Studying the Adsorptive Behavior of Poly(Acrylonitrile-co-Styrene) and Carbon Nanotubes (Nanocomposites) Impregnated with Adsorbent Materials towards Methyl Orange Dye

In this study, a polymeric (acrylonitrile-co-styrene) P(AN-co-St) composite was impregnated with adsorbents, such as sulfonated and multiwall carbon nanotubes (MWCNTs), to increase the adsorptive characteristics of the nanocomposite upon the removal of methyl orange (MO) dye under different conditions. A novel nanocomposite copolymer mixture of P(AN-co-St) and SP(AN-co-St) was used. MWCNTs were prepared by a low-cost chemical vapor deposition (CVD) process. Variation in MO adsorption onto the three nanocomposites was examined in an aqueous solution via the batch technique with respect to contact time, initial MO concentration, adsorbent dosage, pH, and temperature. The surface of the nanocomposites was characterized by a scanning electron microscope (SEM), particle size distribution (PSD), Fourier transform infrared (FTIR), and Raman analysis. The experimental data showed that the efficiency of P(AN-co-St)/ MWCNT removal increased under the conditions of an acidic pH (3 and 5) with an agitation speed of 140 rpm, a sorbent weight of 0.01 g, and 20 mg of initial dye. The maximum sorption capacities were 121.95, 48.78, and 47.84 mg g−1 for the P(AN-co-St)/ MWCNTs, SP(AN-co-St), and P(AN-co-St) composites, respectively, as assessed by the Langmuir model. Additional isotherm models, such as the Freundlich, Temkin, and Halsey models, were used to examine the experimental data. A pseudo-second-order model was found to be more fitting for describing the sorption.

Adsorptive Behavior of Prepared Metal-Organic Framework Composites on Phosphates in Aqueous Solutions

As an efficient water treatment method for treating dilute solution systems, electrosorption is promising for the separation and recovery of organic compounds, wastewater treatment, and deep purification of water. Here, two types of UiO-66 samples were prepared using the solvothermal synthesis method, and the effects of different regulators on the microstructure of materials were compared using the various characterization methods. The electrochemical properties of the activated carbon and two types of materials were tested by cyclic voltammetry and AC impedance spectroscopy, and the desalination effect of the materials on phosphate was investigated. The UiO-66 material with uniform-size particles, smaller-size particles, and more surface adsorption sites exhibited better phosphate removal and adsorption capacity. It was found that the desalination process of the UiO-66 material is reversible, and the adsorbent material can be reused, which is advantageous for engineering applications.

Preparation and characterization of activated carbon from wheat straw to remove2, 4-dichlorophenoxy acetic acid from aqueous solutions

This study was focused to investigate the adsorptive behavior of activated carbon prepared from wheat straw treated with acid and base for the removal of 2, 4-dichlorophenoxy acetic acid (2,4-D). The morphology of the adsorbent was characterized using infrared spectroscopy and scanning electron microscopy. Compared with acid activated wheat straw, base activated wheat straw has provided lower ash content, moisture and volatile matter. However, it has higher iodine number than acid activated wheat straw. The removal of 2,4-D from aqueous solution was investigated at various physicochemical parameters such as pH (2–10), contact time (5–60 min), temperature (20-80 oC), amount of adsorbent (0.1-1.4 g) and initial concentration of 2,4-D (1.0-25 mg/L). The removal efficiency of 2,4-D in aqueous solution was found to be 92.02%. The equilibrium data were analyzed using Langmuir and Freundlich isotherm and the Langmuir model better describes that the active adsorption sites were homogeneously distributed on the surface of the adsorbent. Therefore, the activated carbon prepared from wheat straw treated with base can be used as efficient and cost-effective method to remove 2,4-D from aqueous solution.

Tartaric Acid-Modified Holarrhena antidysenterica and Citrullus colocynthis Biowaste for Efficient Eradication of Crystal Violet Dye from Water

Two novel adsorbents Holarrhena antidysenterica (HA) and Citrullus colocynthis (CC) were collected from native Pakistan and treated with tartaric acid. The adsorbents were characterized by Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy, and their adsorptive behavior was studied against model cationic dye crystal violet (CV). Role of biosorbent dose, time of contact, temperature studies, agitation rates, and solution pH was investigated. Optimum conditions obtained for the removal of CV dye for H. antidysenterica-tartaric acid modified (HA-TA) were as follows: 0.8 g adsorbent dose, 35 minutes contact time, 5.0 pH, 40°C temperature, and 150 rpm agitation rates as compared to H. antidysenterica that gave 1.4 g adsorbent dose, 40 minutes time of contact, 6.0 pH, 50°C temperature, and 150 rpm agitation speed. C. colocynthis-tartaric acid modified (CC-TA) removed CV dye at 0.6 g adsorbent dose, 30 minutes contact interval, 4.0 pH, 40°C temperature, and 125 rpm agitation speed in contrast to C. colocynthis which gave 0.8 g adsorbent dose, 40 minutes time of contact, 6.0 pH, 50°C temperature, and 125 rpm agitation speed, respectively. Isothermal studies for both raw and modified biosorbents were compliant with the Langmuir model indicating monolayer, chemisorption. The maximum Langmuir capacities were up to 128.20 mg/g, 136.98 mg/g, 144.92 mg/g, and 166.66 mg/g for HA, CC, HA-TA, and CC-TA. Pseudo-second-order kinetic model well fitted the dye removal data. The rate-determining steps involved both surface and intraparticle diffusion mechanisms. Adsorption of dye molecules on active surfaces was governed by electrostatic attractions and chelating abilities. Thermodynamics research revealed the spontaneous and exothermic nature of the reaction. The adsorbents serve promising candidates for the effective removal of hazardous dyes from aqueous solutions.