Optimization of synthesis and separation performance of nanotube-infused polysulfone membrane with polyvinyl alcohol layer to separate oil-containing wastewater

Wastewater is one of the major problems to human life because it contains contaminants (such as viruses, worms, bacteria, etc.) which pollute the environment and causes various diseases (like cholera, dehydration, skin disease, eye disease, etc.) that are dangerous to human being. Various industries generate high volumes of concentrated oil-water emulsion containing wastewater on a daily basis. Therefore, it is important to reduce the concentration of oil in the oil-containing wastewater to an acceptable discharge limit before its disposal in order to avoid environmental pollution. In view of this, this project was aimed at optimising the synthesis and operational performance of the nanotube-infused polysulfone (PS) membrane with a polyvinyl alcohol layer to separate oil-containing wastewater. To achieve the afore-mentioned goal, first the carbon nanotubes (CNTs) were produced and infused into the membranes in order to increase their mechanical stabilities. The CNTs were produced using a vertical swirled fluid chemical vapour deposition (VSFCCVD) method at the temperature of 850oC. Ferrocene was used as both a catalyst and a source of carbon, nitrogen gas was run through the equipment in order to make sure that there were no gas leaks and that the contaminants (other unidentified/unknown gases) are removed from the system, and argon gas was used as a carrier. The CNTs were also functionalised and purified using various acids in order to increase their hydrophilic capability and to further enhance the mechanical stability of the membranes. The CNTs were characterised using the transmission electron microscope (TEM), thermogravimetric analysis (TGA), X-ray diffraction spectroscopy (XRD), Raman spectroscopy and many other characterisation methods. The as-produced and the purified CNTs were blended in 20% polysulfone solution. Seven membranes were synthesised using the phase immersion inversion method. A polyvinyl alcohol layer was used to further improve the hydrophilicity and the mechanical stability of the membrane. The improved mechanical stability and hydrophilicity of the membrane, minimises fouling and concentration polarisation on the membrane. The membranes were characterised using the Fourier transform infrared spectroscopy (FTIR), contact angle, Braunner-Emmet-Teller (BET) and the scanning electron microscope (SEM). The separation performance of the membrane was tested using real industrial oil-containing wastewater. It is known that ferrocene can be used as both a catalyst and source of carbon as it has produced multi-walled CNTs with the lengths that are between 450-850 nm long. The mixture of nitric acid and sulphuric acid in a ratio of 1:3 was able to remove about 59% of the ferrocene catalyst particles during functionalization of CNTs. Hydrofluoric acid, hydrochloric acid together with the oxidation process removed about 99% of the contaminated impurity catalyst particles during the purification of CNTs. The use of 20% PS solution improved the quality but reduced the porosity which in turn reduced the membrane’s flux but maintained the separation performance of the membrane since all membranes have rejected the concentration of oil in the retentate of over 82%. BET gave the average pore sizes that ranged between 11 and 24 nm which are capable of rejecting oil droplets of the industrial oil-containing wastewater with diameter that ranges between 0.02-0.2 μm. During the separation performance evaluation using the oil-containing wastewater, all the membranes tested gave excellent results with high throughput and oil rejections that ranged between 82 and 95%. This was due to the polyvinyl alcohol (PVA) hydrophilic layer that all membranes possessed. These rejections were consistent with those obtained when the synthetic oil-containing wastewater was used. However, unlike when the synthetic oil-water was used, all membranes did not meet the acceptable discharge limit as they showed the concentration of oil in the permeate that ranged between 16 and 64 mg/L at flow rates ranging between 46.8 and 52.2 L/h. The best performing membrane using the as-produced CNTs was 5% CNTs with the rejection of oil in the retentate that ranged between 18 and 52 mg/L at the afore-mentioned flow rates. The as-produced infused membranes were those membranes that their separation performance was first tested using the synthetic oil-containing wastewater. This indicated that the performance of the membrane increases with a decrease in the concentration of the as-produced CNTs as well as the membrane’s flux. The overall best performing membrane was p7.5% CNTs (membrane infused with 7.5% of purified CNTs) with oil rejections ranging between 94.9 and 95.7%. The permeate showed the oil concentration that ranged between 16 and 19 mg/L at the mentioned flow rates. This was due to the purified CNTs which further increased the hydrophilicity of the membranes. These results showed that the performance of the polysulfone is directly related to the concentration of oil in the permeate and inversely related to the increase of the concentration of oil in the permeate, the flow rate as well as the membrane’s flux. The utilisation of the purified CNTs increases the hydrophilicity which in turn improves the fouling resistance and enhances the mechanical stability of the membrane. Thus the separation performance of the PS membrane with the PVA layer and the purified CNTs is greater than that with the infused as-produced/non-purified CNTs

Mineralization and N-use efficiency of tree legume prunings from fertilizer tree systems and low quality crop residues in Malawi

There is substantial evidence that fertilizer tree systems are capable of maintaining increased and sustainable crop production on low fertility soils in southern Africa, thus reducing the required amount of chemical fertilizer. However, crop yield increase in soils amended by fertilizer tree systems can only be optimized if nutrient release by the organic materials and nutrient demand by the crop are in synchrony. The decomposition and N release patterns of high quality tree prunings (gliricidia and sesbania) and crop residues (pigeon pea leaves and roots, and maize stover) were studied to understand the N use efficiency of fertilizer tree systems. The treatment were (1) quality pruning residues from gliricidia (Gs) and sesbania (Ss), (2) three medium quality residue levels including pigeon pea leaves (Pea-L), pigeon pea leaves + roots (Pea-LR) and pigeon pea roots (Pea-R), and (3) two rates of maize stover (Stover-1 and Stover-2) as low quality residues, and control (no crop residues, no tree prunings). The treatment combinations were laid out as a randomized complete blocks design. Mixtures of tree prunings with 2.5 t ha-1 maize stover increased maize N uptake and grain yield whereas 5 t ha-1 maize stover reduced maize N uptake and grain yield during the wetter season. Mixtures of Pea-R, Stover-1 or Stover-2 with tree prunings depressed yields during the drier season. Stover-2 had the highest N fraction immobilized N, respectively 15 and 35% N during the wetter and drier conditions. Weconclude that (1) mixing of high quality tree prunings with crop residues may enhance the decomposition of low quality crop residues but there is no special interaction, and (2) remineralization of N immobilized early in the season by the low quality organic materials is stimulated by welldistributed rainfall

Status of biofertilizer research, commercialization, and practical applications: A global perspective

This book chapter published by Elsevier Inc., 2021Most contemporary agricultural practices involve the use of synthetic fertilizers which have been linked to numerous deleterious consequences such as eutrophication of water bodies and emission of greenhouse gases. Biofertilizers offer viable and environmentally friendly alternatives. The positive effects of plant growth-promoting rhizobacteria have extensively been demonstrated several agronomically important crops under both controlled and field conditions. Despite the large volume of literature documenting the potential of these microbial inoculants as biofertilizers, their practical application has largely been hampered by several factors. This chapter presents the current knowledge of biofertilizer research, commercialization, and practical applications from the global perspective. The constraints facing their research and global application are also articulated. Finally, some prospects regarding their future research, commercialization and practical application for sustainable cropping systems are critically elucidated. It is anticipated that this will enable the full evaluation of the potential prospects of biofertilizers for sustainable agriculture and ecosystems globally

Sustainable Food Production Systems for Climate Change Mitigation: Indigenous Rhizobacteria for Potato Bio-fertilization in Tanzania

The global rise in human population has led to the intensification of agricultural activities to meet the ever-rising food demand. The potato (Solanum tuberosum L.) is a crop with the potential to tackle food security issues in developing countries due to its short growth cycle and high nutrient value. However, its cultivation is heavily dependent on artificial fertilizers for yield maximization which culminates in global warming and other environmental problems. There is need, therefore, for its alternative fertilization technologies to mitigate climate change. This study evaluated the potential of indigenous rhizobacteria for potato cropping in Tanzania. Ten potato rhizobacterial isolates belonging to Enterobacter, Klebsiella, Citrobacter, Serratia, and Enterobacter genera were obtained from a previous collection from different agro-ecological areas in Tanzania. The isolates were characterized culturally, microscopically, biochemically, and by their carbohydrate utilization patterns. Their in vitro plant growth-promoting (PGP) traits such as nitrogen fixation, solubilization of phosphates, potassium, and zinc, and production of siderophores, indole acetic acid, and gibberellic acids were then evaluated. Lastly, sterilized potato seed tubers were bacterized with the inoculants and grown in pots of sterile soil in a screen-house using untreated plants as a control experiment. The potato rhizobacterial isolates had varying characteristics and showed varying in vitro PGP activities. The screen-house experiment also showed that the rhizobacterial treatments significantly ( p < 0.05) enhanced different parameters associated with potato growth by up to 91% and established the potential of most of the isolates as alternative biofertilizers in potato cropping systems in Tanzania.This research article published by Springer Nature, 202

Effects of Carrier Materials and Storage Temperatures on the Viability and Stability of Three Biofertilizer Inoculants Obtained from Potato (Solanum tuberosum L.) Rhizosphere

This research article was published by MDPI in 2022Biofertilizer technology continues to be derailed by the short shelf life of inoculants. The present study investigated the suitability of wheat-bran (WB), rice-husks (RH), farmyard-manure (FYM), bagasse (BG), and sawdust (SD) in the formulation of potato-derived Klebsiella grimontii (MPUS7), Serratia marcescens (NGAS9), and Citrobacter freundii (LUTT5) under refrigerated (8 °C) and room (25 ± 2 °C) storage. The physicochemical properties of the materials were assessed before sterilization and introduction of the inoculants and assessment of their viability for 8 months. Most of the physicochemical properties of the materials varied significantly (p < 0.05). Bagasse supported the maximum growth of MPUS7 (5.331 log CFU g−1) under refrigeration and LUTT5 (4.094 log CFU g−1) under both conditions. Under room storage, the maximum growth of MPUS7 (3.721 log CFU g−1) occurred in WB. Formulations that remained viable under room storage can easily be integrated into existing agricultural distribution systems that lack refrigeration

Endophytic Rhizobacteria for Mineral Nutrients Acquisition in Plants: Possible Functions and Ecological Advantages

This book chapter published by Springer Nature Switzerland AG., 2021Nutrient-deficiency in agricultural soils is a major problem in many parts of the world, it is, therefore, artificial fertilizers are widely used to boost crop production. Unfortunately, these fertilizers are associated with a myriad of environmental problems hence, there is a need for viable alternatives. The realization that the plant microbiome can improve plant health, soil fertility, and crop productivity is one of the most fascinating scientific discoveries in the world. For several decades, rhizobacteria have been studied due to their various plant growth-promoting (PGP) traits. Endophytic rhizobacteria are unique plant microbiome that establish themselves within plant root tissues and exert beneficial functions to their hosts without harming them. A lot of emphases have been put on these bacteria as viable tools for sustainable agriculture and it is advanced that they could be better plant growth promoters than their external counterparts. However, this theory is not yet clearly understood. This chapter provides the current state of understanding of the putative functions of endophytic rhizobacteria and their future prospects for plant mineral nutrients acquisition. Their advantageous traits that largely advanced to facilitate these PGP functions are also discussed. Such informations can provide better opportunities for improved plant mineral nutrients acquisition and enhance the application of these microbes as viable strategies for sustainable agriculture

Molecular Identification and In Vitro Plant Growth-Promoting Activities of Culturable Potato (Solanum tuberosum L.) Rhizobacteria in Tanzania

This research article published by Springer Nature Switzerland AG., 2020The present study investigated the diversity of culturable rhizobacteria associated with potato (S. tuberosum L.) in Tanzania and assessed their in vitro plant growth-promoting (PGP) activities to deduce their potential as biofertilizers. Potato rhizosphere soil and tuber samples (54 samples in total) were collected from 9 villages in three different agro-ecological regions in Tanzania. A total of 145 rhizobacterial isolates were obtained, 52 of which were selected and identified by partial 16S rRNA gene sequences and screened for various PGP traits in vitro including qualitative and quantitative solubilization of phosphorus (P), zinc (Zn) and potassium (K), nitrogen (N2) fixation and production of ammonia (NH3) in nitrogen-free medium, and indole-3-acetic acid (IAA), gibberellic acids (GA) and siderophores production. The results showed that the isolates were all Gammaproteobacteria, belonging to 4 families (Enterobacteriaceae, Yersiniaceae, Pseudomonadaceae and Morganellaceae) and 9 genera (Enterobacter, Klebsiella, Serratia, Pseudomonas, Morganella, Buttiauxella, Pantoea and Cedecea). Significant differences (P < 0.05) were observed for all assessed PGP abilities of the external and endophytic rhizobacterial isolates except for quantitative siderophore production and qualitative P and K solubilization for the external rhizobacteria and production of IAA and GA for the endophytic rhizobacteria. Among the best PGP isolates which can be exploited for biofertilization of the potato were Klebsiella pneumoniae KIBS1, K. grimontii LUTS10, Serratia liquefaciens KIBT1, Enterobacter ludwigii KIBS10 and Citrobacter freundii MWALS6. Comparative evaluation of PGP abilities of these two groups of isolates revealed significant differences (P < 0.05) only for NH3 and IAA production and qualitative K solubilization

Mitigation of Acrylamide in Foods: An African Perspective

Acrylamide (ACR) is a possible human carcinogen, with neurotoxic properties. It is a heat-generated food toxicant particularly found in carbohydrate-rich foods. Its occurrence is of global concern and constitutes a major challenge to food safety, due to its presence in several thermally processed foods worldwide. Since its discovery, ACR has been recognized as one of the most widely investigated heat-induced food contaminant, and several reports on its formation and occurrence since its discovery have been reported. However, information on the extent of ACR occurrence in foods consumed in different parts of Africa is rather too limited. This is particularly a concern considering that most carbohydrate-based foods, subjected to varying degrees of thermal processing, are consumed as staple diets almost on daily basis in the continent. As such, African populations may be exposed to high levels of ACR daily. Thus, this chapter covers the formation, occurrence and health impact of ACR in foods. It further summarizes previous studies looking at ACR reduction and mitigation strategies, especially those that may be applicable in the continent. Adequate sensitization of the populace about the prevention of ACR as a food contaminant is essential to ensure the safety of heat-processed carbohydrate-rich foods in the continent

Whole-Genome Sequences of Three Plant Growth-Promoting Rhizobacteria Isolated from Solanum tuberosum L. Rhizosphere in Tanzania.

This research article published by the American Society for Microbiology, 2020We present here the complete genome sequences of plant growth-promoting sp. strain MPUS7, sp. strain NGAS9, and sp. strain LUTT5, isolated from rhizosphere soils and tubers of potato ( L.) plants growing in the northern and southern highlands of Tanzania

Agroforestry with N2-fixing trees: sustainable development's friend or foe?

Legume tree-based farming systems sit at a crucial nexus of agroecological sustainability. Their capacity to support microbial N2 fixation can increase soil nitrogen (N) availability and therefore improve soil fertility, crop yields, and support long-term stewardship of natural resources. However, increasing N availability oftentimes catalyzes the release of N into the surrounding environment, in particular nitrous oxide (N2O)—a potent greenhouse gas. We summarize current knowledge on the agroecological footprint of legume-based agroforestry and provide a first appraisal of whether the technology represents a pathway toward sustainable development or an environmental hazard