Effects of Biochar Production Methods and Biomass Types on Lead Removal from Aqueous Solution

Application of machine learning in prediction of Pb2+ adsorption of biochar prepared by tube furnace and fluidized bed

Data mining by machine learning (ML) has recently come into application in heavy metals purification from wastewater, especially in exploring lead removal by biochar that prepared using tube furnace (TF-C) and fluidized bed (FB-C) pyrolysis methods. In this study, six ML models including Random Forest Regression (RFR), Gradient Boosting Regression (GBR), Support Vector Regression (SVR), Kernel Ridge Regression (KRR), Extreme Gradient Boosting (XGB), and Light Gradient Boosting Machine (LGBM) were employed to predict lead adsorption based on a dataset of 1012 adsorption experiments, comprising 422 TF-C groups from our experiments and 590 FB-C groups from literatures. The XGB model showed superior accuracy and predictive performance for adsorption, achieving R2 values for TF-C (0.992) and FB-C (0.981), respectively. Contrasting inferior results were observed in other models, including RF (0.962 and 0.961), GBR (0.987 and 0.975), SVR (0.839 and 0.763), KRR (0.817 and 0.881), and LGBM (0.975 and 0.868). Additionally, a hybrid dataset combining both biochars in Pb adsorption also indicated high accuracy (0.972) as obtained from XGB model. The investigation revealed that the influence of char characteristics and adsorption conditions on Pb adsorption differs between the two biochar. Specific char characteristics, particularly nitrogen content, significantly influence lead adsorption in both biochar. Interestingly, the influence of pyrolysis temperature (PT) on lead adsorption is found to be greater for TF-C than for FB-C. Consequently, careful consideration of PT is crucial when preparing TF-C biochar. These findings offer practical guidance for optimizing biochar preparation conditions during heavy metal removal from wastewater.

Agrowaste-generated biochar for the sustainable remediation of refractory pollutants

The rapid growth of various industries has led to a significant, alarming increase in recalcitrant pollutants in the environment. Hazardous dyes, heavy metals, pesticides, pharmaceutical products, and other associated polycyclic aromatic hydrocarbons (such as acenaphthene, fluorene, fluoranthene, phenanthrene, and pyrene) have posed a significant threat to the surroundings due to their refractory nature. Although activated carbon has been reported to be an adsorbent for removing contaminants from wastewater, it has its limitations. Hence, this review provides an elaborate account of converting agricultural waste into biochar with nanotextured surfaces that can serve as low-cost adsorbents with promising pollutant-removing properties. A detailed mechanism rationalized that this strategy involves the conversion of agrowaste to promising adsorbents that can be reduced, reused, and recycled. The potential of biowaste-derived biochar can be exploited for developing biofuel for renewable energy and also for improving soil fertility. This strategy can provide a solution to control greenhouse gas emissions by preventing the open burning of agricultural residues in fields. Furthermore, this serves a dual purpose for environmental remediation as well as effective management of agricultural waste rich in both organic and inorganic components that are generated during various agricultural operations. In this manner, this review provides recent advances in the use of agrowaste-generated biochar for cleaning the environment.

Production of Activated Carbon from Sifted Coke and Determination of Its Physicochemical Characteristics

The possibility of obtaining effective coal sorbents from a low-liquid product of coke chemical production-coke fines-has been studied. To obtain a coal sorbent, coke fines with a size of ≤10 mm were crushed and sieved to obtain a fraction of 2-5 mm. The resulting fraction was activated in a specially designed reactor at 850 °C with steam treatment. Activation was carried out at different durations of the process: 60, 90, and 120 min. It was found that the sample obtained with a process duration of 120 min has the best indicator for the ability to remove phenol from aqueous solutions (74.94 mg/g) and methylene blue (145 mg/g). When cleaning tap water with the resulting carbon sorbent, there is a decrease in the content of calcium, sulfates, and bicarbonate and a decrease in total mineralization. Obtained activated carbon was studied by scanning electron microscopy, low-temperature nitrogen adsorption (BET), and FTIR spectroscopy. It was found that the resulting activated carbon has a porous structure consisting of meso- and macropores, and the specific surface value was ~301 m2/g. The presence of high-intensity absorption bands corresponding to acid functional groups has also been established.

Chicken Cartilage-Derived Carbon for Efficient Xylene Removal

Chicken cartilage was used for the first time as a raw material for the microwave-assisted synthesis of biochar and activated carbon. Various microwave absorbers, i.e., commercial active carbon, scrap tyres, silicon carbide, and chicken bone-derived biochar, as well as various microwave powers, were tested for their effect on the rate of pyrolysis and the type of products formed. Biochars synthesised under 400 W in the presence of scrap tyres and chicken bone-derived biochar were activated with KOH and K₂CO₃ with detergent to produce activated carbon with a highly developed porous structure that would be able to effectively adsorb xylene vapours. All carbons were thoroughly characterised (infrared spectroscopy, X-ray fluorescence spectrometry, nitrogen adsorption/desorption, Raman spectroscopy, proximate and ultimate analysis) and tested as xylene sorbents in dynamic systems. It was found that the activation causes an increase of up to 1042 m²·g^-1 in the specific surface area, which ensures the sorption capacity of xylene about 300 mg·g^-1. Studies of the composition of biogas emitted during pyrolysis revealed that particularly valuable gaseous products are formed when pyrolysis is carried out in the presence of silicon carbide as a microwave absorber.