A Systematic Literature Review on Waste-to-Resource Potential of Palm Oil Clinker for Sustainable Engineering and Environmental Applications

Exposure of the static magnetic fields on the microbial growth rate and the sludge properties in the complete-mix activated sludge process (a Lab-scale study)

BACKGROUND

In this study, the effect of static magnetic fields (SMFs) on improving the performance of activated sludge process to enhance the higher rate of microbial growth biomass and improve sludge settling characteristics in real operation conditions of wastewater treatment plants has been investigated. The effect of SMFs (15 mT), hydraulic retention time, SRT, aeration time on mixed liquor suspended solids (MLSS) concentrations, mixed liquor volatile suspended solids (MLVSS) concentrations, α-factor, and pH in the complete-mix activated sludge (CMAS) process during 30 days of the operation, were evaluated.

RESULTS

There were not any differences between the concentration of MLSS in the case (2148.8 ± 235.6 mg/L) and control (2260.1 ± 296.0 mg/L) samples, however, the mean concentration of MLVSS in the case (1463.4 ± 419.2 mg/L) was more than the control samples (1244.1 ± 295.5 mg/L). Changes of the concentration of MLVSS over time, follow the first and second-order reaction with and without exposure of SMFs respectively. Moreover, the slope of the line and, the mean of α-factor in the case samples were 6.255 and, - 0.001 higher than the control samples, respectively. Changes in pH in both groups of the reactors were not observed. The size of the sluge flocs (1.28 µm) and, the spectra of amid I' (1440 cm-1) and II' (1650 cm-1) areas related to hydrogenase bond in the case samples were higher than the control samples.

CONCLUSIONS

SMFs have a potential to being considered as an alternative method to stimulate the microbial growth rate in the aeration reactors and produce bioflocs with the higher density in the second clarifiers.

Review of Geopolymer Nanocomposites: Novel Materials for Sustainable Development

The demand for geopolymer materials is constantly growing. This, in turn, translates into an increasing number of studies aimed at developing new approaches to the methodology of geopolymer synthesis. The range of potential applications of geopolymers can be increased by improving the properties of the components. Future directions of studies on geopolymer materials aim at developing geopolymers showing excellent mechanical properties but also demonstrating significant improvement in thermal, magnetic, or sorption characteristics. Additionally, the current efforts focus not only on the materials' properties but also on obtaining them as a result of environment-friendly approaches performed in line with circular economy assumptions. Scientists look for smart and economical solutions such that a small amount of the modifier will translate into a significant improvement in functional properties. Thus, special attention is paid to the application of nanomaterials. This article presents selected nanoparticles incorporated into geopolymer matrices, including carbon nanotubes, graphene, nanosilica, and titanium dioxide. The review was prepared employing scientific databases, with particular attention given to studies on geopolymer nanocomposites. The purpose of this review article is to discuss geopolymer nanocomposites in the context of a sustainable development approach. Importantly, the main focus is on the influence of these nanomaterials on the physicochemical properties of geopolymer nanocomposites. Such a combination of geopolymer technology and nanotechnology seems to be promising in terms of preparation of nanocomposites with a variety of potential uses.

Synthesis of Gum Arabic Magnetic Nanoparticles for Adsorptive Removal of Ciprofloxacin: Equilibrium, Kinetic, Thermodynamics Studies, and Optimization by Response Surface Methodology

Given the increasing risks that antibiotic abuse poses to microecology and human health, it is imperative to develop incredibly powerful adsorbents. This study investigated the use of environmentally sustainable polymeric nanocomposite based on gum arabic (GA) and magnetic nanoparticles (MNPs) synthesized via co-precipitation method to form gum arabic magnetitic nanoparticles (GA-MNPs) as an efficient adsorbent for ciprofloxacin (CIP) removal from aqueous solution. The physicochemical properties and morphology of the synthesized GA-MNPs were characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and Energy Dispersive X-Ray Analysis (EDX). The experiment was designed by response surface methodology (RSM) and the Central Composite Design (CCD) was utilized to optimize the operating variables: contact time (0–120 min), pH (3–10), adsorbent dosage (0.10–0.40 g/L), and concentration of adsorbate (5–100 mg/L). Results showed that 96.30% was the maximum percentage of CIP removed. The adsorption effect of the CIP molecule on the surface of the GA-MNPs was investigated using regression analysis and analysis of variance. Furthermore, Freundlich Isotherm and Pseudo Second order kinetic equations have the highest consistency with experimental investigations suggesting double-layer adsorption. This implies that chemisorption was the mechanism involved. In addition, the calculated thermodynamic parameters were postulating an exothermic and spontaneous method in nature. Owing to its adsorption selectivity and recyclability, GA-MNPs could be classified as an environmentally friendly, less expensive, and highly efficient promising adsorbent for remediation of CIP from aqueous solution.

Synthesis, Characterization, and Performance Evaluation of Hybrid Waste Sludge Biochar for COD and Color Removal from Agro-Industrial Effluent

Agro-waste management processes are evolving through the development of novel experimental approaches to understand the mechanisms in reducing their pollution levels efficiently and economically from industrial effluents. Agro-industrial effluent (AIE) from biorefineries that contain high concentrations of COD and color are discharged into the ecosystem. Thus, the AIE from these biorefineries requires treatment prior to discharge. Therefore, the effectiveness of a continuous flow bioreactor system (CFBS) in the treatment of AIE using hybrid waste sludge biochar (HWSB) was investigated. The use of a bioreactor with hydraulic retention time (HRT) of 1–3 days and AIE concentrations of 10–50% was used in experiments based on a statistical design. AIE concentration and HRT were optimized using response surface methodology (RSM) as the process variables. The performance of CFBS was analyzed in terms of COD and color removal. Findings indicated 76.52% and 66.97% reduction in COD and color, respectively. During biokinetic studies, the modified Stover models were found to be perfectly suited for the observed measurements with R2 values 0.9741 attained for COD. Maximum contaminants elimination was attained at 30% AIE and 2-day HRT. Thus, this study proves that the HWSB made from biomass waste can potentially help preserve nonrenewable resources and promote zero-waste attainment and principles of circular economy.

Adsorption Behavior of Methylene Blue Cationic Dye in Aqueous Solution Using Polypyrrole-Polyethylenimine Nano-Adsorbent

In this work, a polypyrrole-polyethyleneimine (PPy-PEI) nano-adsorbent was successfully synthesized for the removal of methylene blue (MB) from an aqueous solution. Synthetic dyes are among the most prevalent environmental contaminants. A new conducting polymer-based adsorbent called (PPy-PEI) was successfully produced using ammonium persulfate as an oxidant. The PEI hyper-branched polymer with terminal amino groups was added to the PPy adsorbent to provide more effective chelating sites for dyes. An efficient dye removal from an aqueous solution was demonstrated using a batch equilibrium technique that included a polyethyleneimine nano-adsorbent (PPy-PEI). The best adsorption parameters were measured at a 0.35 g dosage of adsorbent at a pH of 6.2 and a contact period of 40 min at room temperature. The produced PPy-PEI nano-adsorbent has an average particle size of 25–60 nm and a BET surface area of 17 m²/g. The results revealed that PPy-PEI nano-composite was synthesized, and adsorption was accomplished in the minimum amount of time. The maximum monolayer power, qmax, for MB was calculated using the isothermal adsorption data, which matched the Langmuir isotherm model, and the kinetic adsorption data, which more closely fitted the Langmuir pseudo-second-order kinetic model. The Langmuir model was used to calculate the maximum monolayer capacity, or qmax, for MB, which was found to be 183.3 mg g⁻¹. The as-prepared PPy-PEI nano-adsorbent totally removes the cationic dyes from the aqueous solution.

A review of ammonia removal using a biofilm-based reactor and its challenges

Extensive growth of industries leads to uncontrolled ammonia releases to environment. This can result in significant degradation of the aquatic ecology as well as significant health concerns for humans. Knowing the mechanism of ammonia elimination is the simplest approach to comprehending it. Ammonia has been commonly converted to less hazardous substances either in the form of nitrate or nitrogen gas. Ammonia has been converted into nitrite by ammonia-oxidizing bacteria and further reduced to nitrate by nitrite-oxidizing bacteria in aerobic conditions. Denitrification takes place in an anoxic phase and nitrate is converted into nitrogen gas. It is challenging to remove ammonia by employing technologies that do not incur particularly high costs. Thus, this review paper is focused on biofilm reactors that utilize the nitrification process. Many research publications and patents on biofilm wastewater treatment have been published. However, only a tiny percentage of these projects are for full-scale applications, and the majority of the work was completed within the last few decades. The physicochemical approaches such as ammonia adsorption, coagulation-flocculation, and membrane separation, as well as conventional biological treatments including activated sludge, microalgae, and bacteria biofilm, are briefly addressed in this review paper. The effectiveness of biofilm reactors in removing ammonia was compared, and the microbes that effectively remove ammonia were thoroughly discussed. Overall, biofilm reactors can remove up to 99.7% ammonia from streams with a concentration in range of 16-900 mg/L. As many challenges were identified for ammonia removal using biofilm at a commercial scale, this study offers future perspectives on how to address the most pressing biofilm issues. This review may also improve our understanding of biofilm technologies for the removal of ammonia as well as polishing unit in wastewater treatment plants for the water reuse and recycling, supporting the circular economy concept.

Blast Furnace Slag, Post-Industrial Waste or Valuable Building Materials with Remediation Potential?

In recent years, the construction industry has struggled with a variety of issues such as material availability, supply channel management, and the increasing cost of construction materials. These issues have encouraged the search for replacements and substitutes for existing construction materials. Blast Furnace Slag is used in the construction industry as a mineral amendment or aggregate. Their use in Earth Construction, due to their post-industrial origin, may be associated with increased levels of potentially toxic elements (PTE) in the soil. This study aimed to evaluate the effectiveness of the immobilization potential of Blast Furnace Slag and to compare it with the addition of Blast Furnace Slag with Activated Carbon using different concentrations of these amendments. We were able to determine the concentrations of selected PTE (zinc, copper, nickel, cadmium and lead) in the soil, roots and aerial parts of Lolium perenne L., using different concentrations of Blast Furnace Slag (3%, 5% and 10%), and Blast Furnace Slag with Activated Carbon (3% and 5%) as soil amendments. Measurements were carried out with Flame Atomic Absorption Spectrometry (FAAS). Both the addition of Blast Furnace Slag and Activated Carbon with Slag increased plant biomass. The addition of slag effectively reduced the zinc, copper, cadmium and lead content of the soil, while the addition of Activated Carbon slag significantly increased the content of selected PETs in the roots and aerial parts of plants. It was considered reasonable to use Blast Furnace Slag with the addition of Activated Carbon in supporting the processes of the assisted phytostabilization of PTE polluted soils.

Ductility Enhancement of Sustainable Fibrous-Reinforced High-Strength Lightweight Concrete

To limit the cross-sectional size of concrete structures, high-strength, lightweight concrete is preferred for the design and construction of structural elements. However, the main drawback of high-strength, lightweight concrete is its brittleness over normal-weight concrete. The ductility of concrete is a crucial factor, which plays an important role when the concrete structures are subjected to extreme situations, such as earthquakes and wind. This study aims to improve the ductility of high-strength, lightweight concrete by incorporating steel fibers. The palm oil clinker (POC)-based, high-strength, lightweight concrete specimens reinforced with steel fibers were prepared and their ductility was systematically examined. POC was used as aggregates and supplementary cementitious materials. Steel fibers from 0–1.50% (by volume), with an increment of 0.5%, were used in the concrete mix. Compression ductility, displacement ductility and energy ductility were used as indicators to evaluate the enhancement of ductility. Moreover, the compressive strength, flexural strength, stress-strain behavior, modulus of elasticity, load-displacement characteristics, energy absorption capacity and deformability of the concrete samples were investigated. The compression ductility, displacement ductility and energy ductility indexes were found to be increased by up to 472%, 140% and 568% compared to the control specimens (concrete with 0% steel fibers), respectively. Moreover, the deformability and energy absorption capacity of the concrete were increased by up to 566% and 125%, respectively. Therefore, POC-based, high-strength, fibrous, lightweight concrete could perform better than conventional concrete under extreme loading conditions as it showed significantly higher ductility.