Initial Reaction pH Research Articles

Peningkatan pH dengan Pemberian Bahan Organik pada Pengelolaan Air Asam Tambang Menggunakan Metode Passive Treatment

Mining is the process of extracting beneficial minerals from the surface of the earth that have an impact on the formation of acid mine drainage (AMD). One method of passive AMD management is passive treatment. This study used the Nested Factorial Experiment Design method. The types of organic matter used were empty fruit bunch oil palm (EFB) and cow dung, with doses of 0 Mg ha-1 (control), 50 Mg ha-1, 100 Mg ha-1, 150 Mg ha-1 and 200 Mg ha-1. Each treatment was three repeats so that 30 units of experimental units were obtained. The pH value of AMD in the untreated (control) reactor was 3.67. The initial reaction (pH) of AMD (0 days) with EFB application at a dose of 50 – 200 Mg ha-1 ranged from 3.63 – 4.28 and the initial pH of cow dung was 3.84 – 4.13. The reaction (pH) of the 1st to 4th weeks of AMD after adding EFB organic matter at a dose of 50 – 200 Mg ha-1 show a pH range (6.38 – 7.59) and cow manure at a dose of 150 – 200 Mg ha-1 show a pH (6.09 – 7.01). The conclusion are that the application of EFB organic matter on constructed wetland media for 4 weeks had a very real effect on increasing the pH of the AMD dose of 100 – 200 Mg ha-1 while cow dung 150 – 200 Mg ha-1 are the most effective against increasing pH.

Hydrothermal-assisted synthesis of Sr-doped SnS nanoflower catalysts for photodegradation of metronidazole antibiotic pollutant in wastewater promoted by natural sunlight irradiation.

In this study, we report a facile hydrothermal synthesis of strontium-doped SnS nanoflowers that were used as a catalyst for the degradation of antibiotic molecules in water. The prepared sample was characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible absorption spectroscopy (UV-Vis). The photocatalytic ability of the strontium-doped SnS nanoflowers was evaluated by studying the degradation of metronidazole in an aqueous solution under photocatalytic conditions. The degradation study was conducted for a reaction period of 300 min at neutral pH, and it was found that the degradation of metronidazole reached 91%, indicating the excellent photocatalytic performance of the catalyst. The influence of experimental parameters such as catalyst dosage, initial metronidazole concentration, initial reaction pH, and light source nature was optimized with respect to metronidazole degradation over time. The reusability of the strontium-doped SnS nanoflowers catalyst was investigated, and its photocatalytic efficiency remained unchanged even after four cycles of use.

Facile design and fabrication of RP/ZnIn2S4 composite photocatalysts with efficient removal of antibiotics under visible-light irradiation

Efficient photocatalysts with visible light irradiation have a bright future in practical environmental remediation. ZnIn2S4 is a promising environmentally friendly visible-light photocatalyst, due to its appropriate narrow band gap and excellent chemical stability. In this research, the RP/ZnIn2S4 composites with flower spheroidal morphology were synthesized by loading RP onto the surface of ZnIn2S4 via a one-pot hydrothermal process. The experimental results show that the tetracycline (TC) degradation efficiency of RP(1 wt%)/ZnIn2S4 was up to 85.1 %, compared with pure RP, ZnIn2S4, and other series of RP/ZnIn2S4 composites. The optimal degradation conditions were as following: 1 wt% RP modification amount, 30 mg catalyst amount, 30 mg/L initial TC solution concentration, and the initial reaction pH of 7. At the same time, good repeatability and stability of RP(1 wt%)/ZnIn2S4 toward TC removal confirm its potential value for practical applications. In addition, the degradation efficiency of RP(1 wt%)/ZnIn2S4 for rifamycin and ofloxacin under the similar conditions was 80.2 % and 65.3 %, respectively, indicating the universal application of RP/ZnIn2S4 for degradation of different antibiotic pollutants. The possible photocatalytic mechanism was proposed based on the trapping experiment and ESR test. The RP(1 wt%)/ZnIn2S4 composite photocatalytic materials with high efficiency and stability are expected to contribute to the exploration of the environmental protection field.

Characteristics and anti-inflammatory effects of the enzymatically extracted polysaccharides of Sargassum fulvellum using crude enzyme from Shewanella oneidensis PKA 1008

Alginic acid is a polysaccharide obtained from brown algae, and its oligosaccharide has various functions such as antiviral, antitumor, immunoregulation, and antioxidant. However, because of its high viscosity, numerous studies have degraded the alginic acid by enzymes to improve its utilisation. In the present work, we characterised Sargassum fulvellum enzymatic extract (SFEE) using polysaccharide-degrading enzyme obtained from Shewanella oneidensis PKA 1008, and investigated its anti-inflammatory potential. S. fulvellum powder and crude enzyme were mixed at a ratio of 1:1 (v/v), and reacted at 30°C for 0 - 48 h to obtain the optimum degrading time. The changes in pH, colour, reducing sugar, and viscosity of SFEE were determined. The anti-inflammatory activity of SFEE was confirmed by measuring the expression level of nitric oxide (NO) and pro-inflammatory cytokines (IL-6, TNF-α, and L-1β) in RAW 264.7 macrophage cell line. The reducing sugar content was found to increase 2.75-fold at 24 h as compared to that at the initial reaction point, but pH and viscosity decreased significantly with increasing reaction time. SFEE showed a high inhibitory effect on the levels of NO and pro-inflammatory cytokines. SFEE thus has great potential for development as a functional food and therapeutic material owing to its anti-inflammatory effect.

Synthesis of mesoporous silica using a mineral silica source

AbstractMesoporous silica has been applied in catalysis, separations, and drug delivery. It has generally been made using organosilicon precursors such as tetraethyl orthosilicate. For sustainability, it is necessary to find readily accessible mineral sources for making mesoporous silica. In this work, we demonstrate the successful synthesis of mesoporous silica with 10 nm average pore size using the mineral forsterite (Mg2SiO4) as a silica source, providing a potentially cheaper and more Earth‐friendly route to making technologically important porous silica materials. Pure forsterite was synthesized by a solid‐state chemistry route at 1000°C and underwent dissolution–reprecipitation in aqueous hydrochloric acid containing the soft template surfactant, Pluronic P123. Variations of initial reaction pH (−0.2 to 0.6), reaction time (12–24 h), reaction temperature (50 to 90°C), and silica precursor (forsterite and fumed silica) were performed. The mesoporous silica aged at 70°C for 24 h had the highest porosity, with a surface area of 735 m2/g and a pore volume of 1.4 ml/g, comparable to mesoporous silica made using conventional starting materials. This novel geomimetic synthesis route supports the possibility of analogous formation of structured (mesoporous or zeolitic) silica in nature under abiotic or prebiotic conditions.

Magnesium-modified biochar was used to adsorb phosphorus from wastewater and used as a phosphorus source to be recycled to reduce the ammonia nitrogen of piggery digestive wastewater

High concentrations of ammonia nitrogen in piggery digestive wastewater are toxic to the microorganisms in wastewater treatment systems. The ammonia nitrogen load can be decreased by struvite precipitation. The purpose of this paper was to take phosphate from magnesium-modified biochar adsorbed wastewater as a phosphorus source and add it to biogas slurry to reduce the ammonia nitrogen concentration . The effects of phosphorus source dosage, initial reaction pH value and reaction time on ammonia nitrogen removal from biogas slurry were investigated, and then the subsequent biogas slurry underwent sequencing batch reactor biochemical treatment. When the phosphorus source dosage was 20 g/L, initial reaction pH value was 10.0 and reaction time was 1 h, the NH 3 –N recovery was 62.98%. The subsequent biogas slurry met the discharge standards (DB44/613–2009) after biochemical treatment. An innovative process for the recycling of pig farm waste, nitrogen and phosphorus recovery and advanced treatment of biogas slurry is first proposed in this paper. • Mg@C was prepared by pyrolysis of pig manure and waste residue containing magnesium. • Mg@C adsorbed PO 4 3− from SBR effluent as a phosphorus source for MAP reaction. • After MAP reaction, the NH 3 –N concentration in biogas slurry was below 200 mg/L. • After MAP reaction, SBR effluent more easily met the discharge standard than CK.

Rapid detoxification of Microcystin-LR by selective catalytic hydrogenation of the Adda moiety using TiO2-supported Pd catalysts

The hepatotoxicity of Microcystin-LR (MC-LR) is mainly caused by its Adda moiety. In this study, we used TiO2-supported Pd catalysts to selectively hydrogenate the CC bonds in the Adda moiety, achieving rapid detoxification of MC-LR in water under ambient conditions. MC-LR was removed within 5 min by catalytic hydrogenation on Pd(1.0)/TiO2 with a catalyst dosage normalized rate constant of 1.3 × 10−2 L mgcat−1 min−1, significantly more efficient than other catalytic treatment methods. The reactions proceeded in a highly selective manner towards catalytic hydrogenation at the CC bond of the Mdha moiety and subsequently the conjugated double bond of the Adda moiety, yielding two intermediates and one final product. Upon catalytic hydrogenation for 30 min on Pd(0.07)/TiO2, the toxicity of MC-LR (assessed by protein phosphatase 2A activity assay) drastically decreased by 90.8%, demonstrating effective detoxification. The influence of catalyst support, Pd content, initial MC-LR concentration, reaction pH, and catalytic stability were examined. Surface adsorption and the cationic Pd played a crucial role in the reaction kinetics. Our results suggest that catalytic hydrogenation is a highly effective and safe strategy for detoxifying MC-LR by selective reactions.

Eco-friendly approach for efficient catalytic degradation of organic dyes through peroxymonosulfate activated with pistachio shell-derived biochar and activated carbon

ABSTRACT This study introduces a simple method for the preparation of biochar (BCP) and activated carbon using pistachio (ACP) external hull as residual solid waste. Low-cost raw materials, biodegradable, recyclable and organic solid wastes are advantages of this method. Furthermore, complete degradation of methyl orange (MO) and methylene blue (MB) to H2O and CO2 as eco-friendly compounds in mild reaction condition occurs at a short time. Also, the effects of crucial parameters (temperature, time, catalyst dosage, initial dye and oxidant concentration, initial reaction pH level and radical scavengers), capability, adaptability, performance and reusability of ACP were also evaluated. The results displayed that dyes could be decomposed effectively by the PMS/ACP-800 system. Furthermore, the sulphate radical () was a major active role in the degradation process, while hydroxyl radical ( • OH) played a minor role. Overall, ACP had yielded high degradation of MB and MO dyes; therefore, ACP-800 could be effectively and reliably applied in the treatment of industry effluents containing MB and MO dyes.

Comparative study of acid mine drainage using different neutralization methods

Abstract Two-stage acid mine drainage (AMD) neutralization residue yield is 2.57 t/t acid equivalent using limestone and lime, 15.74% less than the 3.05 t/t acid equivalent yield from single-stage lime neutralization residue. XRD results shows that the main residue component generated by two-stage neutralization is CaSO4•0.5H2O, with a molecular weight 15.70% lower than the CaSO4•2H2O generated in single-stage neutralization. The differing amount of gypsum crystallization water from the different neutralization processes is the main cause of the different residue yields. While the actual removal rate and pH of Fe3+ are consistent with the theory, those for Zn2+, Cu2+ and Al3+ are inconsistent with the theoretical values, the error rate increasing with increasing pH. Co-precipitation with and adsorption by Fe(OH)3, mainly generated during neutralization, are the main reasons for the difference. The cost of two-stage neutralization is 16.60% less than that of single-stage neutralization when the initial reaction pH is 3.4, but the unit cost begins to increase if the initial reaction pH is raised above 3.4. When the initial pH is 4.0, the cost of two-stage neutralization exceeds that of single-stage neutralization by 4.07%.

Highly efficient electro-catalysis activationof peroxymonosulfate by “used” As/Cr/Mo@FeOOH material for the degradation of metronidazole: Degradation mechanism and toxicity assessment

Peroxymonosulfate (PMS) activation have provided a new direction to eliminate the organic pollutant. Current challenges that must be solved include secondary pollution by the metal ions and limitation in the recyclability of the catalysts. The waste 1D-FeOOH adsorbent with adsorption of metal elements (As, Cr or Mo ions) has been reused as an efficient electro-catalyst for PMS activation and used to metronidazole (MTD) degradation for the first time. The effects of current density, initial reaction pH, stirring rate, PMS dosage and solution temperature on MTD degradation was studied. The used 1D-FeOOH with adsorption of Mo ions showed the highest PMS activation ability and 99.6% MTD could be removed after 30 min degradation. The •OH and Found that SO4•− is the main free radical for MTD degradation. DFT calculation and characterization results were demonstrated that the high PMS electro-catalysis activation ability of the 1D-FeOOH@Mo has resulted from the special composition-dependent interactions among FeOOH@Mo and PMS, including stable adsorption properties, easy electron transfer and weak OO bond. The possible PMS electro-catalysis activation mechanism and MTD degradation pathway have been proposed. (ECOSAR) was used to evaluate the toxicity of metronidazole during degradation. The results showed that the toxicity of MTD and its intermediates could be effectively reduced by prolonging the degradation time in 1D-FeOOH@Mo solution. This work provides new insights for waste adsorbent disposal and gives a new perspective for PMS activation to degradation of antibiotics in water.

Photodegradation of tartrazine dye favored by natural sunlight on pure and (Ce, Ag) co-doped ZnO catalysts.

In this work, the synthesis of pure and (Ce, Ag) co-doped ZnO was successfully accomplished using a solvothermal process. The synthesized samples were characterized by ultraviolet-visible spectroscopy, X-ray diffraction, and scanning electron microscopy. The photocatalytic ability of the samples is estimated through degradation of tartrazine in aqueous solution under photocatalytic conditions. The degradation study carried out for a reaction period of 90 min at and a free pH = 6.0 found that dye degradation is 44.82% for pure ZnO and 98.91% for (Ce, Ag) co-doped ZnO samples, indicating its excellent photocatalytic ability. Tartrazine mineralization was also studied by calculating the degradation of chemical oxygen demand. The effect of operating parameters such as catalyst dose, initial concentration of tartrazine, initial reaction pH, and nature of light source has been optimized for tartrazine degradation as a function of time. The reusability of ZnO and (Ce, Ag) co-doped ZnO catalysts was studied and its photocatalytic efficiency was found to be unchanged, even after six cycles of use. The mechanism of photocatalytic activity was also proposed.

New insight into increased toxicity during ozonation of chlorophenol: The significant contribution of oxidizing intermediates

Biological safety evaluation and toxic by-products identification are critical issues in the partial oxidation process. Previous studies have shown that the whole toxicity increased in the effluent of an ozonation process for chlorophenols removal. Here, this study systematically investigated the changes of acute toxicity during the ozonation of 3-chlorophenol under four key operational conditions, including initial 3-chlorophenol concentration (20–60 mg/L), ozone concentration (14–42 mg/L), reaction pH (3−10) and ozonation time (0–50 min). The results found that the ozonation process induced a significant increase in the acute toxicity, followed by its gradual decrease. The observation of higher acute toxicity increase generally happened at higher initial 3-chlorophenol concentration, lower ozone concentration and lower reaction pH. At the toxicity peaks, the oxidizing intermediates posed acute toxicity equal to 65.8%–96.3% of the whole toxicity. Among them, free active chlorine (FAC) contributed 21.4%–51.6%, and its concentrations significantly correlated to the acute toxicity change. Therefore, two possible FAC generation pathways initiated by ozone molecule were proposed: (i) bond breaking of the oxychloride complex formed by the combination of chloride ion and zwitterion; or (ii) hydrolysis of ozonides formed by the electrophilic reaction of ozone molecule. Together, these results firstly revealed the significant toxicity contribution of oxidizing intermediates during the ozonation of chlorophenols, supporting further development of safe and effective ozone-based water treatment schemes.

The effect of hybrid zinc oxide/graphene oxide (ZnO/GO) nano-catalysts on the photocatalytic degradation of simazine

The photocatalytic degradation of simazine (SIM) was investigated using zinc oxide/graphene oxide (ZnO/GO) composite materials under visible light irradiation. The reaction kinetics was studied to optimize the reaction parameters for efficient degradation of SIM. Batch studies were performed to investigate the effects of initial reaction pH, the loading of the ZnO onto GO, and mass of catalyst on the removal of SIM from aqueous solution. A pH of 2 was determined to be the optimal reaction pH for the different ZnO-loaded GO catalysts. In addition, a mass of 40 mg of catalyst in the reaction was observed to be the most effective for the catalysts synthesized using 20 and 30 mmol of Zn2+ ions; whereas a mass of 10 mg was most effective for the ZnO/GO composite material synthesized using 10 mmol Zn2+ ions. The reaction was observed to follow a second-order kinetics for the degradation process. Furthermore, the synthesized ZnO/GO composite catalysts resulted in higher reaction rates than those observed for pure ZnO. The 30 mmol ZnO/GO composite expressed a rate of SIM degradation ten times greater than the rate observed for pure ZnO, and sixty-two times greater than the rate of photolysis. In addition, the catalyst cycling exhibited a constant photocatalytic activity for the ZnO/GO composite over three reaction cycles without the need of a conditioning cycle.

Antioxidant properties of aqueous selenium nanoparticles (ASeNPs) and its catalysts activity for 1, 1-diphenyl-2-picrylhydrazyl (DPPH) reduction

In this work, Aqueous selenium nanoparticles (ASeNPs) was prepared from sodium selenite (Na2SeO3) as a precursor by using gallic acid (GA) as a reducing agent in wet chemical methods. The morphology, particle size, structure, and free radical scavenging (FRS) activity of ASeNPs were characterized by high-resolution transmission electron microscopy (HRTEM), ultraviolet–visible spectroscopy (UV–vis), fourier transform infrared (FTIR), energy-dispersive X-ray spectroscopy (EDAX), dynamic light scattering (DLS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Synthesized ASeNPs showed uniform sphere-shaped with an average particle size range of 98 nm. EDAX analysis confirmed the existence of selenium in the nanosphere. FTIR results show that hydroxy (-OH), carboxyl (-CO), alkyl (C–H) functional groups on the surface of ASeNPs. The percent scavenging of DPPH of ASeNPs for initial reaction pH 6, 6.5, 7 and buffer 7 was obtained as 80.6%, 84.0%, 83.0% and 73.0% respectively. The DPPH radical scavenging activity of ASeNPs without using any stabilizer and capping agent in this work reached higher than 80% in 1.0 ml of ASeNPs. The percent scavenging of ABTS of ASeNPs for initial reaction pH 6, 6.5, 7 and buffer 7 was obtained as 85.7%, 94.9%, 93.8%, and 75.1% respectively. Apparent rate constant (kapp) for FRS reactions of DPPH increases linearly with an increasing concentration of ASeNPs, an increase in the kapp value was because of the accessibility of more interaction sites of ASeNPs.

A novel double Z-scheme photocatalyst Ag3PO4/Bi2S3/Bi2O3 with enhanced visible-light photocatalytic performance for antibiotic degradation

In this study, the novel visible light double Z-scheme photocatalysts (Ag3PO4/Bi2S3/Bi2O3) were synthesized by the facile means. The crystal texture, chemical states, morphology and optical characteristics of prepared photocatalysts were investigated by XRD, FTIR, XPS, SEM, TEM, N2 adsorption-desorption analysis, UV–vis DRS, and PL etc. techniques, respectively. Meanwhile, the band structures and the density of states of three single-phase semiconductor and Ag3PO4/Bi2S3/Bi2O3 (ABB) composite had been calculated by Materials Studio program based on density functional theory. For assessing the photocatalytic performance of these samples, the visible light photodegradation of antibiotics sulfamethazine (SAZ) and cloxacillin (CLX) were performed. The effects of initial antibiotic concentration, reaction pH, supporting electrolyte and surfactant on photocatalytic performance were all investigated. The results indicated that the ABB-3 composite exhibited higher photocatalytic performance than other comparison samples. Furthermore, four cycle experiments confirmed the ABB-3 composite also exhibited satisfactory photostability. The scavenger tests and ESR data demonstrated that the active species h+, O2−, and OH worked together in the photocatalytic process, and the h+ and O2− play a more important role than OH. All in all, the increased photocatalytic performance of ABB composite could owe to the photosensitization of Bi2S3 and the double Z-scheme photocatalytic system. This study could inspire some new idea for building the novel and efficient heterogeneous photocatalysts and benefiting their practical application.

An environmentally friendly hydrothermal method of vanadium precipitation with the application of oxalic acid

During the traditional metallurgical process of vanadium (V), an ammonium salt is often employed as the precipitator to form an ammonium vanadate, which converted into V2O5 in the subsequent calcination. Due to the restriction of ammonia emissions by the Chinese government, the vanadium-bearing shale industry in China urgently needs to find out a new environmentally friendly vanadium precipitation method. As the widely used method in the synthesis of VO2, hydrothermal reduction with oxalic acid was firstly introduced into vanadium precipitation in this study. Several factors that affect the vanadium precipitation were studied in the batch tests, such as initial reaction pH, temperature, time, and n(H2C2O4·2H2O)/n(V(V)). A product with 99.53% purity of VO2(B) and 99.47% extent of vanadium precipitation was obtained under the optimized reaction conditions: initial reaction pH of 0.80, time of 8 h, temperature of 493 K, and n(H2C2O4·2H2O)/n(V(V)) of 1.00. Raman spectroscopy, inductively coupled plasma with optical emission spectrometry (ICP-OES) and scanning electron microscopy with energy dispersive spectroscopy (SEM-EDS) were also carried out to characterize the product and the results indicated that the product was pure VO2(B) in the form of nanorods. The reaction mechanism of VO2 prepared from stripped vanadium solution is put forward and the transformation of V from stripped vanadium solution to VO2 is proposed as: VO2+ → VO2(C2O4)− → VOC2O4 → VO2. Overall, the present hydrothermal method of vanadium precipitation with the application of oxalic acid has the characteristics of environmentally friendly, short process, simple and efficient.

Highly efficient activation of peroxymonosulfate by natural negatively-charged kaolinite with abundant hydroxyl groups for the degradation of atrazine

In this study, natural kaolinite, an abundant, low cost, thermally and chemically stable, and easily recyclable material was evaluated for the performance to activate peroxymonosulfate (PMS) by the degradation of atrazine. Based on radical quenching experiments and electron spinning resonance (ESR) spectra, hydroxyl radical (OH) and sulfate radical (SO4−) were identified to be the primary reactive species. The effects of catalyst loading, initial reaction pH, PMS dosage, initial atrazine concentration, and the presence of inorganic ions (Cl−, NO3−, HCO3− and H2PO4−) were also investigated in this work. Interestingly, the presence of H2PO4− enhanced the degradation efficiency of atrazine via promoting the decomposition of PMS. The transformation products were detected on a quadrupole time-of-flight liquid chromatography/mass spectrometer (Q-TOF-LC-MS) and the possible degradation pathway of atrazine was proposed. Based on comprehensive characterizations of crystal phase and crystallinity, porosity and pore structure, surface morphology, functional groups, and valence state of specific elements, the catalytic ability of natural kaolinite towards PMS is attributed to the abundant surface-bonded and structural hydroxyl groups. This study provides new insights of PMS activation by natural minerals for the degradation of refractory and deleterious contaminants in wastewater treatment.

A novel carbon-coated Fe-C/N composite as a highly active heterogeneous catalyst for the degradation of Acid Red 73 by persulfate

A magnetic carbon-coated Fe-C/N composite was synthesized by a simple impregnation method and its performance in activating persulfate (PS) to degrade Acid Red 73 (AR 73) was investigated. The as-prepared carbon-coated Fe-C/N hybrid material was characterized via transmission electron microscopy, Raman spectra, X-ray diffraction and X-ray photoelectron spectrum. Degradation experiments showed that 98.11% of AR 73 could be degraded in 10 min, but its COD was partly removed. The effects of initial reaction pH and temperature were also evaluated. An increase of temperature was beneficial for the removal of AR 73, while the increase of pH had an opposite result. The activation energy of the AR 73 degradation was determined to be 46.12 KJ/mol, smaller than those in relative literatures. The recycling test showed that the carbon-coated Fe-C/N composite had good stability. The mechanism study indicated that the catalytic performance of Fe-C/N was due to the synergistic effect between Fe3C and Fe3N, and the N doped carbon shell suppressed the rate of Fe leaching, thus enhancing its stability.

PH-Controlled Assembly of 3D and 2D Zinc-Based Metal-Organic Frameworks with Tetrazole Ligands.

We report the synthesis and structural diversity of Zn(II) metal-organic framework (MOF) with in situ formation of tetrazole ligand 3-ptz [3-ptz = 5-(3-pyridyl)tetrazolate] as a function pH. By varying the initial reaction pH, we obtain high-quality crystals of the noncentrosymmetric three-dimensional MOF Zn(3-ptz)2, mixed phases involving the zinc-aqua complex [Zn(H2O)4(3-ptz)2]·4H2O, and two-dimensional MOF crystals Zn(OH)(3-ptz) with a tunable microrod morphology, keeping reaction time, temperature, and metal–ligand molar ratio constant. Structures are characterized by X-ray diffraction, scanning electron microscopy, Fourier transform infrared spectroscopy, and UV–vis spectroscopy. We discuss the observed structural diversity in terms of the relative abundance of hydroxo-zinc species in solution for different values of pH.

Electrodegradation of tetracycline using stainless steel net electrodes: Screening of main effective parameters and interactions by means of a two-level factorial design

Performance of electrodegradation process using stainless steel net electrodes was explored for removal of tetracycline (TC) from synthetic wastewater in a laboratory batch study. Main effects of various operating parameters, such as initial TC concentration (20 and 100 mg/L), reaction pH (3.0 and 9.0), current density (4.1 and 17.1 mA/cm2), agitation speed (250 and 750 rpm), and electrolysis time (20, 50, and 80 min), and their interactions on the TC removal efficiency, were optimized by means of a five-factor and two-level factorial experimental design methodology. The significance of responses obtained from the proposed design (sixteen experimental runs under batch mode conditions) was statistically evaluated by preparing a Pareto chart, half-normal probability plot, and plots of main effects and their interactions (herein referred to as Factions) within the framework of the analysis of variance (ANOVA). The statistical results corroborated with 95% certainty that TC concentration, pH, and current density showed the largest effects (absolute values) on the TC removal efficiency. Besides the most effective Factions, a sodium sulfate (used as supporting electrolyte) dose of 1 g/200 cc was determined as the optimum value for the studied process. Under the conditions of an initial TC concentration=20 mg/L, a reaction pH=3.0, current density=17.1 mA/cm2, an agitation speed=250 rpm, and an electrolysis time=20 min, about 70% of TC could be successfully removed from the simulated wastewater. Findings of this experimental study clearly confirmed the applicability of the electrodegradation process for the removal of a broad spectrum antibacterial agent like TC, and also demonstrated the effectiveness of the factorial design methodology before transferring the obtained experimental knowledge for a full-scale facility.