Volume 235, Issue 3

Here in, we report the synthesis and characterization of ZnO–TiO 2 composite as a potential photo catalyst for photo degradation of methyl orange under UV irradiation. ZnO–TiO 2 with 1:1 ratio was synthesized via wet incipient impregnation method using TiO 2 and Zn(NO 3 ) 2 ⋅ 6H 2 O as precursor material and the prepared composite was characterized by XRD, EDX and SEM. The synthesized composite was employed as photo catalyst for photo degradation of methyl orange. The photo degradation results showed that ZnO–TiO 2 exhibited better catalytic performance than ZnO and TiO 2 alone. The methyl orange photo degradation efficiency was determined to be 98, 75 and 60% over ZnO–TiO 2 , ZnO and TiO 2 respectively using 50 mL solution of 100 mg/L at 40 °C for 120 min. The ZnO–TiO 2 catalyzed photo degradation of methyl orange followed pseudo-first-order kinetic in terms of Langmuir–Hinshelwood mechanism.

The existing work emphasizes mainly to advance the low surface features of zinc oxide (ZnO) by dispersion of Fe 2 O 3 nanoparticles on the ZnO surface fabricated via a sol-gel route with Triton X-100 as a structure and capping agent to synthesis a novel series of Fe 2 O 3 /ZnO nanocomposites (NCs) with novel features assembling between the two nanoparticle materials. Fe 2 O 3 /ZnO is an effective semiconductor which has higher efficiency in the removal of numerous organic dyes and other pollutants. The NCs was characterized via HRTEM, XRD, FTIR, BET, RS and UV–Vis DRS. A photocatalytic performance of the fabricated Fe 2 O 3 /ZnO nanocomposites was estimated by continual degradation of the methylene blue dye (MB) as an organic pollutant in aqueous solution. The comparison between pure ZnO (NPs) and Fe 2 O 3 /ZnO (NCs) show advanced photocatalytic performance under both UV and sunlight irradiation. The impact of several parameters, for example, dopant contents, photocatalytic dosage, pH, chemical oxygen demand (COD) and point of zero charge (PZC) were evaluated and discussed. In addition, the protective species’ role was estimated via a radical scavenger route. The photo-degradation data shown that the Fe 2 O 3 /ZnO (10 wt%) semiconductor is the fit photocatalyst between the fabricated semiconductors for the methylene blue dye (MB) degradation. The intensity reduction peak of UV emission and the intensity increment of visible emission were led to the lessening in recombination between electrons and holes which are finally responsible for the maximum photocatalytic performance of Fe 2 O 3 /ZnO nanocomposites. The gained results confirmed that the dopant content is the major factor in photocatalytic degradation activity.

Biosorption is one of the effective technique for removal of metals from aqueous solutions/industrial effluents. Present work is aimed to use low cost and ecofriendly material to remove the iron metal from aqueous solution which could possibly be used at industrial level. For this purpose, Bougainvillea spectabilis leaves were used for the production of charcoal. This charcoal was activated using HCl and HNO 3 . The AC shows promising efficiency for the adsorption of Fe II as a function of medium pH, contact time, adsorbent dose and temperature. Maximum adsorption was observed with 0.5–0.9 g adsorbent dose, 30 min contact time and at pH 3. Adsorption showed independence of temperature in the range of 30–70 °C. Among, Freundlich and Langmuir isotherms, the adsorbate followed Langmuir isothermal model. Among kinetics models, adsorbate followed pseudo second order kinetic model with R 2 values of 0.9985 and 0.9996 for HCl treated and HNO 3 treated AC, respectively. These data suggest that AC synthesized from Bougainvillea leaves proved to be an excellent adsorbent for the removal of iron metal from aqueous solution.

Ginger oil in water (O/W) nanoemulsions, were produced using phase inversion composition method and Tween 80, as emulsifier. Effects of processing parameters namely, stirring rate (100 to1000 rpm) and water addition rate (1–10 mL/min) were evaluated on the physico-chemical, morphological, antioxidant and antimicrobial properties of the prepared O/W nanoemulsions using response surface methodology (RSM). Results indicated that well dispersed and spherical ginger nanodroplets were formed in the nanoemulsions with minimum particle size (8.80 nm) and polydispersity index (PDI, 0.285) and maximum zeta potential value (−9.15 mV), using stirring rate and water addition rate of 736 rpm and 8.18 mL/min, respectively. Insignificant differences between predicted and experimental values of the response variables, indicated suitability of fitted models using RSM. Mean particle size of the prepared nanoemulsion using optimum conditions were changed from 8.81 ± 1 to 9.80 ± 1 nm, during 4 weeks of storage, which revealed high stability of the resulted ginger O/W nanoemulsion. High antioxidant activity (55.4%), bactericidal (against Streptococcus mutans ) and fungicidal (against Aspergillus niger ) activities of the prepared nanoemulsion could be related to the presence of gingerols and shogaols, a group of phenolic alkanones, in the ginger oil, which those were detected by gas chromatography method.

To investigate the effect of additives urea and thiourea, on the micellization behavior of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), detailed conductance measurements were carried out in aqueous media at different temperatures. The critical micelle concentration (CMC), determined from the discontinuity in the plots of molar conductance versus square root of concentration, indicated an inhibitory effect of urea and thiourea on micelle forming ability of the surfactants SDS and CTAB in the range of composition studied. The demicellizing effect of urea has been found to be more pronounced in SDS than CTAB. These observations are further augmented by the evaluation of thermodynamic parameters of micellization. A negative change in enthalpy of micellization (ΔHm∘$\Delta{\text{H}}_{\text{m}}^{\circ}$) indicates a strong interaction between water and the additives and a positive change observed in entropy of micellization (ΔSm∘$\Delta{\text{S}}_{\text{m}}^{\circ}$) manifest, that the micellization is an entropy-driven process. Further ΔHm∘$\Delta{\text{H}}_{\text{m}}^{\circ}$ and ΔSm∘$\Delta{\text{S}}_{\text{m}}^{\circ}$ change in mutually compensating manner, so that ΔGm∘<0$\Delta{\text{G}}_{\text{m}}^{\circ} < 0$ is not significantly affected. Finally, the counterion binding values (β) obtained for SDS and CTAB remain practically constant from 0.6 to 0.8 between 25 °C and 45 °C indicate that the size and shape of micelle remain essentially constant. Moreover, the increase in ΔGII∘$\Delta{\text{G}}_{{\text{II}}}^{\circ}$ values, which represent the effect of co-solvent or additive on micellization, substantiates the above observations. Many early works has investigated the micellization behavior of surfactants using a fixed additive composition. However, in this study, variable aqueous compositions of urea (0.30–1.78 wt%) and thiourea (0.24–1.41 wt%) have been considered.

The aim of the present work is an approach towards the exploration of comprehension of rheological work on polymer composites synthesized by ex-situ dispersion of graphene oxide (GO) in poly(3-acrylamidopropyl trimethyl ammonium chloride (APTMACl) cationic hydrogel template. FTIR was carried out for confirmation of polymer synthesis and existence of GO in hydrogel network. The rheological investigation via frequency sweep curve (shear measurement) and oscillatory sweep (dynamic mechanical analysis) at different temperature 20, 25, 30, 35, 40 and 45 °C was performed. The storage (G′) and loss (G′′) moduli as a function of angular frequency, yield stress, tangent loss, damping factor and retention property were also studied to confirm the visco-elastomeric nature of the GO@p(APTMACl) composite and their semi solid response at different range of temperature. Various rheological models like Bingham model, modified Bingham model and Ostwald’s power law were applied. The temperature dependency was further tested via Arrhenius-Frenkel-Eyring equation. The sample showed best fitting in the modified Bingham model, which justified the pseudo plastic semi solid behavior of GO@p(APTMACl) composite within the linear visco-elastic region (LVER). All the properties from rheological study show best mechanical property and make the composite hydrogel good for drug delivery and for other environmental applications.

Density functional theory (DFT) studies were performed to evaluate the adsorption behavior and electronic response of (4,4) carbon nanotubes (CNTs) to the organophosphorus nerve agents 3,3-dimethylbutan-2-yl methyl phosphono fluoridate (Soman), pinacolyl methyl phosphonate (SOS), diethyl fluorophosphates (SAS-F) and diethyl chlorophosphate (SAS-Cl). The calculations were performed using the triple numerical plus polarization (TNP) as the basis set with an orbital cutoff of 4.5 Å. The electronic exchange and correlation effects were analyzed by generalized gradient approximation (GGA) with the BLYP parameterization. The studied systems were fully optimized and adsorption energy ( E ad ), interaction distances, geometric and electronic structures were investigated. According to the obtained relatively high E ad , it was shown that Soman, SOS, SAS-Cl and SAS-F more likely to be absorbed on the CNTs surfaces, introducing an interesting candidate for chemisorption of the nerve agent gas molecules. As a result, the order of increasing of the E ad values of the studied systems were | E ad SAS-F/CNT | > | E ad SAS-Cl/CNT | > | E ad SOS/CNT | > | E ad Soman/CNT | systems. The calculated partial density of states (PDOS) of the adsorption systems confirmed the strong electrons interaction between the nerve agent molecules and the CNTs surfaces. The obtained results indicated the potential application of CNTs in the design and fabrication of protective low-cost gas filters against toxic odorless nerve agent gases.

Sugarcane bagasse waste biomass (SBWB) efficacy for the adsorption of Zr(IV) was investigated in batch and column modes. The process variables i.e. pH 1–4 (A), adsorbent dosage 0.0–0.3 g (B), and Zr(IV) ions initial concentration 25–200 mg/L (C) were studied. The experiments were run under central composite design (CCD) and data was analysed by response surface methodology (RSM) methodology. The factor A, B, C, AB interaction and square factor A 2 , C 2 affected the Zr(IV) ions adsorption onto SBWB. The quadratic model fitted well to the adsorption data with high R 2 values. The effect of bed height, flow rate and Zr(IV) ions initial concentration was also studied for column mode adsorption and efficiency was evaluated by breakthrough curves as well as Bed Depth Service and Thomas models. Bed height and Zr(IV) ions initial concentration enhanced the adsorption of capacity of Zr(IV) ions, whereas flow rate reduced the column efficiency.