The effective adsorption of tetracycline onto zirconia nanoparticles synthesized by novel microbial green technology.

Pseudomonas aeruginosa bacteria have been used in this study for zirconia nanoparticles synthesis through green technology for adsorption driven bioremediation of tetracycline from wastewater. The characterization of synthesized nano zirconia has been performed by employing dynamic light scattering, field emission-transmission electron microscopy, energy dispersive X-ray, X-ray diffraction, fourier transform infrared spectroscopy, and point of zero charge analysis. The zirconia nanoparticles have shown average particle size ~15 nm, monoclinic and tetragonal crystal structure with 6.41 nm of crystallite size, the presence of elemental zirconium and oxygen, and the occurrence of functional groups like O-Zr-OH, Zr-O-Zr and Zr-O bonds. The zirconia nanoparticles mediated adsorption of tetracycline has been found to be effective at solution pH 6.0 and in a very less contact time 15 min. Strong electrostatic interaction between zwitterionic form of tetracycline and protonated surface of zirconia nanoparticles is the governing adsorption mechanism in this study. The kinetic study has been performed on the basis of the tetracycline adsorption process revealing that the adsorption phenomenon follows pseudo-second order kinetic, further suggesting chemisorption of tetracycline over zirconia nanoparticles. The Langmuir isotherm model has been found to be the best fitted model among the all isotherm models indicating the involvement of monolayer uptake of tetracycline on the surface of zirconia nanoparticles. Moreover, the maximum tetracycline adsorption capacity of zirconia nanoparticles calculated by the Langmuir isotherm model is close to 526.32 mg/g. This finding is quite reasonable to accept that zirconia nanoparticle may be used as an alternative adsorbent to mitigate the tetracycline contamination in wastewater.

Synthesis of MnFe2O4 and Mn3O4 magnetic nano-composites with enhanced properties for adsorption of Cr(VI): artificial neural network modeling.

This study reports adsorptive removal of Cr(VI) by magnetic manganese ferrite and manganese oxide nano-particles (MnF-MO-NPs) composite from aqueous media. The X-ray diffraction pattern of MnF-MO-NPs revealed a polycrystalline nature with nanoscale crystallite size. The prepared adsorbent with high Brunauer-Emmett-Teller specific surface area of 100.62 m2/g and saturation magnetization of 30.12 emu/g exhibited maximum Cr(VI) removal at solution pH 2.0 and was easily separated from water under an external magnetic field. Adsorption capacity as much as 91.24 mg/g is reported and electrostatic interaction between positively charged adsorbent surface and anionic metal ion species is the main driving force in this adsorption. Adsorption experimental data followed Langmuir isotherm and second order kinetics. Partial involvement of intra-particle diffusion was also observed due to the mesoporous nature of MnF-MO-NPs. The thermodynamic studies revealed that the process was favorable, spontaneous and exothermic in nature. An artificial neural network model was developed for accurate prediction of Cr(VI) ions removal with minimum mean squared error (MSE) of 15.4 × 10-4 and maximum R2 of 0.98. Owing to large surface to volume ratio, advantage of easy magnetic separation, and high adsorption capacity towards Cr(VI), the reported MnF-MO-NPs appear to be a potential candidate in Cr(VI) contaminated wastewater remediation.

Boosted sono-oxidative catalytic degradation of Brilliant green dye by magnetic MgFe2O4 catalyst: Degradation mechanism, assessment of bio-toxicity and cost analysis.

The magnetic MgFe2O4 nanoparticles (NPs) were fabricated via a facile co-precipitation technique and was comprehensively characterized by XRD, FTIR, SEM, EDX and VSM. The prepared NPs were used as catalyst in presence of ultrasound (US) irradiation to activate persulfate (PS) for generation of sulfate radicals (SO4·-) for boosted degradation of toxic Brilliant Green (BG) dye. Preliminary experiments revealed that highest BG dye degradation efficiency of 91.63% was achieved at MgFe2O4 catalyst dose of 1.0 g/L, PS dose of 300 mg/L, and initial dye concentration of 70 ppm within 15 min of US irradiation. However, only US, US in presence of PS oxidation and US in presence of MgFe2O4 catalyst have shown 20.2%, 83.6% and 45.0% of BG dye removal, respectively. Furthermore, response surface methodology (RSM) based central composite design (CCD) was executed to investigate the effect of interaction between independent variables such as MgFe2O4 catalyst dose (0.5-1.5 g/L), PS dose (150-350 mg/L), initial BG dye concentration (50-150 ppm) and US irradiation time (4-12 min). The RSM based quadratic model was used to predict the experimental data, and the prediction accuracy was confirmed by analysis of variance (R2 = 0.98). The established RSM model has predicted the optimum experimental conditions as MgFe2O4 catalyst dose of 0.75 g/L, PS dose of 300 mg/L, initial dye concentration of 75 ppm and sonication time of 10 min. Subsequently, the treatment cost analysis was performed for all thirty experimental runs of CCD, and the RSM predicted response was found to be evidently optimum as this has delivered best economic condition (140 $/kg of BG removed) with respect to relative dye removal (%). COD removal and residual sulfate analysis have demonstrated satisfactory reduction of COD (90.31%) as well as sulfate ions (42.87 ppm) in the dye solution after treatment. Results of degradation pathway analysis portrayed the transformation of BG molecule (M/Z ratio 385) into simpler fractions with M/Z ratio of 193, 161, 73, and 61. Moreover, the toxicity analysis revealed that sono-catalytically activated PS system has efficiently reduced the toxicity level of BG dye from 93.9% to 5.13%.

Mature landfill leachate treatment using sonolytic-persulfate/hydrogen peroxide oxidation: Optimization of process parameters.

The suitability of stand-alone ultrasound (US) system, coagulation pre-treatment followed by US, hydrogen peroxide added US system (US-H2O2) and persulfate added US system (US-PS) for the treatment of matured landfill leachate was investigated. With US system, around 67% COD removal and an increase in BOD/COD ratio were observed (from 0.033 to 0.142) after 15 min at 30% US amplitude. However, the energy input required for landfill leachate treatment in US system was found to be very high due to the presence of fixed solids. Coagulation pretreatment using alum was carried out to improve the overall COD removal and reduce the cost of treatment. As a result, the COD removal was increased to 78% (42% in pretreatment and 36% in US) in 15 min. On the other hand, US-H2O2 and US-PS hybrid systems have shown significant improvement in COD removals (93% and 86%, respectively) from raw leachate after 15 min. Subsequently, a three factor (i.e. PS dose (mg/L), H2O2 dose (mol/L), and US amplitude (%)) 5-level design of experiment was used to maximize the COD removal efficiency by response surface methodology (RSM). The RSM model generated a quadratic equation to accurately analyze the influence of input variables on COD removal efficiency (R2 of 0.92). A maximum COD removal of 98.3% was predicted using the model and the corresponding optimal experimental condition were identified as follows: PS dose ∼4700 mg/L, H2O2 dose ∼0.7 mol/L and US amplitude ∼49%. The overall observations reveals that PS and H2O2 coupled with US system has a great prospective to treat mature landfill leachate.

Ultrasonic assisted enhanced adsorption of methyl orange dye onto polyaniline impregnated zinc oxide nanoparticles: Kinetic, isotherm and optimization of process parameters.

The fabrication of novel functionalized composite materials as adsorbent is considered to be the core research area in adsorption technology for environmental applications. Indiscriminate disposal of industrial effluents containing toxic dyes has become a serious environmental issue across the globe since last few decades. In view of above, this study focused on the performance evaluation of ZnO/polyaniline nanocomposite (ZnO-PANI-NC) for quick ultrasonic assisted adsorptive remediation of methyl orange dye from aqua matrix. ZnO nanoparticles were fabricated by a simple co-precipitation method and ZnO-PANI-NC was synthesized by in situ oxidative polymerization of aniline monomer in presence of ZnO nanoparticles. The nanocomposite was extensively characterized for its crystalline nature, morphological characteristics, surface chemical bonding, specific surface area and pore volume by employing XRD, SEM, TEM, FTIR, and BET analysis. The ZnO-PANI-NC has shown superior adsorptive performance as compared to pure PANI as well as ZnO nanoparticles and the maximum monolayer adsorption capacity of 240.84 mg/g was obtained for the ZnO-PANI-NC. Under ultrasonic environment the adsorption reaction reached to equilibrium (more than 98% MO dye removal) within 15 min of reaction. Adsorption process followed Langmuir isotherm model and second order kinetic model strictly and contribution of intra-particle diffusion was also observed. The ZnO-PANI-NC has shown its high regeneration ability (more than 86%) even after 5th consecutive cycles of adsorption-desorption. Response surface methodology based optimization was used to optimize the adsorption experimental data and maximum MO removal of 99.12% was observed at optimum sonication time 13 min, adsorbent dose 0.38 g/L and initial MO concentration at 28 mg/L.