Tetracycline Adsorption from Aqueous Media by Magnetically Separable Fe3O4@Methylcellulose/APTMS (Isotherm, Kinetic and Thermodynamic Studies)

This study aimed to synthesize Fe3O4@Methylcellulose/3-Aminopropyltrimethoxysilane (Fe3O4@MC/APTMS) as a new magnetic nano-biocomposite by a facile, fast, and new microwave-assisted method and to be utilized as an adsorbent for tetracycline (TC) removal from aqueous solutions. Fe3O4@MC/APTMS was characterized by Fourier transform-infrared (FTIR), Field emission scanning electron microscopy (FESEM), Energy dispersive spectroscopy (EDS), Mapping, X-ray diffraction (XRD), Thermal gravimetric analysis (TGA), Brunauer–Emmett–Teller (BET) and vibrating sample magnetometer (VSM). The point of zero charge (pHzpc) value of the nano-biocomposite was estimated to be 6.8 by the solid addition method. Optimum conditions were obtained in TC concentration: 10 mg L−1, adsorbent dosage: 80 mg L−1, contact time: 90 min, and solution pH: 6 with the maximum TC removal of 90% and 65.41% in synthetic and actual samples, respectively. The kinetic and isotherm equations pointed to a pseudo-second order kinetic and Langmuir isotherm optimum fitting models. Based on the values of entropy changes (ΔS) (50.04 J/mol k), the enthalpy changes (ΔH) (9.26 kJ/mol), and the negative Gibbs free energy changes (ΔG), the adsorption process was endothermic, random, and spontaneous. The synthesized adsorbent exhibited outstanding properties, including proper removal efficiency of TC, excellent reusability, and simple separation from aqueous media by a magnet. Consequently, it is highly desirable that Fe3O4@MC/APTMS magnetic nano-biocomposite could be used as a promising adsorbent for TC adsorption from aqueous solutions.

Kinetic Study of Adsorption Active Carbon Cassava Skin for Removal of Acetic Acid from Aqueous Solution

The amount of liquid wastes containing acetic acid found from food industry such as tofu home industry released is relatively high and pollutes water quality and also environment nearby. Several methods reducing pollutant in liquid wastes are available, one of which is adsorption using carbon as an adsorbent. The production of cassava in Indonesia was about 23.936 tons in year 2013 which produced cassava’s skin wastes about 2.393 tons. Mostly these cassava’s skin wastes containing around 59.31% carbon is disposed as garbage. This research is to develop more on reducing acetic acid containing in liquid waste by carbon active from cassava’s skin with variation of particle sizes, reaction times and acetic acid liquid waste concentrations, and also to study the kinetic reaction of cassava skin active carbon adsorbing acetic acid between Freundlich and Langmuir isotherm equations. The result shows the kinetic adsorption follows Freundlich isotherm equation with maximum capacity of Cassava skin active carbon 0.7 mg/g at particle size of adsorbent of 0.3375 mm and reaction time of 105 minutes.

Sherry wine industry by-product as potential biosorbent for the removal of Cr(VI) from aqueous medium

A low-cost biosorbent obtained from the Palomino Fino grape seed, a Sherry wine industry by-product, has been proposed as a way of valorising this material. The biomass was characterised obtaining values of 0.68 ± 0.05 g mL−1 for bulk density, 1.02 ± 0.09 g mL−1 for apparent density and 33.3% for porosity. The pHpzc was 5.2 and the surface negative charge value was 2.4 ± 0.2 mmol g−1. The analysis of surface morphology showed differences due to the sorption. The results showed a promising potential for chromium(VI) removal from aqueous solutions. The studies were carried out in batch scale and a 23 factorial design was applied for the optimisation of the process. A percentage of 91.7 ± 0.6% was achieved for the biosorption of Cr(VI) under optimal conditions using pH 5.5, 15 g/L of biosorbent and 8 h of contact time. The biosorption capacity showed a remarkable linearity from 0 to 2 mmol L−1 Cr(VI) and a precision of 0.64% for the removal of 1 mmol L−1 of metal. Langmuir, Freundlich and Temkin isotherm equations and the parameters of six kinetic models were used in the equilibrium modelling and identifying the mechanism of the biosorption. The combination of physical and chemical sorption mechanisms was proposed for the chromium removal with a high maximum sorption capacity (qmax = 208.3 mg g−1). Thermodynamic parameters indicated the spontaneous and endothermic nature of the chromium removal. The successful biosorption was based on the special grape seed components with a relevant content in antioxidant and lignocellulosic compounds.

Langmuir and Freundlich isotherm equation test on the adsorption process of Cu (II) metal ions by cassava peel waste (Manihot esculenta crantz)

This Study aims to determine the adsorption process of Cu (II) metal by cassava peel waste (Manihot esculenta crantz) meeting the Langmuir equation and Freundlich. Research method cassava peel made into activated carbon, then determine the mass, pH and optimum contact time. Then the determination of the maximum adsorption capacity was carried out by testing with the Langmuir isotherm and Freundlich isotherm equations. The results showed that the best conditions (optimal conditions) were obtained with the addition of 0.5 grams of active carbs from cassava peels. The percentage of Cu ion adsorption in these conditions was 97.72%, at pH 6 and a contact time of 60 minutes and the absorption capacity was 98.49%. The maximum adsorption capacity of cassava peel activated carbon to Cu(II) ions at the optimum condition was determined based on the Langmuir and Freundlich isotherm equations. The results obtained were-51.813 mg/g and 26,792 mg/g, respectively.

Preparation and Characterization of Cattail-Derived Biochar and Its Application for Cadmium Removal

Biochars produced from aquatic plants have attracted increasing attention for the removal of heavy metals from the environment. Therefore, biochars derived from the roots (CBR), stems (CBS) and leaves (CBL) of cattail were investigated in this paper for their higher adsorption capacity, particularly for Cd(II). The adsorption characteristics and the leaching of alkali (soil) metals within biochars obtained from the different tissues of cattail were also discussed. The results showed that the specific surface area of cattail root biochar reached 15.758 m2 g−1. Langmuir, Freundlich and D-R isotherm equations were used to fit the experimental data, and the last equation revealed the best fitting result. The adsorption kinetics for Cd(II) removal were determined by using two different models. The experimental data for CBR and CBS were in good agreement with the pseudo second-order model, whereas the pseudo first-order model provided a better fit for CBL. The amount of leached K reached 73.214 mg g−1 in CBS (55.087 mg g−1 in CBL), which was almost an order of magnitude higher than those of Mg and Ca. The experimental data showed that the leached Mg and Ca metals in CBL had maximum levels of 6.543 and 10.339 mg g−1, respectively. The mechanism of Cd(II) sorption by the biochar is complex and probably involves a combination of mass transfer, ion exchange, and mineral precipitation through the macropores and micropores of the biochar in the sorption process.

Water Purification by Potassium Humate–C.I. Basic Blue 3 Adsorption-Based Interactions

Interactions of C.I. Basic Blue 3 with potassium humate in aqueous systems were investigated. Both the humic content and dye removal are of crucial significance in relation to water of a desired quality. Dye retention experiments demonstrated that potassium humate is an exceptionally efficient adsorbent. The effect of both the pH and temperature on the adsorption process was investigated. The temperature proved to only slightly influence the extent of dye sorption; contrarily, under mildly acidic conditions (pH = 4.0), the quantity of dye adsorbed was doubled on standing. At this pH value, interactions between the positively charged dye and the dissociated carboxyl groups of humic substances are encountered. This was also supported by the obedience of the experimental data to the pseudo-second-order kinetic model. Three adsorption models, i.e., Langmuir, Freundlich and BET, were fitted to the experimental data; the equilibrium adsorption conformed to the Langmuir and BET isotherm equations on the basis of electrostatic dye–humics interactions, while the fitting of the Freundlich model referred to the heterogeneities of humic substances attributed to their colloidal behavior. Thermodynamic quantities, i.e., enthalpy, entropy and free energy change in the adsorption, were calculated. The low ΔHadsθ values verify the negligible effect of the temperature on the adsorption; ΔSadsθ denotes a thermodynamically favorable reaction, and ΔGadsθ denotes a spontaneous process.

Reduction of Cd(II) Ions in the Presence of Tetraethylammonium Cations. Adsorption Effect on the Electrode Process

The effect of the adsorption of tetraethylammonium (TEA) cations, which present both ionic and organic characteristics, on the reduction of Cd(II) ions have been studied from dc and ac measurements at the dropping mercury electrode. The resistance to the charge transfer (Rct) and Warburg coefficient (σ) parameters have been determined through impedance measurements. Thus, the global velocity constant has been obtained. The reduction process of Cd(II) in perchloric media is reversible and is affected by the adsorption of TEA cations, especially at high TEA concentrations. Values of E1/2, half wave potential, and DO, diffusion coefficient, obtained from both dc and ac measurements agree. The velocity constants show a decrease as TEA concentration increases, with values ranging from 0.6 to 0.01 cm·s−1. The inhibitory effect of TEA adsorption on the electrode process and the relationship between electrode coverage, θ, and velocity constants, K, using several isotherm equations, have been discussed. The best fit was obtained with the equation K = 0K(1 − θ)a with an a value close to three, indicating a blocking effect and electrostatic repulsion due to TEA.

Sorption of Pharmaceuticals in Aqueous Solution Using Insoluble β-Cyclodextrin Polymers

The present study was aimed at evaluating the ability of insoluble β-cyclodextrin polymers (βCDps) to recover pharmaceuticals from aqueous solutions. Two different β-cyclodextrin polymers, one composed of epichlorohydrin-cross linked β-cyclodextrin and the other a β-cyclodextrin-polyurethane, were prepared by condensation polymerization and addition polymerization of βCD using epichlorohydrin (EP) and diisocyanatohexane (HDI) as cross linking agents, respectively. The contaminants tested were naphthalene, naproxen, nabumetone, 2-naphthol, pyrene and propranolol which represent model pharmaceutical molecules. The adsorption isotherms of the organics and βCDPs were well described by Freundlich isotherm equations. The trapping efficiencies were determined using fluorescence spectroscopy as the analytical technique. Based on the results of this study, it was found that the epichlorohydrin-cross linked β-cyclodextrin polymers were more efficient in adsorption of organic contaminants both in batch and column systems when compared with β-cyclodextrin-polyurethane polymers. Reasons for these differences are discussed.

Sorption of Pharmaceuticals in Aqueous Solution Using Insoluble β-Cyclodextrin Polymers

The present study was aimed at evaluating the ability of insoluble β-cyclodextrin polymers (βCDps) to recover pharmaceuticals from aqueous solutions. Two different β-cyclodextrin polymers, one composed of epichlorohydrin-cross linked β-cyclodextrin and the other a β-cyclodextrin-polyurethane, were prepared by condensation polymerization and addition polymerization of βCD using epichlorohydrin (EP) and diisocyanatohexane (HDI) as cross linking agents, respectively. The contaminants tested were naphthalene, naproxen, nabumetone, 2-naphthol, pyrene and propranolol which represent model pharmaceutical molecules. The adsorption isotherms of the organics and βCDPs were well described by Freundlich isotherm equations. The trapping efficiencies were determined using fluorescence spectroscopy as the analytical technique. Based on the results of this study, it was found that the epichlorohydrin-cross linked β-cyclodextrin polymers were more efficient in adsorption of organic contaminants both in batch and column systems when compared with β-cyclodextrin-polyurethane polymers. Reasons for these differences are discussed.

Application of dimensional analysis in removal prediction of 2-[4-(dimethylamino) styryl]-1-methylpyridinium iodide dye using humic acid coated magnetic nanoparticle

<p>Numerous factors affect adsorption phenomena in solid–liquid systems. Critical factors are the sorbent dose and initial concentrations of the contaminants in the system. However, the combination of these two factors and their effects on removal prediction are largely unexplored. In this study, batch experiments were conducted to examine such effects on the adsorption of 2-[4-(dimethylamino) styryl]-1-methylpyridinium iodide cationic dye (2-ASP) in contaminated water to humic acid coated magnetic nanoparticles (HA-MNPs). Dimensional analysis and Buckingham’s π theorem were subsequently used to assess the relationship between the sorbent dose, initial concentration, and percent removal. Results of dimensional analysis along with experimental data suggest that sorbent dose and sorbate concentration ratio are the main variables controlling sorption of dye on HA-MNPs. In conventional isothermal studies, the isotherm equations are developed based on experiments of one sorbent dose which cannot be generalized for all sorbent doses.  In this study, a power function (Isotherm-like) model was obtained from the dimensional analysis that can describe precisely the sorption process of dye on HA-MNPs as a function of equilibrium concentration and sorbent dose ratio. Moreover, a relation is deduced for prediction of removal percent as a function of sorbent dose and initial concentration ratio with R<sup>2</sup> of 0.98.</p><p><strong>Keywords: Remediation, Dimensional analysis, Isotherm-like model, Magnetic nanoparticle, Styryl pyridinium dyes, Water treatment</strong></p>