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This study developed eco-friendly composite hydrogel based on cellulose and bentonite to remove Pb2+ from wastewater. The composite hydrogel adsorbents' morphology, chemical composition, and structure were characterized using FE-SEM, EDX, FT-IR, and XRD. Furthermore, EDX mapping displayed uniform dispersion of bentonite within the cellulose-based hydrogel (H), leading to enhanced swelling capacity and mechanical strength. To optimize the adsorption process, the effect of experimental conditions on the amount of Pb2+ adsorbed per bentonite/cellulose-based composite hydrogel (BCH3) was investigated. The batch adsorption results showed that the maximum adsorption capacity of Pb2+ onto BCH3 was 110.64 mg g-1. Post-adsorption EDX spectra and FTIR analysis provided evidence of successful Pb2+ uptake by BCH3. The results obtained from these analyses suggest that the primary adsorption mechanism involves the interaction of Pb2+ with nitrogen (NH2) and oxygen (COO-) groups on the BCH3 surface. Kinetics and isotherm data were best described by the pseudo-second-order (R2 = 0.999) and Sips models (R2 = 0.996). The kinetic model indicated that Pb2+ uptake onto the BCH3 was primarily governed by chemisorption involving coordination bonding/electrostatic interactions. The BCH3 adsorbent exhibited selectivity towards Pb2+ compared to Cd2+ and demonstrated good reusability after five adsorption-desorption cycles.

Abstract Chromium (VI) is known to be harmful element that commonly found industrial waste, mining activities, and wastewater discharges from various industries. When released into the environment, Cr (VI) can contaminate soil, water, and air, posing a serious threat to living organisms. Aiming to Cr decontamination, this work was framed to isolate the fungal species having high Cr tolerance capacity and to exploit as bio-sorbent for the removal of Cr (VI) from aqueous solutions by biosorption. Among the fungal species isolated from the Cr (VI) contaminated soil sample, the filamentous fungus of Ophiocordycipitaceae family, Purpureocillium lilacinum was identified using molecular sequencing technique, showed maximum tolerance against Cr (VI) with a tolerance index of 1.19 ± 0.23. Further, Plackett Burman Design was applied to investigate for ascertaining the significance of different carbon and nitrogen sources on P. lilacinus growth, as well as the influence of environmental factors, such as pH, temperature, and Cr (VI) concentration. The results explicated that glucose was the most preferred carbon source for P. lilacinus, while yeast extract was the most preferred for nitrogen source. The optimum pH value and temperature were found to be 6.0 and 26 °C, respectively. In addition, P. lilacinus isolate was identified to survive in high concentrations of Cr (VI), indicating its potential for employing effective bioremediation of chromium-contaminated site.

In this study, bentonite/amino-functionalized cellulose composite (BAC) adsorbent was synthesized by intercalating the hexadecyl trimethyl ammonium bromide surfactant (HDTMA) into bentonite followed by exfoliating the HDTMA-modified bentonite (MB) into amino-functionalized cellulose (AC). The physicochemical properties of BAC were evaluated by FTIR, XRD, FE-SEM, EDX, TGA, and Zeta potential measurement. A series of batch mode adsorption experiments were carried out to identify the optimal adsorption conditions as a function of experimental variables such as pH of solution, uptake time, initial Pb2+ concentrations, BAC dosage, and assess both percent removal (%) and Pb2+ uptake (mg g−1). The result demonstrated that the synergetic advantage of combining HDTMA-modified bentonite (MB) and amino-functionalized cellulose (AC) in Pb2+ uptake (69 mg g−1) surpassed that of HDTMA-modified bentonite (12.14 mg g−1) and amino-functionalized cellulose (31.33 mg g−1) alone. Further, Pb2+ uptake onto BAC was higher than the HDTMA-modified bentonite/cellulose composite (BC) (42.12 mg g−1) due to the introduction of the amino group to cellulose through grafting with ethylenediamine (EDA). The adsorption of Pb2+ from aqueous solution by BAC fit well with pseudo - 2nd-order kinetic (R2 = 0.998) and Langmuir isotherm (R2 = 0.999) models. The kinetic study indicated that the active sites in the BAC exhibit heterogeneity and possess different activation energies for chemisorption. The monolayer attachment of Pb2+ onto the BAC surface was realized from the isotherm study, and the maximum predicted adsorption capacity was found to be 71.869 mg g−1. Regeneration studies showed that BAC maintained its good Pb2+ uptake capacity for up to four cycles.

Water pollution, driven by Pb2+, poses a significant threat to biotics and the environment. A promising solution to address the issue is the utilization of cellulose from lignocellulosic materials as an adsorbent to remove or reduce Pb2+ from wastewater. However, as reported, the adsorption capacities of native cellulose adsorbents vary depending on their plant source, and their metal binding capacity is not as satisfactory as expected due to a lack of robust chelation sites, particularly amino groups. Thus, this study aimed to improve Pb2+ uptake capacity by utilizing the prosopis juliflora stem, a previously unexplored cellulose source, as an adsorbent through ethylenediamine (EDA) grafting. FTIR, XRD, FE-SEM, EDX, and TGA evaluated the physicochemical properties of amino-decorated cellulose (ADC) adsorbent. The effect of experimental variables (initial Pb2+ concentration, ADC dose, and contact time) on percent removal was investigated and analyzed using Box-Behnken Design (BBD). Analysis of variance (ANOVA) revealed that, among the interaction effects, only the interactions between initial Pb2+ concentration and ADC dose significantly affected percent removal (P

In this study, a KNO3-loaded coffee husk (CH) ash catalyst was synthesized to produce waste frying oil methyl ester (WFOME) from crude waste frying oil (WFO). Taguchi method optimization was performed to identify the best set of reaction temperature, time, catalyst loading and methanol to WFO molar ratio for maximum WFOME yield. A catalyst composite material (CCM) which is a mixture of CH char and KNO3 (0–65 wt%) was calcined to obtain the catalyst. The KNO3 loading and CCM calcination time effects on the catalyst performance and physicochemical properties were examined. The combustion behavior of the CH and CCMs was investigated using thermal analysis techniques. Utilizing FTIR, XRD, BET, SEM, and pH measurements, the catalyst characterization was carried out. For analytical sample sizes (during thermal analysis) with high KNO3 loading, the thermal reactivity was higher. However, for larger sample sizes (during catalyst synthesis) higher KNO3 loading decreased the CCM global thermal reactivity due to an oxygen permeation resisting ash deposition on the top surface. Thus, KNO3 tuned the catalyst’s physicochemical properties as a function of its loading (optimum 45 wt%) by affecting the combustion characteristics of the CCMs and basic site concentration. The optimum WFOME yield was 97.99 wt% at a reaction temperature of 65 °C, a reaction time of 1.13 h, a catalyst loading of 5.42 wt%, and a methanol to WFO molar ratio of 13.55:1. The WFOME yield was dropped by 46.93 wt% in three consecutive catalyst reuse tests because of active components leaching.

Abstract Purpose This study aims to screen bacterial isolates from the Addis Ababa municipal solid waste dumping site (Koshe) for the biodegradation of low-density polyethylene bags and analyzes their efficiency in degrading plastic bags. Methods In this study, low-density polyethylene bag-degrading bacteria were isolated from the Koshe municipal solid waste disposal area in Addis Ababa, Ethiopia. Screening of isolates for low-density polyethylene bag biodegradation was carried out using a clear zone method. Additionally, the efficiency of the isolates for low-density polyethylene biodegradation was evaluated using the weight loss method, scanning electron microscopy analysis, and Fourier transform infrared analysis. Finally, molecular identification of potential low-density polyethylene degrader bacterial isolates was done by 16S rDNA sequencing. Results Isolates KS35, KS14, and KS119 resulted in significant weight loss of low-density polyethylene film (42.87 ± 1.91%, 37.2 ± 3.06%, and 23.87 ± 0.11% weight loss, respectively). These isolates were selected for further biodegradation study using scanning electron microscopy and Fourier transform infrared analysis. Scanning electron microscopy analysis shows the formation of pores, pits, and distortion of the plastic surface. Fourier transform infrared analysis indicates the appearance of new peaks at the surface of low-density polyethylene films. Phylogenetic analysis of the three potential bacterial isolates was also carried out, and the result indicates that the sequence of isolate KS35 had 99% similarity with sequences of Methylobacterium radiotolerans MN525302. Isolate KS119 had 100% similarity with Methylobacterium fujisawaense KT720189, and the sequence of isolate KS14 had 99% similarity with species of Lysinibacillus fusiformis. Conclusions Weight loss, scanning electron microscopy analysis, and Fourier transform infrared analysis results show that isolates KS35, KS14, and KS119 have high potential in degrading low-density polyethylene bags.

This study aimed to isolate lactic acid bacteria (LAB) from a traditional Ethiopian fermented product, Tella, and evaluate their functional properties. Of forty-three isolates, seven LAB were screened and identified as Pediococcus pentosaceus, Latilactobacillus curvatus, Leuconostoc mesenteroides, and Lactiplantibacillus plantarum species. The isolates were tested for their alcohol tolerance, acid and bile resistance, auto-aggregation, co-aggregation, hydrophobicity, antibacterial activity, and antibiotic susceptibility. LAB isolates, specifically P. pentosaceus TAA01, L. mesenteroides TDB22, and L. plantarum TDM41, showed a higher degree of alcohol tolerance in 8% and 10% (w/v) ethanol concentrations. Additionally, these three isolates displayed survival rates >85% in both acidic pH and bile environments. Among the isolates, L. plantarum TDM41 demonstrated the highest auto-aggregation, co-aggregation, and hydrophobicity with (44.9 ± 1.7)%, (41.4 ± 0.2)%, and (52.1 ± 0.1)% values, respectively. The cell-free supernatant of the isolates exhibited antibacterial activity against foodborne pathogens of Escherichia coli, Salmonella Enteritidis, and Staphylococcus aureus. Each isolate exhibited various levels of resistance and susceptibility to seven antibiotics and resistance was observed against four of the antibiotics tested. After performing a principal component analysis, Pediococcus pentosaceus TAA01, L. mesenteroides TDB22, and L. plantarum TDM41 were selected as the most promising ethanol-tolerant probiotic isolates.

The aim of this study was kinetic investigations of aluminum extraction from Ethiopian kaolinite with hydrochloric acid. The effects of extraction parameters, namely, solid-to-liquid ratio (0.05, 0.075, 0.100, and 0.125 g·mL−1), acid concentrations (2, 3, 4, and 5 M), reaction temperature (50, 60, 70, and 80°C), and time (20, 40, 60, 80, 100, 120, 140, 160, and 180 min), on yield of aluminum were investigated. The results revealed that the extraction yield of aluminum increased with increase of acid concentration, reaction temperature, and time and declined with increase of solid-to-liquid ratio. The kinetic analysis of aluminum extraction was evaluated using pseudohomogeneous, nucleation growth (Avrami), and shrinking core models. The results showed that kinetics of aluminum extraction were controlled by surface chemical reaction. The experimental results were well fitted by the shrinking core model of surface chemical reaction with first-order rate. The activation energy and the preexponential factor were 25.40 kJ·mol−1 and 0.949 cm·min−1, respectively. The leached solution samples were crystallized using evaporation and concentrated hydrochloric acid pouring. The volume ratios of concentrated hydrochloric acid to the samples were from 0.30 to 0.90 (v/v). The crystallization efficiency of aluminum chloride hexahydrate crystals increased with volume of hydrochloric acid and crystallization time. The crystallization yield of aluminum chloride hexahydrate crystals reached 90%. This study’s results clearly revealed that Ethiopian kaolinite could be a promising raw material to produce aluminum chloride hexahydrate, which could be used for water treatment application.

Kaolinite, a clay mineral, is an important industrial mineral which was gainfully utilized with several industrial significances. Towards mineral beneficiation, the present study aimed to investigate the effect of calcination temperature on the pozzolanic activity and specific surface area of Ethiopian kaolinite (Ek). The raw Ek and calcined Ek were characterized using different sophisticated techniques, such as XRD, FTIR, DSC, TGA, dynamic light scattering, electrophoretic light scattering, and SEM analysis. The pozzolanic activity and specific surface area of Ek particles were ascertained using Chapelle’s and Brunauer–Emmett–Teller methods, respectively, with some modifications. The results revealed that the calcination temperature had a great influence on pozzolanic activity and specific surface area of Ek. It was observed that the pozzolanic activity linearly increased with calcination temperature until 700°C and showed a maximal value of 1235 mg Ca(OH)2 g−1. On the other hand, beyond 700oC, the pozzolanic activity was inferred to be declined to 445 mg Ca(OH)2 g−1 at 1000°C due to agglomeration of calcined kaolinite (metakaolinite) and formation of spinel phase. A similar phenomenon was observed for specific surface area which increased with temperature until 700°C to exhibit the maximal values of 47.794 m2·g−1. Further, the investigation on zeta potential analysis showed that the magnitude value of the metakaolinite was observed to be less than the zeta potential value of the raw kaolinite, which indicated that the flocculation tendency of metakaolinite was greater than the kaolinite flocculation affinity in water.

The present study aimed to optimize the calcination process parameters (viz., temperature, time, and particles size) for the extraction of aluminum from Ethiopian kaolinite. The kaolinite calcination was done in the temperature of 600–700°C, time of 120–180 min, and particles size of 106–355 μm. The extraction of aluminum from calcined kaolinite was carried out at fixed acid concentration of 3 M, temperature of 80°C, liquid-to-solid ratio of 12 mL g−1, time of 120 min, and stirring speed of 700 rpm. The chemical composition of kaolinite was determined using XRF. Moreover, kaolinite, metakaolinite, and extracted aluminum were characterized by XRD, TGA, DSC, and FTIR. The XRF result of the kaolinite was mainly silicon oxide (55.76% w/w), aluminum oxide (32.02% w/w), and loss on ignition (11.17% w/w). Calcination of kaolinite produced amorphous metakaolinite due to the dehydroxylation reaction as shown by the FTIR results. Three endothermic peaks and one exothermic peak were detected in the thermal analysis of the kaolinite due to water removal, impurities decomposition, dehydroxylation reaction, and phase change from metakaolinite to spinel, respectively. The extracted aluminum proportionally increased with kaolinite calcination temperature and time. However, the extracted aluminum increased as the particles size reduced. The extracted aluminum was in the form of aluminum chloride hexahydrate and trigonal crystalline structure. The optimum values of the degree of conversion of kaolinite dehydroxylation reaction and extracted aluminum of 0.992 and 71.28% w/w were obtained at the optimum kaolinite calcination temperature of 700°C, time of 180 min, and particles size of 106 μm, respectively.