Hazardous Pollutants Remediation Performance of Carbonaceous Materials from Forest Waste Conversion

Osvaldo Reggie^*
*Correspondence: Osvaldo Reggie, Department of Environmental Engineering, University of Holy Federal, Vitoria, Brazil, Email:

Introduction

The change of lignocellulose squander rises as a promising way to create new materials with wide modern and ecological purposes. For the purpose of removing lead from aqueous effluents, pyrolytic bio char (PBc), hydro char (Hc) and activated hydro char (AcHc) that were made from the waste of Picea abies bark were regarded as bio-based sorbents. Hc was produced through hydrothermal conversion, whereas PBc was produced through slow pyrolysis. AcHc was produced when Hc was subjected to a physical activation in order to enhance the specific surface. Using a readily available local resource, the relatively straightforward preparation of all three carbonaceous materials was accomplished. Scanning electron microscopy and infrared spectroscopy were used to analyse the carbonaceous materials. Both a real mine drainage effluent and a synthetic mono component wastewater matrix have been used to test the Pb removal in batch mode. The pH had a significant impact and the equilibrium was reached quickly about 60 minutes for PBc and Hc and 120 minutes for AcHc. A maximum adsorption capacity of 15.94 mg/g for PBc, 9.99 mg/g for Hc and 37.46 mg/g for AcHc was predicted by the Langmuir model. Lead was well absorbed by all of the studied materials without having a significant impact on typical coexisting species.

Description

It is assessed that 1 billion tons of lignocellulose biomass will be created in Europe by 2030, while 476 million tons address the prerequisite to finish the requirements of all bio based European businesses. As a by-product of forest processing, wood biomass is utilized as a feedstock for bioenergy processes, pulp and paper, the production of wood pellets, engineered wood products and as a raw material for bio products with added value. Chemical stability, very good conductivity, good porosity and surface area are all general characteristics of carbonaceous materials, as is their cost-effectiveness. Chars, fullerenes, carbon nanotubes, graphene or graphene-like particles and activated carbon are examples of such extremely adaptable materials. Carbonaceous materials are extensively used as electrode materials and play a crucial role in electrochemical energy storage and conversion devices. They are also utilized for the preparation of composites, catalysis and carbon sequestration. As effluent remediation sorbents, these carbon-rich materials also have numerous applications that are perfectly compatible with a sustainable and polluting strategy [1].

The solid phase that results from the pyrolysis of biomass is referred to as bio char and its characteristics are contingent not only on the parameters of the conversion process but also on the feedstock. With comparable sorption efficiency for various inorganic contaminants, it is regarded as a low-cost alternative to activated carbon. The estimated break-even price for bio char is US $246 per ton, or about one-sixth of the price of commercially available activated carbon, which is US $1500 per ton. This is because bio char is made cheaply from waste. The adsorption of toxic sludge onto bio chars appears to be a very encouraging approach in comparison to conventional technologies used for hazardous waste removal, which typically have secondary polluting effects due to the handling and disposal of toxic sludge. Through hydrothermal carbonization, a carbonaceous material known as hydro char is produced. Hydrothermal carbonization is caused by reactions like hydrolysis, dehydration, aromatization, decarboxylation and re-condensation. Since this method of conversion does not require a previous drying stage, it is less expensive than other methods, does not pollute the environment and is simple to perform. Activated carbon can be made from materials with a lot of carbon, like hydro and bio chars. Two strategies (physical and synthetic) are generally utilized for initiation. Activated carbon has a large and complex surface area in addition to its porous structure, which contributes to its excellent adsorption capacity [2].

The results of studies on batch-mode lead adsorption capacities, primarily for modified bio char, were promising, according to the literature. When bio char from pomelo peels was tested, it was found to have an adsorption capacity of 88.7 mg/g through the mechanism of precipitation of phosphorous functional groups after being dried, impregnated with H₃PO₄ and then pyrolyzed. After being washed, dried, milled, pyrolyzed and treated with hydrated manganese oxide, the peanut shell had a 36 mg/g adsorption capacity. Through a complexation mechanism involving oxygen functional groups, maple wood that had been dried, pyrolyzed and modified with H₂O₂ had a maximum adsorption capacity of 43.3 mg/g. Jimenez tested, dried and ground pecan shell, this bio char has a maximum adsorption capacity of 80.3 mg/g thanks to ion exchange mechanisms involving calcium ions. A critical analysis of bio chars utilized in wastewater treatment explains how feedstock is pre and post-treated to influence bio char production and the adsorption capacities of various bio chars for various contaminants.

Heavy metal uptake from contaminated effluents was also accomplished with hydro char, either as-is or enhanced by pre-treatments. The hydrothermal parameters and the feedstock used determine the adsorption capacity. The ability of a hydro char made from the hydrothermal carbonization of peanut hull to remove lead, likewise, it had a sorption capacity of 22.82 mg/g. After testing dithiocarbamate-modified hydro char made from agricultural and forestry waste, a significantly higher lead retention capacity (151.51 mg/g) was revealed. When compared to the unmodified hydro char, the pinewood sawdust hydro char with a 20% H₂O₂ solution has a significantly higher adsorption capacity of Pb2+ (92.80 mg/g). Initiated carbon is a notable adsorbent for weighty metals sequestration from wastewater, including lead. When activated carbon and metal oxides (Fe(OH)₃ and TiO₂) were used as sorbents to remove lead, their performance was compared and activated carbon had a lower adsorption capacity of 21.2 mg/g than metal oxides. The pine cone-derived activated carbon had a retention capacity of 27.53 mg/g. A winemaking waste-derived activated carbon, on the other hand, had a maximum adsorption capacity of 58 mg/g for a low initial lead solution concentration (only 10 mg/L Pb). In addition, the competitive adsorption behavior, the adsorbent's structure, the adsorption mechanism and the interaction between lead and functional groups of activated carbons were thoroughly investigated [3].

However, the majority of the earlier research that was cited used bio chars, hydro chars, or activated carbons that had been improved through a variety of chemical processes. The studies also took into account high initial concentrations of lead, which, most of the time, were higher than the concentration of lead that was reported for wastewater streams. Lead contamination of the natural environment (water, soil and air) could go above the allowed limits and put the health or even life of living things in danger, either from endogenous or anthropogenic sources. Lead contributes significantly to the contamination of water streams due to the manufacturing of pesticides, paints, pigments, glass, chemicals, electroplating industries, metal mining and lead-acid batteries, all of which have concentrations in wastewater or much higher. As a result, there have been reports of toxic effects on humans, depending on the dose and duration of exposure. Lead and its inorganic compounds are likely to be human carcinogens, according to the International Agency for Research on Cancer (IARC). In contrast, lead and inorganic lead compounds are categorized as confirmed animal carcinogens by the American Conference of Governmental Industrial Hygienists (ACGIH). Lead's toxic effects on the central nervous system are more pronounced in children than in adults, who develop peripheral neuropathy and hypertension [4,5].

Conclusion

As a result, removing lead from contaminated environments, particularly wastewater, remains a crucial objective and a public health and environmental emergency. In this study, three distinct kinds of carbonaceous materials were investigated using a variety of conversion methods on spruce bark waste: biochar (PBc), hydrochar (Hc) and actuated hydrochar (AcHc). A critical comparative study on the lead uptake capacity of these biobased carbonrich materials and a possible mechanism of lead sequestration in correlation with the chemical and structural characteristics of the sorbents are provided by this work, as well as a chemical and structural characterization of these carbon materials. Both a real mine drainage effluent stream and a monocomponent wastewater matrix were used in the study. In addition, the initial concentration of the lead solution is deliberately adjusted to take into account the concentrations that have been observed in industrial wastewater pollution. Given that concentrations are difficult to remove from real complex effluent matrixes, no other studies have reported the use of PBc, Hc and AcHc from spruce bark in aqueous lead remediation.

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