Initial pH Conditions Research Articles

Investigation of kinetic, isotherm and adsorption efficacy of thorium by orange peel immobilized on calcium alginate

In this research work the thorium uptake on immobilized protonated orange peel was studied in a batch system. The effects of effective parameters such as biosorbent dosage, initial metal ion concentration, and contact time on the biosorption of thorium were analyzed. The biosorption capacity of the immobilized orange peel for thorium at optimal conditions of initial pH 3.8, biosorbent dosage 8 g/L, and initial thorium concentration 170 mg/L was found to be 18.65 mg/g. According to the results of contact time, the biosorption process reached equilibrium after around 10 h of contact. Investigation of the kinetics showed that the biosorption of thorium onto immobilized orange peel follows the pseudo-second-order model. The Langmuir and Freundlich isotherms were used to model the experimental equilibrium data. The results showed better agreement by the Langmuir isotherm. The maximum absorption capacity of immobilized protonated orange peel for thorium adsorption was predicted by the Langmuir isotherm at 29.58 mg/g.

Efficient removal of recalcitrant naphthenic acids with electro-cocatalytic activation of peroxymonosulfate by Fe(III)-nitrilotriacetic acid complex under neutral initial pH condition

This work investigated the activation of peroxymonosulfate by electrochemical (EC) system assisted with Fe(III)-nitrilotriacetic acid (NTA) complex for degradation of persistent naphthenic acids (NAs) under neutral initial pH conditions. As NAs are a complicated mixture, 1-adamantanecarboxylic acid (ACA) was selected as the model NA compound for degradation experiment. The addition of NTA is to chelate with Fe(III), gaining stability under neutral pH condition to facilitate the circulation of Fe(II)/Fe(III) by the electrochemical process to activate PMS. The EC/Fe(III)-NTA/PMS system was explored with applicable pH range of 3–9 and an optimized molar ratio 1: 2 for Fe: NTA. Results of quenching and chemical probe experiment together with results of electron paramagnetic resonance (EPR) analysis revealed the main reactive species of the system, including •OH, SO4•−, 1O2 and possibly Fe(IV). With the addition of NTA, the yields of •OH, SO4•−, 1O2 were enhanced. Results of mass spectrometry analysis and DFT calculations indicated the formation of 9 degradation byproducts of ACA via three primary degradation pathways such as hydroxyl substitution, carbonyl substitution, and decarboxylation. Furthermore, the EC/Fe(III)-NTA/PMS system could achieve excellent removal efficiency of ACA with different anions such as Cl-, HCO3-, NO3- and H2PO4- in the background. The practical applicability of the system was also verified with the high removal of commercial NAs mixture standard. Overall results have indicated the EC/Fe(III)-NTA/PMS system could be utilized for efficient reclamation of authentic oil and gas industrial wastewater under natural pH conditions.

Antimicrobial study and biosorption of Pb2+ ions onto chitosan-walnut composites: mechanistic studies and neuro-fuzzy modeling approach

The upsurge in the discharge of lead ions (Pb2+) into the environs resulting from various anthropogenic activities vis-vis its adverse effect on public health is a call for great concern. However, the adsorption technique, amongst other heavy metal removal methods, is regarded as the most promising. The present study synthesized a walnut shell-chitosan composite (WNS-CH) as an efficient biosorbent for Pb2+ uptake and biofilter of Bacillus subtilis and Klebsiella pneumoniae. WNS-CH was characterized using SEM and FTIR. Furthermore, an intelligent and cost-effective machine learning model, an adaptive neuro-fuzzy model clustered with the grid-partitioning (GP), and fuzzy c-means (FCM) technique were developed to predict the adsorption of Pb2+ based on relevant input parameters. The batch adsorption was carried out by varying operating parameters such as contact time, temperature, pH, adsorbent dose, and initial adsorbate concentration. The SEM images of WNS-CH showed a homogenous regular hollow ellipsoidal morphologies, while FTIR spectra showed the presence of O-H, N-H, C-N, and C-O. Under the conditions of initial pH 10, dosage 45 mg, and temperature of 40 °C, an adsorption efficiency of 94 % was obtained. The thermodynamic parameters, ∆H° and ∆G°, showed an endothermic and spontaneous process for Pb2+ uptake. Antibacterial activities of the WNS-CH composite showed bioactivity against Bacillus subtilis and Klebsiella pneumoniae with a mean ZI of 5.3±1.16 and 6.0 ±1.00, respectively. The experimental data was best described by Freundlich isotherm (R2= 0.9509) and pseudo-first-order kinetic (R2= 0.9674) models indicating chemisorption and multilayer adsorption process. The best prediction of Pb2+ adsorption was obtained with the optimal GP-clustered ANFIS model using a triangular membership function (triMF), giving Root Mean Square Error (RMSE), Mean Absolute Deviation (MAD), Mean Absolute Percentage Error (MAPE), and correlation determination (R1) values of 1.217, 0.563, 1.698, and 0.9966 respectively at the testing phase. The GP-ANFIS model shows good agreement with experimental results. This study revealed that WNS-CH composite could be regarded as a promising biosorbent for the remediation of Pb2+-polluted wastewater. The cost analysis demonstrated that the WNS-CH composite could serve as an alternative to commercial activated carbon.

Degradation of Sulfamethoxazole in Aqueous Solution by Low-Energy X-ray Irradiation

Antibiotic resistance has been a serious health threat of widespread concern, as antibiotics are difficult to degrade effectively in the environment. In this study, sulfamethoxazole (SMZ), a common antibiotic in an aqueous solution, was irradiated by low-energy X-ray to investigate the effect of the absorption dose, initial concentration, initial pH, irradiation energy and other conditions on the degradation of SMZ, as well as the kinetic mechanism of SMZ degradation. The results showed that low-energy X-ray irradiation could effectively degrade SMZ in an aqueous solution at different initial concentrations and acid-base degrees, and the degradation effect of irradiation in the range of 60–80 keV is independent of the energy of X-rays. The degradation rate of the SMZ solution, with an initial concentration of 10.70 mg/L, was 94.6% at an absorbed dose of 890 Gray, with a pH of 3.5. Similar to other works on the degradation of antibiotics by ionizing irradiation, the degradation of SMZ solutions conformed to a pseudo-first-order kinetic mechanism.

Enhanced reductive degradation of chloramphenicol by sulfidated microscale zero-valent iron: Sulfur-induced mechanism, competitive kinetics, and new transformation pathway

Crystalline iron sulfide (FeSx, i.e., FeS or FeS2) minerals as sulfur sources were used to prepare the mechanochemically sulfidated microscale zero-valent iron ((FeSx+ZVI)bm). Metastable FeS and FeS2 precursors were generated via aqueous coprecipitation and applied to fabricate FeSx@ZVI samples. (FeSx+ZVI)bm and FeSx@ZVI exhibited better chloramphenicol (CAP) degradation than ZVI due to the increase in specific surface areas, the decrease of electrochemical impedance, the formation of galvanic cells, and sulfur-induced pitting and local acidity. (FeSx+ZVI)bm had better CAP removal capacity than FeSx@ZVI under different S/Fe molar ratios, initial pH, and oxygen conditions. At the same time, FeSx@ZVI showed better electron utilization under oxic conditions, related to their Fe0 and sulfur spatial distribution. Nitro reduction and dechlorination of CAP by (FeSx+ZVI)bm produced nitroso, azoxy, amine, and monodechlorination products, while dechlorination was not involved in the degradation process of CAP by FeSx@ZVI. A new transformation pathway of nitroso-CAP to amine-CAP mediated by azoxy products is proposed via coupling a chain decay multispecies model and DFT calculations. The larger competitive reaction rates among O2, CAP, and its degradation products was determined by their lower LUMO energy. The contribution of direct electron transfer to nitro reduction was greater than that of atomic hydrogen, but the opposite was true for dechlorination. FeSx@ZVI had a larger DET contribution than (FeSx+ZVI)bm, and FeS2 promoted the DET contribution better than FeS. Toxicity assessment indicated that the rapid transformation of nitroso and azoxy products was crucial for eliminating the biotoxicity of CAP.

Hydrothermal Reactions of Biomass-Derived Platform Molecules: Mechanistic Insights into 5-Hydroxymethylfurfural (5-HMF) Formation during Glucose and Fructose Decomposition

The study investigates the primary reaction mechanisms of hydrothermal decomposition of glucose and fructose at 150–225 °C under various initial pH conditions (i.e., with an initial pH of 3–7) to reveal the formation mechanism of 5-hydroxymethylfurfural (5-HMF) from glucose and fructose. The results clearly show that dehydration to produce 5-HMF is not a primary reaction during hydrothermal decomposition of both glucose and fructose under noncatalytic conditions, indicating that 5-HMF cannot be directly produced from either glucose or fructose in water (with an initial pH of ∼7). In the presence of formic acid, dehydration to produce 5-HMF becomes a primary reaction during the hydrothermal decomposition of both glucose and fructose. The selectivity of dehydration reaction to produce 5-HMF increases with reducing the initial pH, i.e., up to ∼40% for glucose decomposition at 175 °C and ∼49% for fructose decomposition at 150 °C when the initial pH reduces to 3. Further kinetic analyses show that the rate constants of isomerization and retro-aldol condensation reactions almost remain unchanged under all initial pH conditions, while the rate constants of dehydration reactions to produce 5-HMF and levoglucosan increase almost linearly with the hydrogen ion concentration at the reaction temperature. This leads to increases in the selectivities of dehydration reactions, at the expense of other primary reactions. Our data also clearly indicate that dehydration reactions are acid-catalyzed reactions, while organic acid has almost no effect on isomerization and retro-aldol condensation reactions. Since organic acids can be formed at the early stage of sugar decomposition, this study provides the first experimental evidence in the field to clarify the formation mechanism of 5-HMF during sugar hydrothermal decomposition.

Walnut shells as a potential biosorbent for Cu(II), Pb(II) and As(III)/(V) ions removal from river waters

In this study, the potential of the walnut shell as a biosorbent for biosorption of Cu(II), Pb(II), and As(III)/(V) ions from river water samples was investigated. The effects of various conditions of water samples such as the initial ion concentration, sample pH, and contact time at a constant temperature and biosorbent dosage, on biosorption of Cu(II), Pb(II), and As(III)/(V) were investigated. Walnut shells, as the material with a high potential for removal of investigated ions, have biosorption efficiency of up to 99.6%, under the applied experimental conditions. The best adsorption time was obtained at 4 h for Cu(II), Pb(II), and As(III)/(V) ions. The maximum removal of 97.6% (Cu(II)), 82.9% (Pb(II)), and 99.6% (As(III)/(V)) was obtained at pH=4.43, pH=8.55, and pH=7.84, respectively. Hence, the walnut shell shows potential of a cost-effective biosorbent that could be used for the treatment of contaminated rivers. However, further investigation is needed to fully explore this potential.

Kinetics of the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation

In this study, high-gravity intensified heterogeneous catalytic ozonation is utilized for treatment of phenol-containing wastewater, and the kinetics of the direct reaction between ozone and phenol in the presence of excess tertiary butanol (TBA) is investigated. It is revealed that the direct reaction between ozone and phenol in the rotating packed bed (RPB) follows the pseudo-first-order kinetics with a reaction rate constant higher than that in the conventional bubbling reactor (BR). Under different conditions of temperature, initial pH, high-gravity factor, and gaseous ozone concentration, the apparent reaction rate constant varies in the range of 0.0160−0.115 min-1. An empirical power-exponential model is established to characterize the effects of these parameters on the direct reaction between ozone and phenol by high-gravity intensified heterogeneous catalytic ozonation.

Efficient Removal of Ciprofloxacin from Contaminated Water via Polystyrene Anion Exchange Resin with Nanoconfined Zero-Valent Iron.

Ciprofloxacin (CIP), an important emerging contaminant, has been frequently detected in water, and its efficient removal has become an issue of great concern. In this study, a nanocomposite material nZVI/PA was synthesized by impregnating nanoscale zero-valent iron (nZVI) inside a millimeter-sized porous host (polystyrene-based anion exchange resin (PA)) for CIP removal. The nZVI/PA composite was characterized by field emission scanning electron microscopy coupled with energy-dispersive X-ray, transmission electron microscopy, X-ray diffraction, as well as X-ray photoelectron spectroscopy, and it was confirmed that nZVI was uniformly dispersed in PA with a small particle size. Furthermore, several key factors were investigated including initial solution pH, initial CIP concentration, co-existing ions, organic ligands, and dissolved oxygen. The experimental results indicated that the nZVI/PA composites exhibited a high removal efficiency for CIP under the conditions of initial pH 5.0, and initial CIP concentration 50 mg L-1 at 25 °C, with the maximum removal rate of CIP reaching 98.5%. Moreover, the nZVI/PA composites exhibited high efficiency even after five cycles. Furthermore, quenching tests and electron spin resonance (ESR) confirmed that CIP degradation was attributed to hydroxyl (·OH) and superoxide radicals (⋅O2-). Finally, the main degradation products of CIP were analyzed, and degradation pathways including the hydroxylation of the quinolone ring, the cleavage of the piperazine ring, and defluorination were proposed. These results are valuable for evaluating the practical application of nZVI/PA composites for the removal of CIP and other fluoroquinolone antibiotics.

Leaching Mechanism and Health Risk Assessment of As and Sb in Tailings of Typical Antimony Mines: A Case Study in Yunnan and Guizhou Province, Southwest China.

The weathering and leaching of mining tailings have released large amounts of antimony (Sb) and arsenic (As), causing serious pollution in the surrounding soil, water, and sediments. To understand the leaching characteristics of Sb and As in mining tailings, Zuoxiguo and Qinglong mining tailings were collected for analysis. The average content of Sb in Zuoxiguo and Qinglong tailings was 5902.77 mg/kg and 1426.43 mg/kg, respectively, while that of As was 412.53 mg/kg and 405.26 mg/kg, respectively, which exceeded the local background value. Furthermore, the concentrations of Sb in the leachate of Zuoxiguo and Qinglong increased with time; the average Sb concentration in the leachate of Zuoxiguo and Qinglong was 1470.48 μg/L and 70.20 μg/L, respectively, while that of the As concentration was 31.20 μg/L and 6.45 μg/L, respectively. This suggests that the concentrations of Sb and As in the leachate of Zuoxiguo are both higher than those in the leachate of Qinglong and that the pH of the leachate of Zuoxiguo and Qinglong significantly changed within the first day under different initial pH conditions, and tended to be between 6 and 8, after one day. The results of the average health risk index showed that As in the leachate from Zuoxiguo and Qinglong for children was 5.67 × 10-4 and 9.13 × 10-5, respectively, and 4.43 × 10-4 and 7.16 × 10-5, respectively, for adults. As in the leachate from Zuoxiguo poses serious carcinogenic risks for residents, and in the study area, As poses a serious threat to human health. Therefore, the local government must manage As in these areas.

Comparative Study of Methane Production in a One-Stage vs. Two-Stage Anaerobic Digestion Process from Raw Tomato Plant Waste

An anaerobic digestion process performed in two stages has the advantages of the production of hydrogen in addition to methane, and of further degradation of the substrate over the conventional process. The effectiveness of the implementation of this system for the treatment of lignocellulosic waste has been demonstrated. In 2020, more than 180 million tons of organic waste were generated worldwide from tomato crop production, posing a serious environmental risk. In the present investigation, methane production was compared in a two-stage system versus one-stage system from non-pretreated tomato plant residues. For this, different temperature (37 and 55 °C) and initial pH (5.5 and 6.5) conditions were evaluated during hydrogenesis and a constant temperature (37 °C, without pH adjustment) during methanogenesis. At the same time, a one-stage treatment (37 °C, without pH adjustment) was run for comparison purposes. The two-stage treatment in which the highest production of hydrogen, 12.4 mL/g VS, and methane, 252.3 mL/g VS, was observed occurred under the conditions of pH 6.5 and at 37 °C. However, this energy production was statistically similar (p < 0.5) to the one-stage treatment (365.4 mL CH4/g VS). Furthermore, there were also no significant differences in the removal of volatile solids between the different treatments.

Tannin-diethylenetriamine based adsorbents with exceptional adsorption capacity of Chromium(VI) in aqueous solution

Background: In order to remedy the pollution of chromium(VI), it is of great significance to develop high-efficiency adsorbents.Methods: Heren, excellent adsorbents poly(polyethyleneimine-tannin-diethylenetriamine) (PPTD) were synthesized using a simple route and utilized for the removal of Cr (VI) from aqueous solutions. The effect of various factors on the adsorption behavior of PPTD was studied, such as polyethyleneimine content, temperature, initial pH, initial concentration, adsorbent dosage, contact time, and foreign ions. The optimized experiments were performed under the conditions of polyethyleneimine content (35%), temperature (30 °C), initial pH (2), initial concentration (200 mg L−1), and contact time (24 h) using 25 mg PPTD to remove Cr(VI) for 100 mL solution.Significant Findings: The results not only showed rapid removal efficiency which is close to 100% at low concentrations (20∼120 mg L−1), but also exhibited favorable selectivity for Cr (VI) even in the presence of coexisting ions (such as Cl−, Cd (II), and Cu (II)). Its maximum capacity reached the value of 757.6 mg g−1 at 30 °C, which was close to the experiment data (751.6 mg g−1). Besides, the adsorption behavior of Cr (VI) can be described by the pseudo-second-order kinetic model and the Langmuir isothermal model. Following satisfactory fitting with the Langmuir isotherm model.

Bioleaching of tellurium from mine tailings by indigenous Acidithiobacillus ferrooxidans.

Tellurium (Te) is a scarce and valuable metalloid, which can be found in some mine tailings. In this work, an indigenous Acidithiobacillus ferrooxidans strain was used to leach Te from mine tailings collected in the Shimian Te mine region, China. Under the optimized conditions of initial pH of 2·0, pulp density of 4% and temperature of 30°C, 47·77% of Te can be dissolved after 24 days of bioleaching. The leaching of Te by different systems such as bioleaching, Ferric ion (Fe(III)) leaching and acid leaching was compared. The results showed that the leaching behaviour of Te is similar to that of sulphur in sulphide minerals, that is, Fe(III) first oxidizes telluride (Te(-II)) in minerals to elemental Te, and then elemental Te can be oxidized by bacteria to Te(IV) and Te(VI). Besides, it was also showed by scanning electron microscope observation and Fourier transform infrared spectroscopy analysis of the ore sample before and after bioleaching that some bedded structure covered on the surface of the ore after bioleaching acting as a reaction compartment, and the changing of active groups indicated a possible attachment between bacteria and ore. There is an indirect mechanism involved in bioleaching of Te.

Initial pH Conditions Shape the Microbial Community Structure of Sewage Sludge in Batch Fermentations for the Improvement of Volatile Fatty Acid Production.

Conversion of wastewater treatment plants into biorefineries is a sustainable alternative for obtaining valuable compounds, thus reducing pollutants and costs and protecting the environment and human health. Under specific operating conditions, microbial fermentative products of sewage sludge are volatile fatty acids (VFA) that can be precursors of polyhydroxyalkanoate thermoplastic polyesters. The role of various operating parameters in VFA production has yet to be elucidated. This study aimed to correlate the levels of VFA yields with prokaryotic microbiota structures of sewage sludge in two sets of batch fermentations with an initial pH of 8 and 10. The sewage sludge used to inoculate the batch fermentations was collected from a Sicilian WWTP located in Marineo (Italy) as a case study. Gas chromatography analysis revealed that initial pH 10 stimulated chemical oxygen demands (sCOD) and VFA yields (2020 mg COD/L) in comparison with initial pH 8. Characterization of the sewage sludge prokaryotic community structures—analyzed by next-generation sequencing of 16S rRNA gene amplicons—demonstrated that the improved yield of VFA paralleled the increased abundance of fermenting bacteria belonging to Proteobacteria, Bacteroidetes, Chloroflexi, and Firmicutes phyla and, conversely, the reduced abundance of VFA-degrading strains, such as archaeal methanogens.

Efficient degradation of bisphenol A by the UV-enhanced nano zero-valent iron-activated hydrogen peroxide advanced oxidation system

Bisphenol A (BPA) in a water environment has hazardous and is difficult to degrade under natural conditions. In this study, the UV-nZVI-H2O2 system was constructed to efficiently degrade BPA. The results show that the removal rate and mineralization rate of BPA were 85.03 % and 21.31 %, respectively, under the conditions of initial pH = 3, UV = 10 W, [nZVI] = 0.05 g/L, [H2O2] = 0.06 mmol/L, [BPA] = 40 mg/L and t = 60 min. This is mainly attributed to the synergistic effect among UV, nZVI and H2O2. The dominant reactive oxygen species in the UV-nZVI-H2O2 system was HO•, and the yield of HO• was up to 333.81 μmol/L, which was much higher than that of other systems in the controlled experiment. In addition, the system can efficiently remove a variety of aromatic and refractory organic matter (e.g., ibuprofen (IBU) and ciprofloxacin (CIP)). The reaction intermediates were identified, and it was speculated that the possible degradation pathways of BPA were mainly HO• attack on the electron-rich benzene ring in the BPA molecule and attack on the C–C bond connected between isopropyl and the benzene ring. The possible degradation pathways of IBU include decarboxylation, hydroxylation addition and single bond breaking. The possible degradation pathway of CIP is the loop opening of the piperazine ring and quinolone ring of CIP after continuous oxidation of HO•. The reaction mechanism of this system is a homogeneous and heterogeneous Fenton reaction and adsorption and precipitation of BPA by iron-based oxides.

Denitrification of nitrate in regeneration waste brine using hybrid cation exchanger supported nanoscale zero-valent iron with/without palladium nanoparticles

The Sustainable Development Goals require that reducing waste is a priority. This work described the application of an innovative zero-waste hybrid ion exchange nanotechnology that concurrently removed nitrate and induced denitrification to ammonia, with the ability to generate fertilizer for the agriculture sector from the recycled by-products. Herein, hybrid cation exchanger-supported zero-valent iron (Fe0), and bimetallic Fe0/Pd nanoparticles (HCIX-Fe0 and HCIX-Fe0/Pd) were synthesized and successfully validated for denitrification of nitrate in spent waste brine that contained nitrate. The kinetics of nitrate catalysis by both HCIX-Fe0 and HCIX-Fe0/Pd were compared and presented by six kinetic models, namely, zero-order, pseudo first- and second-order reaction, pseudo first- and second-order adsorption, and Elovich. HCIX-Fe0/Pd displayed a higher kinetic value than HCIX-Fe0, with k1 of 0.0019 and 0.0026 min−1, respectively. Nitrate was predominantly catalysed to NH4+ at a ratio of ammonia to other nitrogen compounds of around 80:20. Although HCIX-Fe0/Pd showed slightly better (14%) kinetic results, it was determined as unfavourable for real-life application due to low selectivity toward N2 gas and the need to use H2 gas. Based on practicability, the HCIX-Fe0 was further validated. The effect of salt (using NaCl) and the role of initial pH conditions were optimized and discussed. The recovery of nitrate removal was also calculated, and a recovery range of 91.42–99.14% was obtained for three consecutive runs. The sustainable, novel, zero waste hybrid ion exchange nanotechnology using the combination of two fixed-bed columns containing nitrate-selective resin for nitrate removal and novel HCIX-Fe0 for nitrate reduction to NH4+ may be a promising sustainable solution toward the goal of discharging zero nitrate waste to the environment.

Simultaneous removal of lead, chromium and cadmium from synthetic water by electrocoagulation: Optimization through response surface methodology

Present research was conducted to remove lead, chromium and cadmium simultaneously from synthetic water by electrocoagulation (EC) process using iron electrodes. Process parameters such as initial pH, current density, and treatment time were optimized using Box- Behnken design (BBD) of Response Surface Methodology (RSM). A high R2 value of Analysis of variance ensuring a satisfactory adjustment of the second-order regression model with the experimental data. Under the optimum conditions of initial pH: 5, current density: 140 A/m2, treatment time: 40 min the removal of lead, chromium, and cadmium were obtained as 99.9 %, 94.3 %, and 99.9 %, respectively. Results confirmed the validity of the EC process optimization and the adequacy of the model. Furthermore, the lead and cadmium concentration in treated water is also found below the level set by the CPCB for Indian effluent discharge.

Pengaruh Variasi Media Pertumbuhan terhadap Aktivitas Peredaman Radikal Bebas DPPH Ekstrak Kapang Endofit Isolat Cb.D1

Endophytic fungi are a source of antioxidant compounds in nature. The low yield of extracts and active compounds produced is one of the limiting factors for using endophytic fungi as a source of natural antioxidant compounds. Modification of growth media is an alternative solution to overcome this problem. This study aimed to determine the effect of media conditions, belonging to carbon and nitrogen sources and different initial pH of fermentation, on the antioxidant through DPPH radical scavenging activity of extract of endophytic fungi Cb.D1 isolated from cinnamon plant leaves. The culture was propagated using Czapek Dox Broth basal liquid medium with agitation speed 120 rpm at room temperature for 14 days. The carbon sources used were glucose, sucrose, and soluble starch. The nitrogen sources were natrium nitrate, ammonium nitrate, and yeast extract. The initial pH conditions used were 5, 7, and 9, and ethyl acetate as the extraction solvent. The results obtained that the variation of nitrogen and carbon sources and also initial pH conditions can increase the yield of extract of endophytic fungi Cb.D1. Glucose, yeast extract, and initial pH at 9 were the best growth media to gain it. The substitution of nitrogen sources and initial pH can increase the DPPH free radical scavenging activity of endophytic fungal extract compared to substitution for carbon sources. The highest activity from the Cb.D1 endophytic fungal extract was obtained from media that contain sucrose and natrium nitrate as a carbon and nitrogen sources and an initial pH of 5. The Variation of growth media of endophytic fungi Cb.D1 affected their extract in DPPH free radical scavenging activity.

ZnO-Zn2TiO4 heterostructure for highly efficient photocatalytic degradation of pharmaceuticals.

In this study, ZnO-Zn2TiO4 (ZTM) material was prepared through a novel synthesis method based on a ultrasound-assisted polyol-mediated process followed by calcination at a different temperature. Physical features of the samples were studied by using various analysis techniques including XRD, FT-IR, SEM/EDX, pHPZC, and UV-Vis DRS. Subsequently, the materials were employed as catalysts for the photocatalytic degradation of clofibric acid as a model pharmaceutical contaminant. The photocatalytic performance was evaluated under different conditions of calcination temperature, catalyst dosage, starting concentration, and initial pH of clofibric acid solution. The finding results revealed that hexagonal-tetragonal phases of ZnO-Zn2TiO4 calcined at 600°C (ZTM-600) with an average crystallite size of 97.8Å exhibited the best degradation efficiency (99%). The primary bands characteristic of ZnO and Zn2TiO4 were displayed by FT-IR analysis and the UV-visible DRS confirms the larger absorption capacity in UV-visible regions. The photogenerated electrons are the powerful reactive species involved in clofibric acid photodegradation process. This study shows a promising photocatalyst and provides new sight to rational design the facets of photocatalysis process for enhanced photocatalytic performances and effective wastewater treatment.

Chitosan-Modified Biochar and Unmodified Biochar for Methyl Orange: Adsorption Characteristics and Mechanism Exploration.

In this study, shrimp shell-derived chitosan (CS) and rice husk-derived biochar (RHB) were produced; CS and RHB were then used to synthesize chitosan-modified biochar (CSBC) hydrogel beads. N2 adsorption (77K), SEM-EDX and FT-IR techniques were used to evaluate the physicochemical properties of the adsorbents. A batch experiment was conducted to test the methyl orange (MO) adsorption performance of RHB and CSBC. The results showed that the MO adsorption process was strongly pH-dependent. The kinetics were well described by the pseudo-second-order and intra-particle diffusion models, assuming the chemisorption and intraparticle diffusion mechanisms govern the adsorption process. Homogeneous adsorption for MO on the surface of RHB and CSBC was also assumed since the isotherm data showed the best-fit to the Langmuir model. Under the experimental conditions of initial pH 3, dosage 0.2 g, contact time 240 min and temperature 298 K, the maximum adsorption capacity of CSBC and RHB for MO dye adsorption was 38.75 mg.g−1 and 31.63 mg.g−1, respectively. This result demonstrated that biochar had better performance after modification with chitosan, which provided more functional groups (i.e., −NH2 and −OH groups) for enhanced electrostatic interactions and complexation between MO and CSBC. Overall, CSBC is an effective adsorbent for the removal of MO from aqueous solution.