Behavior and Mechanism of Tannic Acid Adsorption on the Calcite Surface: Isothermal, Kinetic, and Thermodynamic Studies

Preparation of nanocellulose light porous material adsorbed with tannic acid and its application in fresh-keeping pad

This study fabricated nanocellulose lightweight porous material (TOCNF-G-LPM-TA) as absorbent fresh-keeping pad for meat products, using TEMPO-oxidized cellulose nanofibril (TOCNF) and gelatin as structural skeleton and tannic acid (TA) as antibacterial component of TOCNF lightweight porous material (TOCNF-G-LPM). The adsorption kinetics, capacity and mechanism of TOCNF-G-LPM in different initial concentrations of TA solutions were investigated, the antioxidant and antibacterial properties of TOCNF-G-LPM-TA and its fresh-keeping effect on refrigerated pork at 4 ℃ were studied. Due to strong hydrogen bonding and porous structure, TOCNF-G-LPM exhibited excellent TA adsorption ability (230 mg/g) conforming with pseudo-second-order kinetic and Langmuir isotherm models. TA endowed TOCNF-G-LPM with good antioxidant and antibacterial activities. According to changes in appearance, pH and TVB-N values of pork during storage at 4 ℃, TOCNF-G-LPM-TA effectively extended the shelf life of refrigerated pork. This work provides a facile method for preparing nanocellulose based absorbent fresh-keeping pads.

Difficulties and Recent Achievements in Flotation Separation of Fluorite from Calcite—An Overview

As an important strategic non-metallic mineral resource, fluorite has been widely used in various industrial fields, such as metallurgy, optics and semiconductor manufacturing, as well as fluorine-related chemical engineering. Since the major gangue minerals of fluorite ore are silicate and carbonate ones, flotation is the main beneficiation method for the concentration. Compared with the relatively easy operation for silicate-type fluorite ore, fluorite concentration from calcite has always been the most difficult challenge in the field of mineral processing. In this review, analyses of the fundamental reasons for the difficulties of flotation separation of fluorite from calcite are performed, from the similar surface properties of both calcium minerals to the deterioration by the interference of dissolved ions in the pulp during grinding and flotation. Recent achievements in the flotation separation of fluorite from calcite as the main contents are comprehensively summarized, covering all aspects of flotation reagents of collectors, depressants and modifiers. Finally, successful examples of industrial practices forfluorite and calcite flotation separation are introduced. This overview provides a detailed and comprehensive reference source for the current research status of fluorite and calcite flotation separation, and some suggestions for future research are provided.

Synthesis of green magnetic biopolymer derived from Oak fruit hull tannin for efficient simultaneous adsorption of a mixture of Malachite Green and Sunset Yellow dyes from aqueous solutions

In the present study, a new bioadsorbent with polyhydroxyphenyl groups was synthesized as a tannin-based magnetic porous organic polymer by using from internal layer of Oak fruit hull (Oak Gal)...

Insights into the adsorption mechanism of tannic acid by a green synthesized nano-hydroxyapatite and its effect on aqueous Cu(II) removal

The polyphenolic tannic acid (TA) has been widely used in the stabilization and surface modification of nanomaterials. The interaction mechanism of TA with the biogenic nano-hydroxyapatite (nHAP) and its environmental importance, however, are poorly understood. This study explored the adsorption of TA using the green synthesized, eggshell-derived nHAP and implications of this process for the removal of aqueous Cu(II) via batch adsorption experiments, Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) investigations. TA adsorption by nHAP was a complex pH-dependent process and significantly correlated with TA molecule speciation and amphoteric properties of nHAP via multiple adsorption modes including surface complexation, electrostatic attraction, and hydrogen bond. The maximum TA adsorption amount was found to be 94.8 mg/g for less crystalline nHAP with lower calcination temperature. In the ternary Cu-TA-nHAP systems, TA promoted Cu(II) adsorption at pH < 5 and reduced Cu(II) uptake at pH > 5. Further studies of the effects of ionic strength and addition sequences, as well as Raman, FTIR, and XPS analyses revealed Cu(II) adsorption on nHAP was mainly dominated by inner-sphere surface complexation. These results can shed light on not only the utility of biogenic nHAP for TA and Cu(II) adsorption but also the evaluation of the effect of TA on the environmental behavior of heavy metals.

Preparation and pore-forming mechanism of hydrogen bond and ionic bond double-driven chitosan-based mesoporous carbon

Using chitosan as the carbon source, F127 as the template, and sodium tripolyphosphate as cross-linking agent, a hydrogen bond and ionic bond double-driven mesoporous carbon material was prepared via the sol-hydrothermal method and its formation mechanism was discussed. According to the results from FTIR, Raman, XPS, physical adsorption analyzer, SEM, TEM, and TG-IR, the mesoporous carbon material was formed under the synergistic effect of hydrogen bond and ionic bond has a mesoporous volume of 0.44 cm³/g, a BET surface area of 262 m²/g, and possesses the ideal unimodal distribution around 2.20 nm. The mesopores are originated from the degradation of hydrophobic segment PPO of F127, and the micropores come from the gases CO₂, CO, NH₃, CH₄, tetraethylene glycol dimethyl ether, and 2,6-diisopropylphenyl isocyanate produced during the degradation of prepolymers. The maximum adsorption capacity of this mesoporous carbon for tannic acid (Sips model) at 30 °C is 70.4 mg/g.

Treatment of Palm Oil Refinery Effluent Using Tannin as a Polymeric Coagulant: Isotherm, Kinetics, and Thermodynamics Analyses

The refining of the crude palm oil (CPO) generates the palm oil refinery effluent (PORE). The presence of high contents of biochemical oxygen demand (BOD), chemical oxygen demand (COD), turbidity, and suspended solids (SS) in PORE encourages the determination of an effective treatment process to minimize the environmental pollution and preserve aquatic life. In the present study, a biodegradable natural polymer, namely tannin, was utilized as a coagulant to treat PORE. The coagulation experiment was conducted using a jar test apparatus. The tannin coagulation efficiency was evaluated based on the BOD, COD, turbidity, and SS removal from PORE by varying the tannin dose (50-300 mg/L), pH (pH 4-10), treatment time (15-90 min), and sedimentation time (15-90 min). It was found that the maximum removal of BOD, COD, turbidity, and SS was 97.62%, 88.89%, 93.01%, and 90.21%, respectively, at pH 6, a tannin dose of 200 mg/L, 60 min of coagulation time, and 60 min of sedimentation time. Analyses of isotherm models revealed that the Freundlich isotherm model was well fitted with the coagulation study. Kinetics studies show that the pseudo-second-order kinetics model was the well-fitted kinetics model for the BOD, COD, turbidity, and SS removal from PORE using tannin as a polymeric coagulant. The determination of thermodynamics parameters analyses revealed that BOD, COD, turbidity, and SS removal from PORE was spontaneous, exothermic, and chemical in nature. The finding of the present study shows that tannin as a natural polymeric coagulant would be utilized in PORE treatment to avoid toxic sludge generation.

Synthesis of Cost-Effective Pomelo Peel Dimethoxydiphenylsilane-Derived Materials for Pyrene Adsorption: From Surface Properties to Adsorption Mechanisms

This study investigated the adsorption behaviors of pyrene (PYR) on a pomelo peel adsorbent (PPA), biochar (PPB), and H₃PO₄-modified (HPP), NaOH-activated (NPP), and dimethoxydiphenylsilane-treated (DPDMS-NPP) pomelo peel materials. SEM, FTIR, and elemental analyses of DPDMS-NPP's surface structure showed that the material was characterized by a well-developed porous structure, a large specific surface area (698.52 m² g^-1), and an abundance of phenyl functional groups. These properties enhance the PYR adsorption performance of DPDMS-NPP. Experimental results indicated that the adsorption capacity of DPDMS-NPP was significantly affected by the amount of material used and the initial concentration of PYR. Kinetic assessments suggested that PYR adsorption on PPA, NPP, and DPDMS-NPP could be accurately described by the pseudo second-order model. The adsorption process was controlled by several mechanisms, including electron donor-acceptor (EDA), electrostatic, and π-π interactions as well as film and intraparticle diffusion. The adsorption isotherm studies showed that PYR adsorption on DPDMS-NPP and PPA was well described by the Langmuir model and the maximum Langmuir adsorption capacity of DPDMS-NPP was 531.9 μg g^-1. Overall, the results presented herein suggested that the use of DPDMS-NPP adsorbents constitutes an economic and environmentally friendly approach for the mitigation of PYR contamination risks.