Nutrient pollution poses a significant global environmental threat, and addressing this issue remains an ongoing challenge. Biochar has been identified as a potential adsorbent for environmental remediation. However, raw biochar has a low nitrate adsorption capacity; thus, biochar modification is necessary for targeted environmental applications. This work explored and compared the performance of Fe-doped, N-doped, and N-Fe-co-doped biochars from Douglas fir toward nitrate removal from an aqueous solution. A central composite experimental design was used to optimize processing variables, maximizing the surface area and nitrate adsorption capacity. Proximate analysis, elemental composition, gas physisorption, XPS, SEM, TEM, FTIR, and XRD were used to characterize the biochar’s properties. Pyrolysis under NH₃ gas generated more pores in biochar than conventional pyrolysis. Doping biochar with N and Fe improved nitrate adsorption capacity from aqueous solutions. The maximum nitrate adsorption capacity of Fe-N-doped biochar produced at 800 °C was 20.67 mg g⁻¹ in sorption tests at pH 3.0. The formation of N-containing functional groups and Fe oxides on the biochar surface enhanced the nitrate removal efficiency of N-Fe biochar. The results indicate that biochar’s adsorption capacity for NO₃⁻ is largely affected by the solution’s pH and biochar’s surface chemistry. Electrostatic attraction is the primary mechanism for nitrate adsorption.

Wet oxidation can be an effective process for the pretreatment of complex biomass such as lignocellulose. However, studies on the use of wet oxidation for treating solid waste such as dairy manure are limited. The use of partial wet oxidation to convert dairy manure into low molecular weight carboxylic acids as final products were investigated. This work focuses on the performance of the sub-critical wet oxidation treatment of dairy cattle manure as a conversion/pretreatment process to release matter from the lignocellulosic fraction rather than a destructive process. The operating conditions were controlled at the short residence time and optimal temperature in the presence of oxygen under a pressure of 120 psi. The thermal hydrolysis under wet oxidation significantly affected conversion manure slurry into organic acids. The concentration of acetic acid reached 1778 mg L⁻¹, achieved at 190°C (60 minutes reaction time) as the reaction temperature increased within the range of 150°C–200°C, total organic carbon was reduced and monomers in the process liquids decreased. On the other hand, soluble COD in process liquids increased with an increment in reaction temperature. The results provide insights into technical options to pretreat dairy manure to improve biochemical conversion yield.

Background: Access to safe drinking water remains a global issue with fecal indicator bacteria being major pollutants. Biochars offer low-cost adsorbents for bacterial pathogens. A fundamental understanding of how biochars interact with bacterial pathogens is essential to designing effective biofilters. Methods: Water-saturated sand columns amended with Magnesium and Nitrogen-doped biochars produced by pyrolysis at 400, 500, 600, and 700 °C were used to Quantify the transport of pathogenic Escherichia coli O157:H7 and nonpathogenic E. coli k12 strains in porous media. Measured data were modeled using DLVO theory of colloidal stability. were explored. Results: (1) Biochar is hydrophobic while sand and bacteria are hydrophilic; (2) all Gibbs free energy values quantified between E. coli O157:H7 and biochar were negative except for biochar produced at 700 °C; (3) all types of forces investigated (van der Waals, electrostatic, and acid-base interactions) played a role in governing the interactions between bacteria and biochar. Conclusions: (1) Adding doped biochar to sand at a 2% weight ratio enhanced the retention of bacterial cells in the sand/biochar columns; (2) bacterial transport is strain-dependent and mediated by various types of forces resulting from interactions between the various functional groups displayed on bacteria and biochar/sand. Our findings emphasize the importance of monitoring biochar’s functionality to eliminate bacterial pollutants from contaminated water.

The use of biochar for different applications has received much attention over the past years due to its unique properties, such as desired surface area, porous structure, and surface functional groups. There are many factors affecting the properties of biochar. By selecting appropriate feedstock, carbonization (i.e., equipment, processing temperature, heating rate, and residence time), and post-carbonization or activation conditions (e.g., physical activation, chemical activation, and biological modification), it is possible to control biochar micro- and nano-properties. This chapter aims to describe the connection between feedstock composition, carbonization conditions, and biochar structure at the micro- and nano-level scale. The link between these structures and adsorption, reaction, and electrochemical phenomena relevant to the use of biochar for environmental remediation are discussed. <!----> <!----> <!----> <!---->