Characterization of Biochars Produced by Co-Pyrolysis of Hami Melon (Cantaloupes) Straw Mixed with Polypropylene and Their Adsorption Properties of Cadmium

Characterization and Adsorption Capacity of Modified Biochar for Sulfamethylimidine and Methylene Blue in Water

In this study, a composite of pond mud and lanthanum- and nano-zero valent iron-modified-biochar was investigated for its ability to adsorb methylene blue (MB) and sulfamethazine (SMZ). La-modified attapulgite and nano-zero valent iron (surface area enhanced by 43.7% via Brunauer-Emmett-Teller analysis) were successfully loaded onto the straw-sediment biochar (BC) surface. With the increase in pyrolysis temperature, the biocompatibility yield, the H, O, and N content, and the ratio of carbon elements decreased, while the pH value, surficial micropores, C element, and ash content increased. The biocarbon small molecules were gradually and tightly ordered, and the organic groups such as hydroxyl, carboxyl groups, and carbon oxygen double bonds were gradually lost or disappeared. The original Fe-BC had more phenolic hydroxyl groups forming an intermolecular hydrogen bond than others with a higher adsorption capacity possibly through the Schiff base reaction. The effect of various pH (2-9), temperature (15-35 °C), and initial concentration (1-25 mg L-1) on adsorption was investigated. pH and temperature were the main factors governing the adsorption process. The maximum adsorption capacity was observed at pH 4. The adsorption performances for MB followed the order Fe-BC > La-BC > BC, and the maximum removal rate was over 98.45% with pH = 7. The three types of BC dosages between 0.2 (6.67 g L-1) and 0.4 g showed a removal rate of 99% for MB. The adsorption capacity of Fe-BC, La-BC, and BC for MB was 2.201, 1.905, and 2.401 mg L-1 with pH = 4, while 4.79, 4.58, and 5.55 mg g-1 were observed with BC dosage at 0.025 g. For SMZ, the higher the temperature, the better the adsorption effect, and it reaches saturation at approximately 25 °C. To further evaluate the nature of adsorption, Langmuir/Freundlich/Temkin models were tested and the adsorption capacities were evaluated on the surface of the BC composite. The three modified materials were physisorbed to SMZ, while MB was chemisorbed. For MB, the adsorption performance of BC is the best < 0.2 g (6.67 g L-1) at pH 7.0 at 35 °C. The Elovich model was more suitable for MB, while the Freundlich and Temkin models could better fit the adsorption process of MB. The preparatory secondary dynamics equation and Langmuir equation were more compliant for SMZ, and the saturated adsorption capacities of straw-modified, La-BC, and Fe-BC reached 5.699, 6.088, and 5.678 mg L-1, respectively.

Fabrication of biochar-based superhydrophobic coating on steel substrate and its UV resistance, anti-scaling, and corrosion resistance performance

In this study, we report an eco-friendly and facile process for the synthesis of biochar, BC, and a cobalt-biochar nanocomposite, Co-BC, using rice straw biomass. We constructed two superhydrophobic coatings on steel substrates using potentiostatic electrodeposition of nickel-modified biochar, Ni@BC, and nickel modified by cobalt-biochar nanocomposite, Ni@Co-BC, then, these coatings were soaked in an ethanolic stearic acid solution. Fourier transform infrared spectroscopy showed that the stearic acid-grafted Ni@BC coating, Ni@BC@SA, and the stearic acid-grafted Ni@Co-BC composite, Ni@Co-BC@SA, were well grafted on the steel surface. Scanning electron microscopy revealed that the superhydrophobic coatings have nanoscale features. Atomic force microscopy results showed that the Ni@Co-BC@SA coat had higher roughness than Ni@BC@SA, resulting in higher superhydrophobicity. The water contact angles for Ni@BC@SA and Ni@Co-BC@SA coatings were 161° and 165°, respectively, while the values of water sliding angles for both coatings were 3.0° and 1.0°, respectively. Quantitative estimation of the scale inhibition efficiency revealed that the Ni@Co-BC@SA coating exhibited greater efficiency compared to the Ni@BC@SA coating. Additionally, the Ni@Co-BC@SA coating demonstrated improved corrosion resistance, UV resistance, mechanical abrasion resistance, and chemical stability compared to the Ni@BC@SA coating. These results highlight the superior performance of the Ni@Co-BC@SA coating and its potential as a highly effective and durable superhydrophobic coating for steel substrates.

Investigation of gauze and medical bottle co-pyrolysis on the product formation, reactivity, and reaction pathway of char, liquid oil, and gas

Effective in-site treatment of medical waste has become a weak link in hospitals. Pyrolysis technology is a treatment method for medical waste that can enable rapid disposal in hospital settings and relieve environmental pressure, while also producing high-value products and reducing disposal costs. In this work, the effects of feedstock ratio and temperature on product yield and components of gauze (GA) and medical bottles (MB) co-pyrolysis have been investigated. The higher yield of solid products was obtained by co-pyrolysis of GA and MB at 400 ℃. With the addition of MB and an increase in temperature for the co-pyrolysis of GA and MB in a similar ratio, the pyrolysis oil and gas yields gradually increased. According to GC-MS analysis, co-feeding 75% MB to GA improved the alcohol content from 33.21% to a maximum yield of 59.8% at a pyrolysis temperature of 700 ℃. The content of aliphatic hydrocarbon reached 38.68% when the pyrolysis temperature and MB addition ratio were 700 °C and 75%, respectively. The GC data shows that the main gas components of co-pyrolysis of GA/MB were CH4 and H2, while the pyrolysis of pure GA or MB resulted in CO or CO2. Additionally, the solid carbon products obtained have an excellent pore structure. This strategy can benefit medical waste control and resource utilization for the low-cost disposal of medical waste and the acquisition of high-value resource products.

Graphical Abstract

Fixed-Bed Column Adsorption Studies: Comparison of Alginate-Based Adsorbents for La(III) Ions Recovery

The paper investigated the adsorption of the packed-bed column with the alginate-based adsorbents (ALG-based adsorbents) such as alginate-biochar, alginate-clinoptilolite, alginate-lignin, and alginate-cellulose for La(III) ions' removal. Fixed-bed adsorption studies with various alginate-based adsorbents were carried out and compared to the La(III) ions adsorption. The columns were filled with ALG-based adsorbent beads of approximately 1.1 ± 0.005 mm spherical shapes. The effects of the inlet concentrations on the breakthrough curves were studied in terms of the adsorption performance of the ALG-based adsorbents. The experimental data were correlated with the Adams-Bohart, Yoon-Nelson, Thomas, and Wolborska models to determine the best operational parameters. Based on the comparison of R² values, the Thomas and Yoon-Nelson models were found to be more suitable than the Adams-Bohart and Wolborska models. In the desorption study, the ALG-based adsorbents packed columns showed the maximum desorption of La(III) just after passing 100 cm³ of 1 mol/dm³ HCl. Overall, the results show that ALG-based adsorbents could be used for continuous recovery of La(III) ions from aqueous solutions and were not only cost-effective but also environmentally friendly.

Construction of superhydrophobic graphene-based coating on steel substrate and its ultraviolet durability and corrosion resistance properties

For the first time, a facile and environmentally friendly approach for producing high-quality graphene from the biomass of banana leaves is described in this paper. Two rough coats of Ni-graphene, Ni@G, and Ni-graphene doped with chromium, Ni@Cr-G, were created on steel substrates by electrostatic deposition. These coatings were then submerged in an ethanolic solution of myristic acid, MA, to produce a superhydrophobic, SHP, surface. The Raman spectra demonstrated that the generated graphene was of high quality. Fourier transform infrared spectroscopy findings confirm the modification of the Ni@G coating by MA, Ni@G@MA, and the modification of the Ni@Cr-G composite with MA, Ni@Cr-G@MA. The results of the scanning electron microscope revealed that the created SHP coatings have nanoscale features. The wettability results showed that the water contact angle values for Ni@G@MA and Ni@Cr-G@MA coatings are 158° and 168°, while the water sliding angle values for both coatings are 4.0 ^o and 1.0°, respectively. The atomic force microscopy results show that both Ni@G and Ni@Cr-G coatings increase the roughness of the steel. The chemical and mechanical stability of the Ni@Cr-G@MA coating was higher than those of the Ni@G@MA coating. The coated steel by Ni@Cr-G@MA exhibits UV stability up to 110 h, while the SHP-coated steel by Ni@G@MA exhibits UV stability for 60 h. The potentiodynamic polarization results show that the value of the corrosion current density for bare steel is 13 times that of steel coated with Ni@G@MA, and 21 times that of coated steel with Ni@Cr-G@MA. The electrochemical impedance spectroscopy, EIS, results show that the charge transfer resistance for steel coated with Ni@G@MA is 38 times that of bare steel, while steel coated with Ni@Cr-G@MA is 57 times that of bare steel. Potentiodynamic polarization and EIS results show that the SHP Ni@Cr-G@MA film exhibits higher corrosion resistance than Ni@G@MA film.

A review of prospects and current scenarios of biomass co-pyrolysis for water treatment

With ever-growing population comes an increase in waste and wastewater generated. There is ongoing research to not only reduce the waste but also to increase its value commercially. One method is pyrolysis, a process that converts wastes, at temperatures usually above 300 °C in a pyrolysis unit, to carbon-rich biochars among with other useful products. These chars are known to be beneficial as they can be used for water treatment applications; certain studies also reveal improvements in the biochar quality especially on the surface area and pore volume by imparting thermal and chemical activation methods, which eventually improves the uptake of pollutants during the removal of inorganic and organic contaminants in water. Research based on single waste valorisation into biochar applications for water treatment has been extended and applied to the pyrolysis of two or more feedstocks, termed co-pyrolysis, and its implementation for water treatment. The co-pyrolysis research mainly covers activation, applications, predictive calculations, and modelling studies, including isotherm, kinetic, and thermodynamic adsorption analyses. This paper focuses on the copyrolysis biochar production studies for activated adsorbents, adsorption mechanisms, pollutant removal capacities, regeneration, and real water treatment studies to understand the implementation of these co-pyrolyzed chars in water treatment applications. Finally, some prospects to identify the future progress and opportunities in this area of research are also described. This review provides a way to manage solid waste in a sustainable manner, while developing materials that can be utilized for water treatment, providing a double target approach to pollution management.

Adsorption Performance of Cd(II) by Chitosan-Fe3O4-Modified Fish Bone Char

In order to develop a low-cost, fast, and efficient adsorbent, the fish bone charcoal B₆₀₀ prepared at 600 °C was modified by chitosan (Cs) and Fe₃O₄ to produce the material Cs-Fe₃O₄-B₆₀₀. Results showed that Cs-Fe₃O₄-B₆₀₀ had magnetic responsiveness and can achieve solid–liquid separation, macropores disappeared, pore volume and specific surface area are increased, and amino functional groups appear on the surface. The adsorption process of Cd(II) by Cs-Fe₃O₄-B₆₀₀ conformed best to the pseudo-second order kinetics model and the Langmuir model, respectively. The behavior over a whole range of adsorption was consistent with chemical adsorption being the rate-controlling step, which is a very fast adsorption process, and the isothermal adsorption is mainly monolayer adsorption, which belongs to favorable adsorption. In addition, the saturated adsorption capacity obtained for the Cs-Fe₃O₄-B₆₀₀ to Cd(II) was 64.31 mg·g⁻¹, which was 1.7 times than B₆₀₀. The structure and morphology of Cs-Fe₃O₄-B₆₀₀ were characterized through SEM-EDS, TEM, FTIR, and XRD, indicating that the main mechanism of Cs-Fe₃O₄-B₆₀₀ and Cd(II) is mainly the complexation of amino groups, and it also includes part of the ion exchange between Cd(II) and Fe₃O₄. Therefore, Cs-Fe₃O₄-B₆₀₀ can be employed as an effective agent for remediation of Cd contaminated water.