Systematic optimization of biochars derived from corn wastes, pineapple leaf, and sugarcane bagasse for Cu(II) adsorption through response surface methodology.

Many industrial wastewaters contain an appreciable amount of toxic copper (Cu(II)) that needs to be properly treated before discharging into receiving water body. Adsorption can effectively remove Cu(II) with optimized parameters. This study investigates the critical pyrolysis parameters of biochar derived from agricultural waste. Optimized biochar showed maximum Cu(II) adsorption capacity of 60.7, 36.8, and 35.5 mg g-1 by PLB, SBB, and CWB at pyrolysis temperatures of 555 ℃, 559 ℃, 507 ℃, respectively, compared with commercial activated carbon (CAC, 40.8 mg g-1). Surface characterization confirmed surface complexation, electrostatic interaction, and cation exchange capacity as Cu(II) removal mechanisms. The presence of humic acid reduced the Cu(II) removal of both CAC and optimized biochars. Optimized PLB displayed high reusability (87% Cu(II) removal efficiency) after five consecutive cycles using pressure cooker regeneration. With excellent Cu(II) adsorption capacity and reusability, the investigated biochars show high applicability potential to Cu(II)-laden wastewater treatment.

Adsorption of metal on pineapple leaf biochar: Key affecting factors, mechanism identification, and regeneration evaluation.

Although tremendous works have been done on metal adsorption via biochar, mechanisms responsible for metal adsorption remain uncertain. This is the first work that provides direct evidence on the identification of Ni(II), Zn(II), and Cu(II) adsorption mechanisms on pineapple leaf biochar (PLB) using surface characteristics analyses, including X-ray photoelectron spectroscope (XPS), Fourier transform infrared spectroscope (FTIR), and scanning electron microscope with energy-dispersive X-ray spectroscope (SEM-EDS). From Langmuir isotherm fitting, the maximum adsorption capacity of PLB for Ni(II), Zn(II), and Cu(II) are 44.88, 46.00, and 53.14 mg g-1, respectively, surpassing all biochars reported in the literature. Findings of surface characterization techniques coupled with cation released during adsorption, cation exchange, and surface complexation mechanisms were proposed. PLB is reusable and remains sufficient adsorption capacity even six consecutive cycles via pressure cooker regeneration. With high regenerability and ultrahigh adsorption capacity, PLB defines itself as a promising adsorbent for future applications in metal-laden wastewater.

The recovery of sulfuric acid from spent piranha solution over a dimensionally stable anode (DSA) Ti-RuO2 electrode.

Piranha solution is a highly acidic mixture of sulfuric acid and hydrogen peroxide. The present study aimed at developing a dimensionally stable anode (DSA), made of titanium metal foil coated with Ruthenium Dioxide (RuO2), for the electrochemical oxidation of hydrogen peroxide in the presence of strong sulfuric acid under ambient conditions. Results showed that hydrogen peroxide in the piranha solution was fully degraded in 5 h under a constant current of 2 A (or current density of 0.32 A-cm-2). The oxidation kinetics of hydrogen peroxide followed the Langmuir-Hinshelwood model. The observed rate constant was a function of applied current. The initial current efficiency was 17.5% at 0.5 A (or 0.08 A-cm-2) and slightly decreased to about 13.5% at applied current between 1.3 and 1.5 A (or current density of 0.208 and 0.24 A-cm-2). Results showed the capability and feasibility of the electrochemical oxidation process for the recovery of sulfuric acid from the spent piranha solution in semiconductor industrial installations or general laboratories.

Kinetic study and performance comparison of TiO2-mediated visible-light-responsive photocatalysts for the inactivation of Aspergillus niger.

Fungi are highly survived with exceptional resistance to environmental stress. Conventional fungicides are quite efficient, but the increase in use raises severe environmental problems. In this study, environmentally friendly TiO2-mediated visible-light-responsive photocatalysts, namely N-TiO2, N-T-TiO2, C-TiO2, and Pd-C-TiO2, were used to compare the performance of disinfecting a mold fungi Aspergillus niger. Key parameters, including photocatalyst dosage, the initial fungal concentration, and visible-light intensity, affecting the disinfecting process, was investigated. A new developed Light-responsive Modified Hom's (LMH) kinetic model incorporating visible-light intensity and photocatalyst light-absorption coefficient was firstly used to predict such photocatalytic process in fungal inactivation. Among the photocatalysts, Pd-C-TiO2 showed the highest inactivation performance against fungi, followed by C-TiO2, N-T-TiO2, and N-TiO2. In general, inactivation increased with increasing photocatalyst dosage and light intensity while decreased with increasing initial fungal concentration. For kinetic modeling, the LMH model supports the hypothesis that photocatalyst performance toward visible-light-driven fungal inactivation primarily depends on the light-absorption capacity of the photocatalyst. In conclusion, mold fungi Aspergillus niger are effectively disinfected by TiO2-mediated visible-light-responsive photocatalysts, and such fungal inactivation process could be predicted by LMH kinetic model.

Application of palladium-modified zeolite for prolonging post-harvest shelf life of banana.

BACKGROUND: The marketability of banana is limited by the rapid rate of ripening. However, the traditional post-harvest technologies may not be desirable. The aim of this study was to investigate the potential of a reusable material for the food preservation industry. RESULTS: The nanocomposite-based palladium (Pd)-modified zeolite (Pd/zeolite) was prepared by impregnating Pd into zeolite. Pd/zeolite had a Brunauer-Emmett-Teller dinitrogen specific surface area of 475 m2 g-1 with crystal structure similar to Y-zeolite. Transmission electron microscopy images showed the dispersion of Pd particles over the multi-pore zeolite support. Pd/zeolite uniquely acted as an adsorbent and a catalyst and was able to remove ethylene even after reaching breakthrough point. To prove Pd/zeolite is reusable, a 99 ± 0.8% ethylene removal efficiency still remained even after five consecutive cycles with repeated use of Pd/zeolite. The presence of Pd/zeolite significantly decreased the ethylene concentration during 18 days of storage at 20 ± 2 °C. CONCLUSIONS: Pd/zeolite could delay the ripening of banana and improve its firmness and the peel color significantly. Findings indicated that the as-prepared Pd/zeolite is an effective adsorbent/catalyst with high potential for practical application in ethylene removal, especially for the post-harvest period. © 2019 Society of Chemical Industry.

Adsorption characteristics of ammonium ion onto hydrous biochars in dilute aqueous solutions.

This research aims at studying the characteristics of ammonium adsorption onto hydrous bamboo biochar. Results showed that pH played the most important role in ammonium adsorption. High ionic strength enhanced the ammonium adsorption capacity of bamboo biochar. Ammonium adsorption was exothermic and spontaneous. FTIR results showed shift, disappearance, or appearance of specific functional groups on the bamboo biochar surface. Surface precipitation and complex formation contributed to the adsorption of ammonium onto hydrous bamboo biochar. Biochar can be an effective adsorbate for ammonium removal from water. Additionally, the formation of nitrogen containing precipitates on the biochar surface, potentially, leads to the in-situ synthesis of slow-release fertilizer.

Hyperspectral sensing for turbid water quality monitoring in freshwater rivers: Empirical relationship between reflectance and turbidity and total solids.

Total suspended solid (TSS) is an important water quality parameter. This study was conducted to test the feasibility of the band combination of hyperspectral sensing for inland turbid water monitoring in Taiwan. The field spectral reflectance in the Wu river basin of Taiwan was measured with a spectroradiometer; the water samples were collected from the different sites of the Wu river basin and some water quality parameters were analyzed on the sites (in situ) as well as brought to the laboratory for further analysis. To obtain the data set for this study, 160 in situ sample observations were carried out during campaigns from August to December, 2005. The water quality results were correlated with the reflectivity to determine the spectral characteristics and their relationship with turbidity and TSS. Furthermore, multiple-regression (MR) and artificial neural network (ANN) were used to model the transformation function between TSS concentration and turbidity levels of stream water, and the radiance measured by the spectroradiometer. The value of the turbidity and TSS correlation coefficient was 0.766, which implies that turbidity is significantly related to TSS in the Wu river basin. The results indicated that TSS and turbidity are positively correlated in a significant way across the entire spectrum, when TSS concentration and turbidity levels were under 800 mg·L(-1) and 600 NTU, respectively. Optimal wavelengths for the measurements of TSS and turbidity are found in the 700 and 900 nm range, respectively. Based on the results, better accuracy was obtained only when the ranges of turbidity and TSS concentration were less than 800 mg·L(-1) and less than 600 NTU, respectively and used rather than using whole dataset (R(2) = 0.93 versus 0.88 for turbidity and R(2) = 0.83 versus 0.58 for TSS). On the other hand, the ANN approach can improve the TSS retrieval using MR. The accuracy of TSS estimation applying ANN (R(2) = 0.66) was better than with the MR approach (R(2) = 0.58), as expected due to the nonlinear nature of the transformation model.