Adsorption of dyes by ACs prepared from waste tyre reinforcing fibre. Effect of texture, surface chemistry and pH

Removal of Congo red dyes from aqueous solutions by porous γ-alumina nanoshells

Porous alumina has been shown to be an excellent adsorbent for Congo Red (CR) dye. In this work, highly porous g-Al₂O₃ nanoshells were synthesized from alumina coated carbon black (CB) obtained from a new deposition technique and used for removal of CR dye from aqueous solutions. Adsorption experiments were conducted in a batch mode and a series of parameters were investigated, including contact time, initial dye concentrations, ionic strength and pH of the solutions. It was found that equilibrium for CR adsorption can be reached within 30 min, much faster than reported by other studies in the literature on similar adsorbents. It was also found that the adsorption capacity of Al₂O₃ nanoshells is 44.8 % higher than that of alumina/CB. The adsorption capacity of Al₂O₃ nanoshells was more favorable at lower pH, and the optimal adsorption ability was achieved at pH 4.0 with a removal efficiency at 98.6 %. The Al₂O₃ nanoshells have a maximum adsorption capacity of 370.4 mg g^-1 (25 °C; pH 7; no salt added), better than or comparable to those reported in the literature. A pseudo-second-order kinetics model can best fit the kinetics of CR adsorption, which follows the Langmuir isotherm. The high adsorption capacity is attributed to the strong hydrogen-bonding interactions between the anionic dye and Al₂O₃ nanoshells surface as well as to the electrostatic interactions between CR dye and the Al₂O₃ nanoshells.

NiFe2O4@ nitrogen-doped carbon hollow spheres with highly efficient and recyclable adsorption of tetracycline

Antibiotics can affect ecosystems and threaten human health; therefore, methods for removing antibiotics have become a popular subject in environmental management and for the protection of human health. Adsorption is considered an effective approach for the removal of antibiotics from water. In this study, NiFe₂O₄@nitrogen-doped carbon hollow spheres (NiFe₂O₄/NCHS) were synthesized via a facile hydrothermal method followed by calcination using NCHS as a hard template. The nanocomposite exhibited high adsorption activity and good recyclability. The nanocomposite was characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, and nitrogen adsorption–desorption to study its micromorphology, structure, and chemical composition/states. In addition, the factors affecting the adsorption process were systematically investigated, including tetracycline (TC) concentration, solution pH, ionic strength, and temperature. The maximum adsorption capacity for TC was calculated to be 271.739 mg g⁻¹ based on the Langmuir adsorption model, which was higher than various other materials. This study provides an effective method for constructing the NiFe₂O₄/NHCS core–shell structure, which can be applied for the removal of TC from water.

Antibiotics can affect ecosystems and threaten human health; therefore, methods for removing antibiotics have become a popular subject in environmental management and for the protection of human health.

Optimized preparation of Phragmites australis activated carbon using the Box-Behnken method and desirability function to remove hydroquinone

In this study, preparation of Phragmites australis activated carbon (PAAC) was optimized and applied for the removal of hydroquinone from aqueous solution. The Box-Behnken surface design (3³) was used to statistically visualize the interactions among microwave power (A), microwave radiation time (B) and the ingredient ratio (C) (H₃PO₄: P. australis powder, in g). The desirability function was utilized to simultaneously optimize the multi-response indicators. A regression analysis showed that the experimental data of BBD optimization experimental results fit well to a quadratic model. PAAC was characterized according to its morphology, structure and composition. Dynamic adsorption data showed that the best fit was obtained by a pseudo-second-order model and the Freundlich isotherm model. The maximum adsorption capacity for hydroquinone adsorption onto PAAC was 156.25 mg/g at 30 ℃ and the adsorption mechanism may be attributed to multi-layer surface and chemisorption via donor-acceptor and coupling interaction of the electron. The present study showed that PAAC has the potential for use as a biosorbent for the adsorption treatment of water pollutants.

Rubber industry

Following chapter presents short introductory description of rubber and rubber industry. The main problem of rubber industry is the way of the usage of spent tires. Furthermore very important group of problems arise considering the metal and nonmetal additives which are significant component of the vulcanized rubber. The key attention is dedicated to typical ways of rubber usage in utilization and recovery of metals from spent rubber materials concentrating specifically on used tires processing. The method of recovery of rare metals from rubber tires was described. The rubber debris finds widest use in the field of waste metal solutions processing. The environmental pollution caused by metals poses serious threat to humans. Several applications of the use of waste rubber debris to remove metals from environmental waters were described. Moreover, the agriculture usage of waste tire rubber debris is described, presenting systems where the rubber material can be useful as a soil replacement.

New Composites LnBDC@AC and CB[6]@AC: From Design toward Selective Adsorption of Methylene Blue or Methyl Orange

New porous composites LnBDC@AC (AC = Activated carbon, Ln = Eu and Gd and BDC = 1,4-benzenedicaboxylate) and CB[6]@AC (CB[6] = Cucurbit[6]uril) were obtained using hydrothermal route. The LnBDC and CB[B] are located inside the pore of the carbon materials as was observed in SEM-EDS, XRPD and FT-IR analysis. Porosimetry analysis showed values typically between AC and LnBDC material, with pore size and surface area, respectively, 29,56 Å and 353.98 m²g^-1 for LnBDC@AC and 35,53 Å and 353.98 m²g^-1 for CB[6]@AC. Both materials showed good absorptive capacity of metil orange (MO) and methylene blue (MB) with selectivity as a function of pH. For acid pH, both materials present selectivity by MB and alkaline pH for MO, with notable performance for CB[6]@AC. Additionally, europium luminescence was used as structural probe to investigate the coordination environment of Eu³⁺ ions in the EuBDC@AC composite after adsorption experiment.