Continuous fixed-bed column study and adsorption modeling removal of Ni2+, Cu2+, Zn2+ and Cd2+ ions from synthetic acid mine drainage by nanocomposite cellulose hydrogel

Application of machine learning for environmentally friendly advancement: exploring biomass-derived materials in wastewater treatment and agricultural sector - a review

There are several uses for biomass-derived materials (BDMs) in the irrigation and farming industries. To solve problems with material, process, and supply chain design, BDM systems have started to use machine learning (ML), a new technique approach. This study examined articles published since 2015 to understand better the current status, future possibilities, and capabilities of ML in supporting environmentally friendly development and BDM applications. Previous ML applications were classified into three categories according to their objectives: material and process design, performance prediction and sustainability evaluation. ML helps optimize BDMs systems, predict material properties and performance, reverse engineering, and solve data difficulties in sustainability evaluations. Ensemble models and cutting-edge Neural Networks operate satisfactorily on these datasets and are easily generalized. Ensemble and neural network models have poor interpretability, and there have not been any studies in sustainability assessment that consider geo-temporal dynamics; thus, building ML methods for BDM systems is currently not practical. Future ML research for BDM systems should follow a workflow. Investigating the potential uses of ML in BDM system optimization, evaluation and sustainable development requires further investigation.

Bacterial biomineralization of heavy metals and its influencing factors for metal bioremediation

Increasing industrial pollution and certain hazardous agricultural practices have led to the discharge of heavy toxic metals into the environment. Among different bioremediation techniques, biomineralization is the synthesis of biomineral crystals extracellularly or intracellularly. Several bacteria, such as Bacillus cereus, Pseudomonas stutzeri, Bacillus subtilis, and Lactobacillus sphaericus have been found to induce heavy metal precipitation and mineralization for bioremediation. This article summarizes the different biomineralization mechanisms of bacterial-induced heavy metal biomineralization, mainly microbial-induced carbonate precipitation (MICP), microbial-induced phosphate precipitation (MIPP), and microbial-induced sulphide precipitation (MISP). Moreover, bacterial structures such as cell wall, biofilm, and extracellular polymeric substances (EPS) influence mineralization and control bacterial compartmentalization of heavy metal precipitation. Several genes control the efficiency of biomineralization in bacteria, such as ureA, ureB, ureC, phoA, dsrA, dsrB, dsrC, dsrD, dsrE, luxS, and ompR. This biomineralization mechanism provides new and broad prospects for its application in soil improvement, industrial applications, and wastewater treatments. In addition, bacterial genetic modification holds immense potential for advancing the biomineralization process to meet diverse environmental and industrial needs.

Modeling of the biomethane production from ultrasonic pretreated fruit and vegetable waste via anaerobic digestion

The global dependency on the depleted fossil fuels has led to the quest for acquiring alternative energy sources. Different types of waste material are generated at a high rate and tapping into their use for greener, alternative energy production is an option. The mesophilic anaerobic co-digestion of fruit and vegetable waste and wastewater treatment plant sewage sludge experiments were conducted using ultrasonic pretreated substrates. Sonication exposure times from 0 to 45 min were selected for the experiments. An automatic methane potential test system (BMP) was used to determine the production rate of biomethane of the fruit and vegetables waste containing 60% fruit and 40% vegetables. The highest cumulative methane production of 238 mL g-1 VS was achieved at sonication time exposure of 45 min. It was observed that an increase in ultrasonic sonication exposure time, improved methane yield. The resulting experimental data was fitted with the modified Gompertz, co-digestion modified Gompertz, original Richards, modified Richards and co-digestion modified Richards models. IBM SPSS Statistics software was used for curve fitting and the estimation of the models' kinetic parameters. The modified Gompertz and Richards models showed higher goodness fit, both with R2 of 0.93 and modified Richards models did not produce a good fit for the data, with R2 of 0.7. The developed co-digestion models considered a combination of substrates that were easily digested as well as complex substrates that required multiple steps of digestion. The results show that the co-digestion modified Gompertz model had a goodness of fit of 0.98. Co-digestion modified Richard's model perfectly fit the experimental data, with R2 of 1. Both the co-digestion modified models are recommended due to their fitting performance. Fruit and vegetable waste comprise multiple substrates including simple sugars that digest readily and much more complex cellulose substrates that require more steps to digest and requiring the second step of digestion after undergoing hydrolysis. Both models took that into account. The aim of this study was to evaluate the suitability of the Gompertz and Richards model in the co-digestion of fruit and vegetables waste with sludge, as well as to develop co-digestion models for the substrates at hand.

Immobilized chitosan as an efficient adsorbent for columnar adsorption of Cr (VI) from aqueous solution

The current effort focuses on creating an effective adsorbent for Cr (VI) adsorption due to the growing need to address Cr (VI) pollution in aqueous solutions. Chitosan, a biopolymer and polysaccharide with several functional sites, is immobilized on alginate using the ion exchange technique. Both prior to and following Cr (VI) adsorption, the material's shape, crystallinity, and functional groups are reported. Immobilized chitosan was employed to adsorb Cr (VI) in a fixed bed column with variable operational parameters (flow rate, initial chromium content, and bed height). The analysis of breakthrough curves showed that at a flow rate of 10 mL/min, Cr (VI) concentration of 50 mg/L and a bed height of 18 cm, a maximum adsorption of 78.41 % was achieved. The adsorption system and the breakthrough curves were thoroughly understood by using Thomas, Yoon-Nelson and Adams-Bohart kinetic models. There is promise for the large-scale use of synthesized immobilized chitosan because the current adsorption process fits the Thomas and Yoon-Nelson model well and confirms the homogenous bed, low mass transfer resistance, and constant operating conditions throughout the experiment. Furthermore, an exploration of the adsorption mechanism is undertaken and the outcomes are compared with existing literature. The regeneration and reuse tests up to four cycles provided insight into the immobilized chitosan's stability, dependability, and potential for scaling up.

The impact of ozone treatment on the removal effectiveness of various refractory compounds in wastewater from petroleum refineries

Large volumes of wastewater are generated during petroleum refining processes. Petroleum refinery wastewater (PRW) can contain highly toxic compounds that can harm the environment. These toxic compounds can be a challenge in biological treatment technologies due to the effects of these compounds on microorganisms. These challenges can be overcome by using ozone (O3) as a standalone or as a pretreatment to the biological treatment. Ozone was used in this study to degrade the organic pollutants in the heavily contaminated PRW from a refinery in Mpumalanga province of South Africa. The objective was achieved by treating the raw PRW using ozone at different ozone treatment times (15, 30, 45, and 60 min) at a fixed ozone concentration of 3.53 mg/dm3. The ozone treatment was carried out in a 2-liter custom-designed plexiglass cylindrical reactor. Ozone was generated from an Eco-Lab-24 corona discharge ozone generator using clean, dry air from the Afrox air cylinder as feed. The chemical oxygen demand, gas chromatograph characterization, and pH analysis were performed on the pretreated and post-treated PRW samples to ascertain the impact of the ozone treatment. The ozone treatment was effective in reducing the benzene, toluene, ethylbenzene, and xylenes (BTEX) compounds in the PRW. The 60-min ozone treatment of different BTEX pollutants in the PRW resulted in the following percentage reduction: benzene 95%, toluene 77%, m + p-xylene 70%, ethylbenzene 69%, and o-xylene 65%. This study has shown the success of using ozone in reducing the toxic BTEX compounds in a heavily contaminated PRW.

Review on Moringa oleifera, a green adsorbent for contaminants removal: characterization, prediction, modelling and optimization using Response Surface Methodology (RSM) and Artificial Neural Network (ANN)

Moringa oleifera utilization in water treatment to eliminate emerging pollutants such as heavy metal ions, pesticides, pharmaceuticals, and pigments has been extensively evaluated. The efficacy of Moringa oleifera biosorbent has been investigated in diverse research work using various techniques, including its adsorption capacity kinetic, thermodynamic evaluation, adsorbent modifications, and mechanism behind the adsorption process. The Langmuir isotherm provided the most remarkable experimental data fit for batch adsorption investigations, whereas the best fit was obtained with the pseudo-second order kinetic model. Furthermore, only a few papers that combined batch adsorption with fixed-bed column investigations were examined. In the latter articles, the scientists modified the adsorbent to increase the material's adsorption capacity as determined by analytical methods, including IR spectroscopy, scanning electronic microscope (SEM), and X-ray diffraction (XRD). However, the raw material can show appreciable adsorption capacity values, proving moringa's potency as a biosorbent. Hydrogen bonds, electrostatic interaction, and van der Waals forces were the main processes in the found and reported adsorbent-adsorbate interactions. These mechanisms could change depending on the physiochemical nature of adsorption. Although frequently employed for heavy metal ions and dye adsorption, Moringa oleifera can still be explored in pesticide and medication adsorption investigations due to the few publications in this comprehensive review. This study, therefore, examined different Adsorbents from the Moringa oleifera plant, as well as parameters and models for enhancing the adsorption process.

Design and Development of a Pilot-Scale Industrial Wastewater Treatment System with Plant Biomass and EDTA

The impact generated by the indiscriminate disposal of heavy metals into the different bodies of water is not only environmental but also social due to the health effects it produces in several organisms, including ourselves. Therefore, treatment systems around the world are the subject of continuous research to find treatment systems that are economical, efficient, and easy to implement in the industries that generate these increasingly harmful impacts on society and the environment in general. One way to design and develop systems of water treatment is that which takes advantage of the waste generated, such as the waste from the E. crassipes plant. The conditions of this plant make it perfect due to its abundant biomass and important content of cellulose and hemicellulose. Nevertheless, in almost all the investigations that characterize the way in which the biomass of this plant adsorbs heavy metals, it does so under laboratory conditions, being very far from the reality of industrial discharges. The objective of this project is to design and develop a pilot-scale industrial wastewater treatment system with plant biomass and EDTA. Three pilot-scale systems were built with EDTA-modified biomass in different concentrations, giving the parameters of the design for the development of a system that can treat around 80 L of Chromium (VI) contaminated water. This treatment system with E. crassipes biomass and EDTA with proportions of 9:1 costs around USD 10, which is quite cheap compared to conventional ones.

Preparation and modification of nanocellulose and its application to heavy metal adsorption: A review

Heavy metals are a notable pollutant in aquatic ecosystems that results in many deadly diseases of the human body after enrichment through the food chain. As an environmentally friendly renewable resource, nanocellulose can be competitive with other materials at removing heavy metal ions due to its large specific surface area, high mechanical strength, biocompatibility and low cost. In this review, the research status of modified nanocellulose for heavy metal adsorbents is primarily reviewed. Two primary forms of nanocellulose are cellulose nanocrystals (CNCs) and cellulose nanofibers (CNFs). The preparation process of nanocellulose was derived from natural plants, and the preparation process included noncellulosic constituent removal and extraction of nanocellulose. Focusing on heavy metal adsorption, the modification of nanocellulose was explored in depth, including direct modification methods, surface grafting modification methods based on free radical polymerization and physical activation. The adsorption principles of nanocellulose-based adsorbents when removing heavy metals are analyzed in detail. This review may further facilitate the application of the modified nanocellulose in the field of heavy metal removal.

Preparation of Ion2+-COS/SA Multifunctional Gel Films for Skin Wound Healing by an In Situ Spray Method

The rapid preparation of safe and efficient wound dressings that meet the needs of the entire repair process remains a major challenge for effective therapeutic wound healing. Natural, sprayable Ion²⁺-COS/SA multifunctional dual-network gel films created by the in situ coordination of chitooligosaccharide (COS), metal ions and sodium alginate (SA) using casting and an in-situ spray method were synthesized. The gel films exhibited excellent physicochemical properties such as swelling, porosity and plasticity at a COS mass fraction of 3%. Furthermore, at this mass fraction, the addition of bimetallic ions led to the display of multifunctional properties, including significant antioxidant, antibacterial and cytocompatibility properties. In addition, experiments in a total skin defect model showed that this multifunctional gel film accelerates wound healing and promotes skin regeneration. These results suggest that the sprayable Ion²⁺-COS/SA multifunctional pro-healing gel film may be a promising candidate for the clinical treatment of allodermic wounds.

Multifunctional Gel Films of Marine Polysaccharides Cross-Linked with Poly-Metal Ions for Wound Healing

The development of an efficient and convenient material to improve skin tissue regeneration is a major challenge in healthcare. Inspired by the theory of moist wound healing, portable chitooligosaccharide (COS)/sodium alginate (SA) dual-net gel films containing multiple metal ions were prepared by a casting and in-situ spray method, which can be used to significantly promote wound healing without the use of therapeutic drugs. A variety of divalent cations was introduced in this experiment to improve the advantages of each metal ion by forming metal ion chelates with COS. Moreover, the physicochemical properties and antioxidant properties of nIon²⁺-COS/SA gel films were systematically characterized and evaluated by in vitro experiments. The gel films showed good antibacterial activity against Gram-negative and Gram-positive bacteria. In addition, the gel films showed good cytocompatibility in cellular experiments, and the gel films with Zn²⁺ and Sr²⁺ addition significantly accelerated wound healing in whole skin defect model experiments. Therefore, this nIon²⁺-COS/SA gel film is an ideal candidate material for wound dressing.