Potential of GTL-Derived Biosolids for Water Treatment: Fractionization, Leachate, and Environmental Risk Analysis

This study aims to understand the potential of using biosolids produced from the world’s largest gas-to-liquid (GTL) plant for water treatment applications. The metal fractionization of the two samples: raw biosolid (BS) and the pyrolyzed biosolid-BS char (BSC) (temperature: 450 °C, heating rate: 5 °C/min, residence time: 30 min) into exchangeables (F1), reducible (F2), oxidizable (F3), and residual (F4) were carried out following the Community Bureau of Reference (BCR) procedure. Characterization showed an increased carbon content and reduced oxygen content in the biochar sample. Additionally, the presence of calcium, magnesium, and iron were detected in smaller quantities in both samples. Based on the extraction results for metals, the environmental risk analysis was determined based on RAC (Risk Assessment Code) and PERI (Potential Ecological Risk Index) indices. Furthermore, leaching studies following the TCLP (Toxicity Characteristic Leaching Procedure) were conducted. The results prove that pyrolyzing stabilizes the metals present in the raw material as BS sample had high F1 fractions, and the BS char had a greater F4 fraction. While the RAC and PERI indices show that the pyrolyzed BS has a ‘low risk’, much reduced compared to the original BS sample, this is confirmed by the leaching studies that displayed minimal leaching from the pyrolyzed sample. Overall, this study proves that the GTL biosolids can best be applied for water treatment after pyrolysis

Life cycle assessment of biofuel production from waste date stones using conventional and microwave pyrolysis

Date palm trees play a crucial role in the provision of essential nutrition by producing date fruits and are widely cultivated in Qatar. The processing of date fruits generates substantial quantities of carbon-rich date stone possessing remarkable energy potential. This inherent energy can be harnessed by applying pyrolysis techniques, which facilitate the production of many products with commercial value. Despite being a novice process, microwave (MW) pyrolysis has emerged as a promising avenue for converting biomass waste into eco-friendly biofuels. Nonetheless, the adoption of this new approach necessitates a comprehensive exploration of its ecological implications, warranting a meticulous life-cycle analysis (LCA) to ascertain its environmental footprint. As a result, using GaBi software, this study compares the life-cycle environmental impact of conventional and microwave-aided pyrolysis processes of date stone waste. The study also assesses the techno-economic analysis of the two processes. The physical and thermal analyses of the date stone waste indicated that the biomass is a high-energy source (Net calorific value-15.6 MJ/kg). While the life-cycle assessment indicated that MW pyrolysis has a greater implication on climate change (14.94 % more), ozone depletion (14.29 % more), ionizing radiation (14.36 % more), and photochemical ozone production (14.44 % more) than conventional pyrolysis. This demonstrates that conventional pyrolysis is less harmful to the environment than MW pyrolysis. The techno-economic analysis infers that conventional pyrolysis mode is superior to MW pyrolysis for the valorisation of date stone waste in terms of profitability, financial stability, and overall success

Co-pyrolysis of biomass and binary single-use plastics: synergy, kinetics, and thermodynamics

Waste management is an increasing global concern due to the rise in urbanization and industrialization. This study examines the co-pyrolysis of date pits (DP) and single-use plastics (polypropylene-PP and Styrofoam-PS) as a way to create value-added products. Single, binary, and ternary mixtures were pyrolyzed at three different heating rates to understand the synergy, kinetics, and thermodynamics. The results showed positive synergy and reduced activation energies during co-pyrolysis, due to varying reaction mechanisms. The positive values of ∆H, ∆G, and negative ΔS indicate endothermic non-spontaneous reactions and disorder in the products instead of the reactants during pyrolysis. Future studies should explore upscaling this process for sustainable energy production

Removal of Methylene Blue from Water Using Magnetic GTL-Derived Biosolids: Study of Adsorption Isotherms and Kinetic Models

Global waste production is significantly rising with the increase in population. Efforts are being made to utilize waste in meaningful ways and increase its economic value. This research makes one such effort by utilizing gas-to-liquid (GTL)-derived biosolids, a significant waste produced from the wastewater treatment process. To understand the surface properties, the biosolid waste (BS) that is activated directly using potassium carbonate, labelled as KBS, has been characterized using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and Brunauer–Emmett–Teller (BET). The characterization shows that the surface area of BS increased from 0.010 to 156 m2/g upon activation. The EDS and XPS results show an increase in the metal content after activation (especially iron); additionally, XRD revealed the presence of magnetite and potassium iron oxide upon activation. Furthermore, the magnetic field was recorded to be 0.1 mT using a tesla meter. The magnetic properties present in the activated carbon show potential for pollutant removal. Adsorption studies of methylene blue using KBS show a maximum adsorption capacity of 59.27 mg/g; the adsorption process is rapid and reaches equilibrium after 9 h. Modelling using seven different isotherm and kinetic models reveals the best fit for the Langmuir-Freundlich and Diffusion-chemisorptionmodels, respectively. Additional thermodynamic calculations conclude the adsorption system to be exothermic, spontaneous, and favoring physisorption

Removal of Methylene Blue from Water Using Magnetic GTL-Derived Biosolids: Study of Adsorption Isotherms and Kinetic Models

Global waste production is significantly rising with the increase in population. Efforts are being made to utilize waste in meaningful ways and increase its economic value. This research makes one such effort by utilizing gas-to-liquid (GTL)-derived biosolids, a significant waste produced from the wastewater treatment process. To understand the surface properties, the biosolid waste (BS) that is activated directly using potassium carbonate, labelled as KBS, has been characterized using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), and Brunauer–Emmett–Teller (BET). The characterization shows that the surface area of BS increased from 0.010 to 156 m2/g upon activation. The EDS and XPS results show an increase in the metal content after activation (especially iron); additionally, XRD revealed the presence of magnetite and potassium iron oxide upon activation. Furthermore, the magnetic field was recorded to be 0.1 mT using a tesla meter. The magnetic properties present in the activated carbon show potential for pollutant removal. Adsorption studies of methylene blue using KBS show a maximum adsorption capacity of 59.27 mg/g; the adsorption process is rapid and reaches equilibrium after 9 h. Modelling using seven different isotherm and kinetic models reveals the best fit for the Langmuir-Freundlich and Diffusion-chemisorptionmodels, respectively. Additional thermodynamic calculations conclude the adsorption system to be exothermic, spontaneous, and favoring physisorption

Food waste biochar: a sustainable solution for agriculture application and soil–water remediation

Abstract Biochar is a promising pyrolysed carbon-enriched soil amendment and has excellent properties for agriculture production and to remediate environmental pollution. A set of reviews were conducted on biochar production by pyrolysis process from various waste biomass which has drawn extensive interest due to the low cost of production with several benefits. As many potential technologies have been developed, there are still several knowledge gaps that have been identified for some key points to contribute a comprehensive study towards soil fertility, nutrient and water retention, soil microbial activity, plant growth and yield, pollution remediation, mitigation of greenhouse gas emission and an improvement in the farmer’s economy to achieve maximum profit by adopting environmentally friendly technique “pyrolysis”. Therefore, this review explored a detailed study on food waste biochar production by the pyrolysis process and its impact on different applications as an amendment. Slow pyrolysis process at low and medium temperatures is a potential amendment for agriculture production and soil and water remediation by enhancing biochar properties like carbon, BET surface area, cation exchange capacity, zeta potential, and nutrient content, etc. with minimum ash content. The biochar enhances soil water and nutrient retention capacity, crop yield, and improved microbial community at different soil quality. Additionally, food waste to biochar is a realistic adsorbent and economical carbon sequester to mitigate GHG emissions. This review conducted a brief assessment of the knowledge gaps and future research directions for researchers, encouraging investigators, stakeholders, and policymakers to make the best possible decision for food waste valorization

Biochar from food waste: a sustainable amendment to reduce water stress and improve the growth of chickpea plants

The application of biochar in agriculture is a developing means to improve soil water retention, fertility, and crop yield. The present work focuses on biochar preparation from mixed vegetable and fruit wastes, using cauliflower, cabbage, banana peels, corn leaves, and corn cobs. The biochar produced at 400 °C was applied to the soil as an amendment to observe the qualitative changes of soil quality, plant growth, and water retention capacity of the soil based on screening in a previous study. Pot experiments were conducted at a laboratory scale having 0%, 2%, and 6% biochar mixed with sand. Each pot was sown with seeds of chickpeas (Cicer arietinum L.) and monitored over 60 days. Two biochar application rates improved soil quality by increasing soil porosity from 49.3 to ≥ 53.4%, more than doubling cation exchange capacity to ≥ 21.1 cmolc.kg−1, providing a small reduction in bulk density of approximately 10% and decreasing electrical conductivity of the extract by at least 40% in comparison to control condition. The biochar application also increased key soil nutrients K, Mn, S, and P by a factor of 2–9 times. Application of biochar at 2% and 6% improved water retention from 55 to 77 and 91 mL respectively over the study and, more importantly, more than doubled the biomass yield for the same water application. The lower biochar application rate of 2% led to more germinated seeds (p = 0.0001), leaves (p = 0.0001), flowers, and fruiting chickpeas than the control condition. The 6% biochar application rate slightly improved plant height (p = 0.01) and provided a small reduction in water loss compared with the 2% biochar. Both biochar loadings increased the root and shoot biomass (p = 0.005) and nutrient content of the shoot and root biomass, particularly K, P, and S (p = 0.0001). This study demonstrates that biochar application at 2–6% is an effective means to increase chickpea yield and reduce water stress. Given small differences in performance within this application range, 2% application is recommended. The study establishes valorization of cellulose rich food waste in the form of biochar as a potential method for positive soil management and increased agricultural productivity in arid environments.Other Information Published in: Biomass Conversion and Biorefinery License: https://creativecommons.org/licenses/by/4.0See article on publisher's website: http://dx.doi.org/10.1007/s13399-022-02575-1</p

Adsorbent-Embedded Polymeric Membranes for Efficient Dye-Water Treatment

Traditional bulk adsorbents, employed for the removal of dyes and metal ions, often face the drawback of requiring an additional filtration system to separate the filtrate from the adsorbent. In this study, we address this limitation by embedding the adsorbent into the polymer matrix through a process involving dissolution–dispersion, spin-casting, and heat-stretching. Selective dissolution and dispersion facilitate the integration of the adsorbent into the polymer matrix. Meanwhile, spin-casting ensures the formation of a uniform and thin film structure, whereas heat-induced stretching produces a porous matrix with a reduced water contact angle. The adsorbent selectively captures dye molecules, while the porous structure contributes to water permeability. We utilized inexpensive and readily available materials, such as waste polyethylene and calcium carbonate, to fabricate membranes for the removal of methylene blue dye. The effects of various parameters, such as polymer-adsorbent ratio, initial dye concentration, and annealing temperature, were investigated. Equilibrium data were fitted to Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherms. The equilibrium data were best represented by the Langmuir isotherm, with maximum adsorption capacity of 35 mg/g and 43 mg/g at 25 °C and 45 °C, respectively. The membranes can be regenerated and recycled with a 97% dye removal efficiency. The study aims to present a template for adsorbent-embedded polymeric membranes for dye removal, in which adsorbent can be tailored to enhance adsorption capacity and efficiency

Biochar from vegetable wastes: agro-environmental characterization

Considering the global issue of vegetable wastes generation and its impact on the environment and resources, this study evaluated the conversion of four largely produced vegetable wastes (cauliflower, cabbage, banana peels and corn cob residues) into biochar. Each waste was tested individually and as a combined blend to assess feedstock influences on biochar properties. In addition, various pyrolysis temperatures ranging from 300 °C to 600 °C and two particle size fractions (less than 75 µm, 75–125 µm) were considered. Biochars were characterized for various properties that can influence the biochars’ effectiveness as a soil amendment. It was found that pyrolysis temperature was the most dominant factor on biochar properties, but that individual feedstocks produced biochars with different characteristics. The biochars had characteristics that varied as follows: pH 7.2–11.6, ECE 0.15–1.00 mS cm−1, CEC 17–cmolc kg−1 and ζ-potential − 0.24 to − 43 mV. Based on optimal values of these parameters from the literature, cauliflower and banana peels were determined to be the best feedstocks, though mixed vegetable waste also produced good characteristics. The optimum temperature for pyrolysis was around 400 °C, but differed slightly (300–500 °C) depending on the distinct feedstock. However, smaller particle size of biochar application was always optimal. Biochar yields were in the range of 20–30% at this temperature range, except for corn cobs which were higher. This study demonstrates that pyrolysis of dried vegetable wastes is a suitable waste valorization approach to produce biochar with good agricultural properties.Other Information Published in: Biochar License: https://creativecommons.org/licenses/by/4.0See article on publisher's website: http://dx.doi.org/10.1007/s42773-020-00069-9</p

A facile energy-efficient approach to prepare super oil-sorbent thin films

Oil spills on water surface and shoreline have caused significant water pollution, and one of the ways to deal with them is to use oil sorbents. An effective sorbent provides high oil uptake and retention values, high selectivity, super-fast uptake kinetics, and sufficient mechanical strength to ensure practical application under different conditions. In this regard, synthetic sorbents made up of graphene, carbon nanotubes, and polymers in the form of aerogels, thin films, pads, and non-woven fibers have been widely explored. However, none of them addresses all the attributes of an ideal oil sorbent. Aerogels provide extremely high uptake values, but they are so light that it is difficult for the end user to handle them. On the other hand, thin films and non-woven fibers can quickly absorb oil but suffer from low uptake capacity with low retention values. Similarly, commercial oil sorbent pads have sufficient mechanical strength, but low uptake capacity compared to aerogels. Herein, we present a super oil sorbent with a porous structure using a facile energy-efficient approach. The as-prepared sorbent comprises a porous thin film with micropores and macro-cavities, resulting in super-fast uptake kinetics and a high oil uptake value of 85 g/g. Moreover, tensile test results confirm sorbent’s effectiveness in spill response. Lastly, our unique design does not involve expensive hydrophobic functionalization and thus utilizes lower embodied energy and generates lower carbon footprints