# Effects of Biochar Production Methods and Biomass Types on Lead Removal from Aqueous Solution
## 3 Results and Discussion
### Biochar Yield and Properties
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Tube Furnace**} & \multicolumn{4}{c}{**BioCharlie Log**} \\ \hline \multirow{3}{*}{**Properties**} & **Avocado Seed** & **Avocado** & **Grapreruit** & **Brown** & **Avocado Seed** & **Avocado Seed** & **Grapreruit** & **Brown** \\  & **(AST)**2  & **Feel** & **Seaweed** & **(ASH)**2  & **Avocado Seed** & **Feel** & **Seaweed** \\  & **(APT)** & **(APT)** & **(APT)** & **(BST)** & **(APT)** & **(APB)** & **(GPB)** & **(BSB)** \\ \hline Yield (\%) & 42.50 & 56.18 & 47.57 & 63.15 & 36.65 & 48.65 & 41.72 & 51.12 \\ pH & 7.66 & 9.40 & 9.04 & 7.94 & 8.85 & 9.65 & 8.30 & 6.88 \\ EC (μs/cm) 1 & 125 & 272 & 855 & 1534 & 4466 & 3330 & 2400 & 2057 \\ Moisture (\%) & 1.67 & 3.46 & 1.02 & N/A & 3.67 & 5.45 & 1.15 & 0.86 \\ Volatile Matter (\%) & 28.17 & 23.85 & 30.00 & N/A & 33.87 & 58.71 & 35.52 & 8.27 \\ Ash Content (\%) & 34.38 & 28.81 & 23.10 & N/A & 17.57 & 6.25 & 17.33 & 68.06 \\ Fixed Matter (\%) & 35.78 & 43.88 & 45.88 & N/A & 44.89 & 29.59 & 46.00 & 22.81 \\ C (\%) & 60.33 & 54.21 & 53.50 & 27.87 & N/A & N/A & N/A & N/A \\ N (\%) & 1.38 & 1.02 & 1.59 & 1.6 & N/A & N/A & N/A & N/A \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Selected properties of biochar materials. from 6.89-8.29, which were comparable to the AST, BST, BSB, and GPB in the current study [22; 27; 28; 29]. EC for tube-furnace-produced biochars was 125-1534 us cm\({}^{-1}\) and that for BioCharlie-produced biochars was 2057-4466 us cm\({}^{-1}\) (Table 1). For the same biomass, BioCharlie-produced biochars showed consistently higher EC than tube-furnace-produced biochars. It was notable that ASB and APB (BioCharlie) showed 12-36 times greater EC than AST and APT (tube furnace), indicating that the pyrolysis temperature condition was likely to affect the difference. Biochars produced under higher pyrolysis temperatures generally have higher EC values, which is often attributed to higher concentrations of residues or ash [26; 27]. Brown seaweed biochars showed relatively high EC in both production methods (>1500 us cm\({}^{-1}\)). EC values in the current study were comparable to those (150-6000 us cm\({}^{-1}\)) from eight different biochars pyrolyzed at 300 \({}^{\circ}\)C [22]. With the exclusion of the BST biochar, BioCharlie-produced biochars showed higher volatile matter but less ash content than tube-furnace-produced biochars (Table 1). It was notable that BST biochar had a 68% ash content, reflecting the nature of marine biomass with the lowest volatile matter (8%). The fixed matter of biochar as a proxy for recalcitrant matter ranged from 23 to 46%. Grapefruit peel biochars showed the highest fixed matter (46%) in both production methods. Previous studies reported that the volatile matter ranged between 37 and 66%, the fixed matter ranged between 20 and 66%, and ash content ranged between 2 and 20% for similar biochars produced at 300 \({}^{\circ}\)C [21; 22; 23; 25; 30]. The C and N contents were examined for the tube-furnace-produced biochars only (due to the sample loss for BioCharlie-produced biochar), where the carbon content was 28-60% by weight, with AST being the highest carbon percentage (60%) and BST being the lowest (28%). The higher C content in AST and APT indicates a higher stability of C (i.e., a higher proportion of aromatic C and condensed aromatic structures) [31]. However, the C contents of AST and APT were lower than other land-based biochars (66-69%) from hickory wood, bagasse, and bamboo biochars pyrolyzed at 300 \({}^{\circ}\)C [28]. The C content of brown seaweed biochar in this study (28%) was in a similar range to a previous study that used cultivated seaweed as a biochar feedstock material (29%), reflecting its low C content in the original feedstock [32]. The N content was less than 2% by weight, which was a typical range for non-mannure-derived biochars [27].