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... kinetics of phosphate adsorption by P(AAC-co-DMAPAA) is shown in Fig. 8. It was obviously found that the adsorption process of phosphate onto P(AAC-co-DMAPAA) was very fast at the initial stage and thereafter the amount of phosphate adsorbed onto the hydrogels increased slowly with increasing contact time until the adsorption equilibrium was reached. The corresponding time to reach the 96.4% of phosphate ...
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... capacity was within 5 h. Such a rapid adsorption rate may be a consequence of the electrostatic attraction force between phosphate and P(AAC-co-DMAPAA) with more positively charged surface at pH 2.0 [37]. In order to examine the adsorption process, the pseudo-first-order and pseudo-second-order models in Table 2 were used to fit the curves in Fig. 8. The pseudo-first-order model assumes that physisorption limits the adsorption rate of the particles onto the adsorbent, while the pseudo-second-order model considers chemisorption as the rate-limiting mechanism of the process [38]. The obtained kinetic parameters in Table 2 show that the kinetic data was better fitted with ...
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Strong adhesion between hydrogels and various engineering surfaces has been achieved; yet, achieving fatigue-resistant hydrogel adhesion remains challenging. Here, we examine the fatigue of a specific type of hydrogel adhesion enabled by hydrogen bonds and wrinkling and show that the physical interactions–based hydrogel adhesion can resist fatigue...
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... It is generally assumed that adsorption is a physical process in the pseudo-first-order model controlled by mass transfer from the adsorbate to the surface. In comparison, the pseudo-second-order model explains chemisorption as the dominant adsorption process 71 . Figure 17 shows the plots of pseudo-first-order and pseudo-second-order adsorption kinetic models. ...
Arsenite (As(III)) is the most toxic form of arsenic that is a serious concern for water contamination worldwide. Herein a ZnO/Halloysite (Hal) nanocomposite was prepared by the chemical bath deposition method (CBD) through seed-mediated ZnO growth on the halloysite for eliminating As(III) from the aqueous solution. The growth of ZnO on seeded halloysite was investigated based on the HMTA: Zn2+ molar ratio in the solution. An optimum molar ratio of HMTA:Zn for nucleation and growth of ZnO upon halloysite was obtained 1:2 based on morphological analysis. The TGA results confirmed that thermal stability of HNT was enhanced by ZnO decoration. The prepared ZnO/Hal nanocomposite at optimal conditions was employed for arsenite (As(III)) removal from aqueous solutions. Experimental data were evaluated with different isothermal, thermodynamic, and kinetic models. Based on the zeta potential results, Hal nanocomposites had a greater negative value than pure Hal. Therefore, the ZnO/Hal nanocomposite exhibited efficient As(III) adsorption with a removal efficiency of 76% compared to pure Hal with a removal efficiency of 5%. Adsorption isotherm was well correlated by both non-linear Langmuir and Sips models, exhibiting maximum adsorption capacity of As(III) at 42.07 mg/g, and 42.5 mg/g, respectively. As a result of the study, it was found that the fabricated Hal nanocomposite with low toxicity can be used effectively in water treatment.
... This indicates that the adsorption rate depends on the adsorption capacity and not on the concentration of adsorbates as defined by the chemical sorption, or chemisorption phenomenon. [54,55] ...
The removal of heavy toxic metals from industrial effluents is extremely important, especially for mercury (Hg), which is classified as a highly toxic even at low concentrations. For this purpose, novel thiourea chelating resins were synthesized as sorbent for Hg (II). Six different polymers of formo‐phenolic types were characterized and evaluated for their chelating properties with respect to Hg (II) extraction. Batch adsorption studies of mercury (II) as a function of pH, initial metal ion concentration, temperature, and time showed that thiourea formo‐phenolic polymers have a good affinity for Hg removal and a high adsorption capacity. Adsorption isotherms (Langmuir and Freundlich) and kinetic models (pseudo‐first and pseudo‐second order) were used to interpret the sorption behavior of the materials. The Langmuir model yielded the best fit with a maximum adsorption capacity of 300 mg/g. Desorption studies were performed with aqueous thiourea solution and showed that the adsorbent is indeed regenerable and can be effectively used for up to three adsorption‐desorption cycles with negligible loss of performance. This study confirmed the potential of thiol‐modified formo‐phenolic resins in sorbent engineering with promising applications in the remediation of mercury‐contaminated water.
... The PFO model is based on a direct proportion between the rate of adsorption and the difference in equilibrium concentration and the amount adsorbed with time 52 . Also, the PFO is common for adsorption systems in which adsorption occur via diffusion thru the interface and physisorption is the rate determining step [53][54][55] . ...
A commercial carbon cloth (CC) was oxidized by HNO3 acid and the features of the plain and oxidized CC were evaluated. The results of characterization illustrated that HNO3 oxidization duplicated the oxygen-containing functional groups and the surface area of the CC. The adsorption performance of the plain and oxidized CC (Oxi-CC) toward benzotriazole (BTR) was compared. The results disclosed that the uptake of BTR by oxidized CC was greater than the plain CC. Thence, the affinity of oxidized CC toward BTR was assessed at different conditions. It was found that the adsorption was quick, occurred at pH 9 and improved by adding NaCl or CaCl2 to the BTR solution. The kinetic and isotherm studies revealed that the surface of Oxi-CC is heterogeneous and the adsorption of BTR follows a physical process and forms multilayer over the Oxi-CC surface. The regenerability and reusability study illustrated that only deionized water can completely regenerate the Oxi-CC and that the Oxi-CC can be reused for five cycles without any loss of performance. The high maximum adsorption capacity of Dubinin-Radushkevich isotherm model (252 mg/g), ease of separation and regeneration, and maintaining the adsorption capacity for several cycles revealed the high efficiency and economical and environmental feasibility of Oxi-CC as an adsorbent for BTR.
... On the report of the higher value of R 2 and lower error functions (Table 4), it has been established that the linear variant of the pseudo-second-order model exhibits optimal suitability for the analysis of the adsorption process. The outcome of the pseudo-secondorder mechanism analysis indicates that the interactions between the IC dye and the GG hydrogel/MnFe LDH/GO/Fe 3 O 4 nanocomposite were chemical type in nature [41]. ...
The primary objective of this investigation was to synthesize a novel antibacterial nanocomposite consisting of natural gellan gum (GG) hydrogel, MnFe LDH, GO, and Fe3O4 nanoparticle, which was developed to adsorb Indigo carmine (IC). The GG hydrogel/MnFe LDH/GO/Fe3O4 nanocomposite was characterized through different analytical, microscopic, and biological methods. The results of adsorption experiments reveal that 0.004 g of the nanocomposite can remove 98.38 % of IC from a solution with an initial concentration of 100 mg/L, within 1 h at room temperature and under acidic pH conditions. Moreover, the nanocomposite material effectively suppressed the in vitro growth of both E. coli and S. aureus strains, with inhibitory rates of 62.33 % and 53.82 %, respectively. The isotherm data obtained in this investigation were fitted by linear and non-linear forms of Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms equations. The results of the adsorption kinetics study indicated that the pseudo-second-order model best described the experimental data. The findings of this study suggest that the synthesized nanocomposites hold great potential as effective adsorbents for removing IC and bacteria from aqueous solutions.
... The value of pH pzc is the point where the curve of ΔpH (=pH f − pH i ) versus pH i crosses the line equal to zero by the pH drift method. 12,56,57 ■ ASSOCIATED CONTENT ...
This work dealt with a potential and effective method to reuse modified alginate beads after the removal of Cu(II) ions for efficient adsorption of tetracycline (TC) from aqueous solutions. The modified alginate beads were fabricated by a polyacrylamide (PAM) network interpenetrated in alginate−Ca 2+ network (PAM/CA) decorated with polyethylene glycol as a pore-forming agent. The porous PAM/CA was characterized using scanning electron microscopy, Brunauer−Emmett− Teller, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy analysis. The adsorption kinetics, isotherms, adsorption stability, and reusability studies of the adsorbent toward Cu(II) ions were scrutinized. The column performance of porous PAM/CA was tested with Cu(II)-containing electroplating wastewater. After Cu(II) adsorption, the Cu(II)-adsorbed PAM/CA (PAM/CA@Cu) was applied to remove TC from aqueous solutions without any regeneration process. The effects of pH, initial TC concentration, ionic strength, and coexisting ions on the adsorption were also discussed in detail. Compared with many reported adsorbents, the PAM/CA@Cu exhibited an excellent adsorption performance toward TC with a maximum adsorption capacity of 356.57 mg/g predicted by the Langmuir model at pH 5.0 and 30°C with the absence of coexisting ions. The possible adsorption mechanism of TC onto the PAM/CA@Cu was revealed.
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Although water is essential for global health and the socio-economic development of modern society, providing fresh water universally in a sustainable and affordable manner, for both developing and industrialized communities, is challenging. Polymeric hydrogels have recently drawn increasing interest as promising material platforms to sustainably enhance global water security. This review aims to provide a consolidated overview of polymeric hydrogels as an enabling agent in various water treatment technologies. First, a summary of the different approaches for the preparation of hydrogels with tailored chemistry, morphology, structure, and functions that enable the multifaceted requirements of different water technologies to be met is presented. Then, a set of properties unique to hydrogels, which gives them competitive advantages compared to other materials in the context of water treatment, is presented and discussed. This is followed by a comprehensive review of the applications of hydrogels in different water technologies. Their performance is correlated to their unique properties in order to gain an in-depth mechanistic understanding of how hydrogels can lead to impressive performance and technological innovation. The authors conclude with some proposed solutions and recommendations for prospective research directions to address the remaining challenges specific to each hydrogel-enabled water technology.
The aim of this work is to examine the adsorption performance and mechanism of phosphorus (P) onto polyethyene polyamine (PEPA) grafted chitosan-zirconium(IV) composite beads (CS-Zr-PEPA) from aqueous solutions. The morphology, functional groups, and surface area of the CS-Zr-PEPA beads were characterized by SEM, FTIR, and BET analysis. Batch adsorption experiments were conducted via different operating parameters such as solution pH, initial phosphate concentration, co-existing anions and temperature. The adsorption kinetics, equilibrium isotherms and adsorption stability of the adsorbent were scrutinized. In comparison with other CS-based beads, the CS-Zr-PEPA had a greater affinity towards P and exhibited a maximum adsorption capacity of 103.96 mg-P/g predicted by Langmuir mode. The reusability studies of CS-Zr-PEPA beads were carried out. The CS-Zr-PEPA beads exhibit preferable sequestration of P through specific interactions, as further demonstrated by studying physicochemical characteristics of the virgin beads and P-adsorbed beads using X-ray photoelectron spectroscopy (XPS). The column performance of CS-Zr-PEPA beads was tested with P-containing wastewater. Results indicated that the developed CS-Zr-PEPA composite beads could be utilized as a promising adsorbent for effective removal and recovery of P from water and wastewater.
