismondine, ettringite (AFt) and calcite, which effectively restrained the leaching of elements, reduced secondary pollution.

Humic Acid Removal by Combining the Magnetic Property of Maghemite with the Adsorption Property of Nanosized Hydroxyapatite

Maghemite incorporated hydroxyapatite (HAP) nanocomposite was prepared by in situ precipitation of the calcium phosphate phase in an iron oxide colloidal suspension. The resultant nanocomposite was characterized by x-ray diffraction, Fourier transform infrared spectrometer, transmission electron microscope, N2 adsorption analysis, and vibrating sample magnetometry. The potential of HAP/γ-Fe2O3 nanocomposite for HA adsorption from aqueous solution was evaluated by batch experiments and adsorption kinetic tests. HA adsorption amount on the adsorbent decreased with increasing solution pH and the presence of KNO3 and alkali-earth metal ions resulted in enhanced HA adsorption. HA adsorption onto HAP/γ-Fe2O3 nanocomposite could be well described by Freundlich and Sips models, while HA adsorption process on the adsorbent obeyed pseudo-second-order kinetics and the adsorption rates decreased with increasing initial HA concentration. This study showed that the HAP/γ-Fe2O3 nanocomposite could be used as an efficient and magnetically separable adsorbent for the removal of HA from aqueous solution. Subsequent studies demonstrated that the HA-loaded HAP/γ-Fe2O3 nanocomposite could be further applied for the highly efficient adsorption of methylene blue (MB) and separated from the medium by a simple magnetic process.

Interaction of humic acids with soil minerals: adsorption and surface aggregation induced by Ca2+

Environmental context Humic acids, important components of natural organic matter in soils, sediments and aquatic media, can interact with the surface of minerals affecting key environmental processes. In the presence of calcium, humic acids can also interact among themselves leading to molecular aggregates. We demonstrate that a solid mineral surface facilitates the formation of humic acid aggregates, and thus surface aggregation occurs under conditions where normal aggregation in solution does not occur. Abstract Humic acids (HAs) interact with the surface of mineral particles leading to the formation of clay–humic complexes that affect the transport of nutrients and contaminants in the environment, soil structure, soil erosion and carbon sequestration by soils. The interaction is influenced by the presence of multivalent ions, such as Ca2+, which enhances the uptake of HAs by the particles. This article reports the effects of Ca2+ on the interaction between a HA and a soil clay fraction, both obtained from the same soil sample. The study was performed by using zeta potential measurements, HA adsorption isotherms, Ca2+ adsorption isotherms and microscopy. The results show that at low HA concentrations and low Ca2+ concentrations HA adsorption takes place, but that at high concentrations surface aggregation and precipitation also takes place, a process that is seldom reported or analysed in the literature. HA adsorption isotherms only give the overall HA uptake by the solid but they do not allow differentiation of HA adsorption from surface aggregation. However, HA adsorption v. Ca2+ concentration plots and Ca2+ adsorption isotherms at different HA concentrations can distinguish these two processes quite clearly. In addition, surface aggregation could be undoubtedly observed with optical microscopy. Surface aggregation starts to take place at a 0.7mM Ca2+ concentration, which is lower than the Ca2+ concentration needed to start HA aggregation in solution. This indicates that the surface of soil minerals acts as a nucleation centre for HA aggregation.

Fate of atrazine in a soil under different agronomic management practices

Agricultural management affects the movement of atrazine in soil and leaching to groundwater. The objective of this study was to determine atrazine adsorption in a soil after 20 years of atrazine application under agronomic management practices differing in tillage practice (conventional and zero tillage), residue management (with and without residue retention) and crop rotation (wheat-maize rotation and maize monoculture). Atrazine sorption was determined using batch and column experiments. In the batch experiment, the highest distribution coefficient Kd (1.1 L kg−1) at 0–10 cm soil depth was observed under zero tillage, crop rotation and residue retention (conservation agriculture). The key factor in adsorption was soil organic matter content and type. This was confirmed in the column experiment, in which the highest Kd values were observed in treatments with residue retention, under either zero or conventional tillage (0.81 and 0.68 L kg−1, respectively). Under zero tillage, the fact that there was no soil movement helped to increase the Kd. The increased soil organic matter content with conservation agriculture may be more important than preferential flow due to higher pore connectivity in the same system. The soil's capacity to adsorb 2-hydroxyatrazine (HA), an important atrazine metabolite, was more important than its capacity to adsorb atrazine, and was similar under all four management practices (Kd ranged from 30 to 40 L kg−1). The HA adsorption was attributed to the type and amount of clay in the soil, which is unaffected by agronomic management. Soils under conservation agriculture had higher atrazine retention potential than soils under conventional tillage, the system that predominates in the study area.

Cu<sup>2+</sup> Removal by Hydroxyapatite Nanorods Prepared by Surfactant-Templated Method

Nanohydroxyapatite (HA) with rod-like shape was synthesized by a cationic surfactant-templated method. Batch adsorption experiments were conducted to investigate its copper adsorption property from aqueous solution. The effect of initial copper ion concentration and contact time were studied. Results showed that HA adsorption capacity increased from 25.6 mg/g to 81.4 mg/g with the increase of initial copper ion concentration from 20 mg/L to 200 mg/L. Meanwhile, the removal efficiency decreased from 64.1% to 20.3%. Moreover, it also revealed that the removal efficiency of Cu2+increased with the increasing contact time and the initial adsorption process is rapidly increased within 15 min and the equilibrium was attained after 15 min.

Distinct Effects of Humic Acid on Transport and Retention of TiO2 Rutile Nanoparticles in Saturated Sand Columns

The distinct effects of humic acid (HA, 0-10 mg L(-1)) on the transport of titanium dioxide (rutile) nanoparticles (nTiO(2)) through saturated sand columns were observed under conditions of environmental relevance (ionic strength 3-200 mM NaCl, pH 5.7 and 9.0). Specifically, the transport of nTiO(2) was dramatically enhanced in the presence of HA at pH 5.7, even at a low HA concentration of 1 mg L(-1). The mobility of nTiO(2) was further increased with greater concentrations of HA. In contrast, this enhancement of the nTiO(2) transportability due to the presence of HA was limited at pH 9.0 because of the negligible adsorption of HA onto nTiO(2), regardless of the concentrations of HA examined in this study. The distinct effects can be explained by the adsorption behaviors of HA to nTiO(2) and sand surfaces and the resulting interactions between nTiO(2) and sand surfaces under different conditions, which resulted in a large variation of the nTiO(2) transport and deposition behaviors at various conditions. In addition, theoretical interaction energy calculations and additional elution experiments indicate that the secondary energy minimum played an important role in controlling the nTiO(2) transport and deposition in porous media observed in this study. Moreover, the interaction energy calculations suggest that at pH 5.7, HA affected nTiO(2) transport by increasing the negative surface charge of nTiO(2) at low HA adsorption densities; whereas, combinations of increased electrostatic and steric interactions due to the presence of HA were the main mechanisms of enhanced transportability of nTiO(2) at high HA adsorption densities. Overall, results from this study suggest that natural organic matter and solution pH are likely key factors that govern the stability and mobility of nTiO(2) in the natural aquatic environment.

Design of Serum Compatible Tetrary Complexes for Gene Delivery

A novel gene delivery system, called PoSC, consisting of PEI, PSP, and HA is described. In contrast to the DNA/PEI/HA ternary system whose transfection efficiency decreases significantly with increasing serum concentration, PoSC exhibits a high transfection efficiency of about 51 and 87% for NIH3T3 and HCT116 cells, respectively, at 50% serum concentration. Furthermore, PoSC shows no cytotoxic effect at its working concentration. The overall results suggest that HA adsorption on cationic complexes enhances the transfection efficiency, while PSP is essential for high transfection efficiency at higher serum concentration.

Mutual Effects of Pb(II) and Humic Acid Adsorption on Multiwalled Carbon Nanotubes/Polyacrylamide Composites from Aqueous Solutions

This paper examines the adsorption of Pb(II) and a natural organic macromolecular compound (humic acid, HA) on polyacrylamide (PAAM) -grafted multiwalled carbon nanotubes (denoted as MWCNTs/PAAM), prepared by an N(2)-plasma-induced grafting technique. The mutual effects of HA/Pb(II) on Pb(II) and HA adsorption on MWCNTs/PAAM, as well as the effects of pH, ionic strength, HA/Pb(II) concentrations, and the addition sequences of HA/Pb(II) were investigated. The results indicated that Pb(II) and HA adsorption were strongly dependent on pH and ionic strength. The presence of HA led to a strong increase in Pb(II) adsorption at low pH and a decrease at high pH, whereas the presence of Pb(II) led to an increase in HA adsorption. The adsorbed HA contributed to modification of adsorbent surface properties and partial complexation of Pb(II) with the adsorbed HA. Different effects of HA/Pb(II) concentrations and addition sequences on Pb(II) and HA adsorption were observed, indicating different adsorption mechanisms. After adsorption of HA on MWCNTs/PAAM, the adsorption capacity for Pb(II) was enhanced at pH 5.0; the adsorption capacity for HA was also enhanced after Pb(II) adsorption on MWCNTs/PAAM. These results are important for estimating and optimizing the removal of metal ions and organic substances by use of MWCNT/PAAM composites.

Adsorption of humic acid to aminopropyl functionalized SBA-15

Humic acid is generally considered as one of ubiquitous pollutants in surface and ground water. In this study, aminopropyl functionalized SBA-15 adsorbents with varied aminopropyl contents were prepared via the co-condensation method and characterized by elemental analysis, X-ray diffraction, N 2 adsorption, IR spectroscopy and zeta-potential measurements. The adsorption behaviors of the adsorbents for humic acid were investigated using batch experiments and adsorption kinetic tests. SBA-15 exhibited low humic acid adsorption amount. In contrast, substantially enhanced humic acid adsorption was observed over aminopropyl functionalized SBA-15 adsorbents. Humic acid adsorption over the adsorbents could be well described using Langmuir adsorption model and the maximum humic acid adsorption capacities were found to be 8.5, 72.5 and 117.6 mg g −1 for SBA-15, APTS-SBA-15-5% and APTS-SBA-15-10%, respectively. In addition, increasing solution pH led to monotonically decreased humic acid adsorption over aminopropyl functionalized SBA-15. Humic acid adsorption process over functionalized SBA-15 could be well described using pseudo-second-order kinetic model and HA adsorption was controlled by both external and intraparticle diffusion based on the fitting results using Weber–Morris model.