Al2O3/Fe3O4/ZrO2 ternary oxide sorbent: Synthesis, characterization and sorption behavior to fluoride and phosphate ions from aqueous solution

ABSTRACT. Excess quantities of fluoride and phosphate in water bodies can lead to fluorosis and eutrophication problems, respectively. In search of a promising adsorbent targeting these ions, Fe3O4/Al2O3/ZrO2 ternary oxide was synthesized via co-precipitation method and characterized by X-ray diffraction (XRD), Fourier transform-infrared (FTIR) and Brunauer-Emmer-Teller (BET). Its specific surface area was found to be 205 m2/g. The effects of solution pH, adsorbent dose, contact time, agitation speed and initial fluoride and phosphate concentrations were also investigated and the optimum values were 4, 0.5 g, 12 h, 100 rpm and 20 mg/L, respectively, for fluoride and 5, 0.1 g, 8 h, 100 rpm and 10 mg/L, respectively, for phosphate. Fluoride and phosphate adsorptions fitted well with Freundlich and Langmuir isotherm models, respectively and their kinetic data correlated well with the pseudo-second order model. Desorbability study revealed that maximum desorption was achieved at pH 12. Thermodynamics study on the other hand showed that adsorption of fluoride was nonspontaneous and endothermic whereas that of phosphate was spontaneous and exothermic. Application on real water sample decreased the concentration of fluoride from 4.92 to 1.97 mg/L in ground water and phosphate from 1.7 to 0.35 mg/L lake water showing its potential as a promising adsorbent.   KEY WORDS: Adsorption, Fluoride, Phosphate, Ternary oxide sorbent, Isotherm models   Bull. Chem. Soc. Ethiop. 2022, 36(3), 555-569.                                                               DOI: https://dx.doi.org/10.4314/bcse.v36i3.6                                                         &nbsp

Preparation and sorption property study of Fe3O4/Al2O3/ZrO2 composite for the removal of cadmium, lead and chromium ions from aqueous solutions

Fe-Al-Zr ternary mixed oxides composite was synthesized via co-precipitation method for the removal Pb(II), Cd(II) and Cr(VI) ions from aqueous solutions. The as-synthesized materials were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), scanning electron microscope hyphenated with energy dispersive X-ray diffraction (SEM-EDX) and Fourier transform infrared (FTIR) techniques. The pH at the point of zero charge (pHpzc) of the sorbent and effect of ionic strength on sorption were also determined. The batch tests were conducted to optimize the various sorption parameters such as pH, adsorbent dose, contact time, speed of agitation and initial metal concentration. The experimental results showed that the adsorbed amounts of Pb(II), Cd(II) and Cr(VI) tend to decrease with increase in pH. Freundlich isotherm model fits better the equilibrium data for the adsorbent. Kinetic data correlated better with both pseudo first order and pseudo second order kinetic models. The spontaneous nature of the adsorption process was also confirmed from thermodynamic grounds. The nanosized adsorbent exhibited an adsorption efficiency of 96.65%, 96.55% and 97.2% for Cd(II), Cr(VI) and Pb(II), respectively, at optimum condition. Experimental results showed that the nanocomposite was effective for the removal of the title heavy metals from aqueous solution.   Bull. Chem. Soc. Ethiop. 2020, 34(1), 105-121. DOI: https://dx.doi.org/10.4314/bcse.v34i1.1

Polyaniline-tin(IV) molybdophosphate composite exchanger: Photocatalytic behavior and antibacterial activitiy

ABSTRACT. Polyaniline-tin(IV)molybdophosphate composite exchanger was prepared using sol–gel method by mixing polyaniline gel into the inorganic precipitates of tin(IV)molybdophosphate. The composite ion exchanger was characterized by various techniques such as XRD, UV-Vis, FTIR, SEM-EDX, and PL. Photocatalytic activities and antibacterial efficiencies of the bare polymer polyaniline (PANI), the inorganic exchanger tin(IV)molybdophosphate (TMP) and the composite polyaniline-tin(IV)molybdophosphate (PANI-TMP) were evaluated using methylene blue (MB) dye as a model organic pollutant and Gram negative and Gram positive bacteria as test microbes, respectively. Photocatalytic and antibacterial activities of polyaniline[1]tin(IV)molybdophosphate composite was found to be higher than that of organic (polyaniline) and inorganic (tin(IV)molybdophosphate) counterparts. The results obtained indicated the degradation efficiency of approximately 73% in 180 min exposure time. Effect of scavengers study evidenced the most important species in the degradation process to be (·O2 - ) and (·OH). Highest photocatalytic degradation efficiency for the composite exchanger studied was obtained at initial concentration of 10 mg/L MB, 100 mg/L of catalyst load and a pH of 8. Antibacterial efficiency of the exchanger over both Gram negative and Gram positive bacteria was found to be higher than the single counterparts. KEY WORDS: Ion exchangers, Antimicrobial activity, Composites, Photocatalysis, Polyaniline Bull. Chem. Soc. Ethiop. 2023, 37(1), 59-76.                                                                  DOI: https://dx.doi.org/10.4314/bcse.v37i1.6                                                                                                      &nbsp

MWCNTs/Ag-ZnO nanocomposite for efficient photocatalytic degradation of congo red

Three nanomaterials namely, zinc oxide (ZC), silver-doped zinc oxide (AZ) and multi-walled carbon nanotubes coupled with silver doped zinc oxide nanocomposite (MWAZ) were synthesized, characterized and employed for photo degradation of an organic pollutant, congo red (CR). The photocatalytic activity study showed efficient degradation of CR upon irradiation with UV and visible light in the order of MWAZ > AZ > ZC > Commercial ZnO (ZCO). Percentage photodegradation of 99% and a pseudo 1st order rate constant of 2.3 x 10-2 min-1 were achieved by MWAZ as a catalyst under visible light irradiation, implying photo- sensitizing ability of MWCNTs and the capability of MWCNTs to hinder recombination of photogenerated holes and electrons. The control experiment in the dark condition gave only 7.9% of degradation efficiency and 5.56 x 10-4 min-1 rate constant, implying the significant role of light source for catalytic degradation of CR.   Bull. Chem. Soc. Ethiop. 2020, 34(1), 55-66. DOI: https://dx.doi.org/10.4314/bcse.v34i1.

Fe–Al binary oxide nanosorbent: Synthesis, characterization and phosphate sorption property

Phosphorous removal using efficient treatment approach such as adsorption is vital for the control of eutrophication. In this study, nanosized Fe-Al binary oxide sorbent was synthesized through a modified gel evaporation method and employed for adsorption of phosphate from aqueous system. The nanosorbent was characterized by x-ray diffraction (XRD), scanning electron microscope coupled with energy dispersive x-ray spectroscopy (SEM/EDX), tunneling electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and flame atomic absorption spectroscopy (FAAS). Langmuir model showed the best fit to the experimental data with a maximum adsorption efficiency of 16.4 mg/g. Having all parameters optimized, it has been found that the nanosorbent exhibited 99.86% phosphate adsorption efficiency. The effect of co-existing anions on the adsorption of phosphate was also studied and no significant effect on the efficiency of the nanosorbent was observed due to competing ions such as fluoride. Desorbabilty of phosphate was investigated and found to be increased with increasing pH. The results of thermodynamic studies indicated that the process is spontaneous and endothermic. Both macroscopic and microscopic approaches were employed to predict the mechanism of phosphate adsorption on the Fe-Al binary oxide nanosorbent. Accordingly, the phosphate adsorption is presumed to occur via the replacement of surface hydroxyl groups by the phosphate species and formation of inner-sphere surface complexes at the water/oxide interfac

Sustainable synthesis of semicrystalline Zr-BDC MOF and heterostructural Ag3PO4/Zr-BDC/g-C3N4 composite for photocatalytic dye degradation

[EN] Zr-based MOFs have stimulated the interest of scientific community due to their exceptional variety in composition, structure and chemical environment as well as their consequent applications including photocatalysis. This work presents the successful preparation of nanosized highly-porous Zr-BDC MOFs under sustainable conditions: at room temperature, water as sole solvent, and with no modulators. This approach solves some environmentally unfriendly drawbacks and feasible requirements of the conventional UiO-66(Zr), whereas both materials contain practically equal linker conformation and clusters structure and linker-cluster coordination. Furthermore, ternary composites of Zr-MOF combined with g-CN and AgPO are described for the first time. X-ray Photoelectron Spectroscopy (XPS), and Scanning and Transmission Electron Microscopies (SEM and TEM) evidenced ample and efficient interaction between the components within the composites. Such composites were tested as photocatalysts in the discoloration of methylene blue (MB), reaching degradation as high as 95% and 93% within 240 and 105 min under indoor/visible and outdoor/solar irradiations, respectively, far exceeding the photoactivity given by the individual components and by any of the two possible binary composites. These results suggest the existence of relevant synergistic effects in the heterostructures, which favors efficient interfacial charge transfer and improves the separation of photoinduced electron-hole pairs. The photoinduced hole (h) has more quenching effect than hydroxyl (.OH) and supper oxide (.O) radicals. In addition, the as-obtained ternary composite exhibited remarkable stability and recyclability, at least for the two cycles considered in the present work. We have also proposed a plausible reaction mechanism for the photocatalytic process.Spanish Research Council CSIC (i-COOP+2018) COOPA20271 project number, for funding. This research work was also financially supported by Haramaya University (HURG-2020–03-02–75, Ethiopia) and Debre Berhan University. They also thank financial support by the Agencia Estatal de Investigación (PID2019–107968RB-I00/AEI/10.13039/501100011033, Spain

Chemical forms of phosphorous and physicochemical properties of acid soils of Cheha and Dinsho districts, southern highlands of Ethiopia

Abstract Background Soil acidity and low availability of P are among the major problems limiting crop production in the highlands of Ethiopia. The current study was conducted to evaluate the distribution of chemical P forms and selected physical and chemical properties of soils in Cheha and Dinsho districts, southern highlands of Ethiopia. Twelve representative composite soil samples were collected from the surface layer (0–15 cm) and analyzed for selected soil properties. Analysis of available P and oxalate extractable P, Al and Fe, and P fractionation were done following standard procedures. Results The pH of soils in the study area ranged from 4.65 to 5.45. In the study area the Mehlich-3 extractable P ranged from 8.90 to 25.75 mg kg−1, while the Bray-I extractable P varied from 8.54 to 22.81 mg kg−1. The studied soils had a total P content that ranged from medium to very high. Mehlich-3 P was positively and significantly correlated with pH, CEC and OM, while it was negatively and significantly (P ≤ 0.01) correlated with exAc and exAl. Oxyhydroxides of iron and aluminum were dominating the exchange sites of the studied soils. In terms of the relative abundance of P forms, Res-P and HCl-P followed by NaOH-Po and NaOH-Pi were the dominant P forms in Cheha and Dinsho districts respectively. The total sum of readily available P forms (NH4Cl-Pi, NaHCO3-Pi and NaHCO3-Po) did not exceed 4% of the total P. Conclusion Soils of the study area were acidic in reaction and found to have low available P. Given the presence of considerable amount of total P, low P availability and high soil acidity in the study areas, further research has to be done on adsorption characteristics to determine the P requirements of the soils for better P management

Kinetics of phosphorus desorption from soils using a modified DMT-HFAO technique and its relationship with phosphorus fractions and maize (Zea mays L.) yield

This research investigated the kinetics of phosphorus (P) release from soils by employing an improved technique-hydrous ferric aluminium binary oxide in dialysis membrane tubes (DMT-HFAO). The as-synthesized adsorbents were characterized by x-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FTIR), thermogravimetic (TGA/DTA) and Brunauer-Emmett-Teller (BET) techniques. The modified method, DMT-HFAO, was used in six soils equilibrated for a period from 1 to 42 days. Two component first order model was applied to estimate the cumulative P desorbed and P desorption indices and how these parameters are related to maize yield. The cumulative P-extracted by DMT-HFAO over 42 days significantly correlated (p < 0.01) with maize plant uptake; better than the reference single system (DMT-HFO). This indicated that DMT-HFAO is superior in mimicking plant mode of action as compared to the benchmark, DMT-HFO. Among the P fractions, HCO3-Pi, HCO3-Po and D/HCl significantly correlated with the yield parameters in both techniques. Our findings, therefore, provide some insights on the importance of this modified technique in estimating the residual P in soil. Accurate estimation of residual P is important not only from environmental perspective but also from the judicious use of this non-renewable fertilizer

Effects of natural and modified zeolite based composite fertilizers on slow release and nutrient use efficiency

Excessive use of chemical fertilizers causes serious environmental hazards, as only a fraction is really adsorbed by the soil. As part of the solution, the feasibility of using unmodified (UNZC) and surfactant-modified natural zeolite-based composite (SMNZC) fertilizers as support materials for the provision of nutrients to soil on a slow release basis was assessed using column and pot experiments. The characterization of the zeolite materials was done using powder XRD, XRF, SEM, BET, and TGA instruments. The percentage of cationic nutrients released from soil columns containing UNZC increased over time. Their release from SMNZC initially slowed down and became stable as the number of days increased. The percentage of N–NO3− and available P released from UNZC has constantly decreased with time. Their release from SMNZC increased as the number of days increased. The maximum P uptake by maize was observed for the soil treated with SMNZC, and there was no significant difference at all rates. The maximum uptake of Ca (3663.40 ppm), Mg (2617.34 ppm), and Fe (222.83 ppm) was observed at 250 kg/ha of UNZC. The highest uptake of K, Zn, and Cu was also observed for the soil amended with UNZC, irrespective of its application rate. Application of UNZC and SMNZC at the same rate equally affected total nitrogen uptake. Thus, this finding showed that UZNC is a better carrier of cationic nutrients, while SMNZC is preferable for the slow release of NO3− and available P. In conclusion, both the modified and unmodified support forms showed better performance than conventional fertilizer in delivering nutrients slowly and sustainably

Synthesis, characterization and photocatalytic activity study of synthetic zeolite supported- ZnO-Fe2O3-MnO2 nanocomposite for methylene blue degradation

Trabajo presentado en el 30th Annual Congress of the Chemical Society of Ethiopia, celebrado en Mekelle (Etiopía) del 28 de febrero al 2 de marzo de 2014.ZnO-FeZ03-MnOZ nanocomposites were synthesized via one step impregnation of MnOz powder with an aqueous solution of Zn{lI) and Fe(lIl) nitrate salts. Zeolite supportedZnO-FezOrMnOz composite was prepared by solid state reaction. The morphology, structure and elemental analysis of as-synthesized nanocomposites were studied by using XRD, SEM/EDX, UV-visible and AAS spectrophotometry. Photocatalytic degradation activities of as-synthesized nanocomposites under visible light irradiation have been evaluated in the reduction of aqueous methylene blue (MB) dye solution and real sewage samples collected from Dire Dawa Textile Industry. Zeolite supported-ZnO-Fez03-MnOz photocatalyst exhibited effective degradation efficiency of methylene blue (MB) dye and real sewage sample to the extent of approximately 93% and 63%, respectively. The photocatalvtic efficiency of the naked ZnO-Fez03-MnOz nanocomposite was found to be 77% under visible light irradiation, significantly lower than the supported mixed oxide indicating that zeolite plays a role in the performance of the composite. When the visible light hit the VB of combined semiconductor, CB electrons can be ejected from the low band gap semiconductor (FeZ03) to the high band gap semiconductor (ZnO) and on the contrary, hole transfer can take place from the VB of high band gap semiconductors (ZnO) to the VB of small band gap semiconductor (FeZ03)' Additionally the presence of electron acceptor Mn(IV) could scavenge the excited electrons and altogether prevent the recombination of electron-hole pairs. While these constituents along with the zeolite framework, serve as an electron acceptor and delay the rate of photogene rated electron-hole pairs recombination as well as to increase the surface area that could give more active surface sites to absorb water molecules and to form active hydroxyl radical by trapping the photo-generated holes. Photocatalytic degradation of methylene blue dye (MB) follows pseudo first order kinetics for all as-synthesized nanocomposites.Peer Reviewe