Adsorption of Methylene Blue by Low-Cost Biochar Derived from Elephant Dung

Elephant dung biochar (ED350) prepared by controlled heating at 350 ºC was used to adsorb methylene blue (MB) in an aqueous solution. The effects of adsorption time, pH, adsorbent dosage, and initial MB concentration were examined. Kinetic, isotherm, and thermo-dynamic models were then further analyzed to determine the adsorption. The results show that ED350 was found to be efficient within 180 min. The optimum pH of MB adsorption was 11. The Langmuir isotherm model was found to be the most suitable fit for the adsorption equilibrium data, with ED350 having a homogeneous surface. The calculated equilibrium parameter (RL) values were greater than zero and less than one, indicating a favorable adsorption process and that ED350 was an efficient adsorbent for MB removal. The kinetics of MB adsorption onto ED350 obeys the pseudo-second-order model. The results of thermo-dynamic data consideration reveal that the adsorption process is spontaneous and exothermic in nature. This finding suggests that ED350 may prove to be an efficient low-cost adsorbent of MB from wastewater

Analysis of microbial fuel cell operation in acidic conditions using the flocculating agent ferric chloride

© 2014 Society of Chemical Industry. BACKGROUND: Ferric chloride (FeCl3) is widely used as a flocculating agent during wastewater treatment but can detrimentally lower pH and increase iron concentration. Microbial fuel cells (MFCs) are a promising technology for treating waste while concomitantly producing electricity and so were tested under the extreme conditions imposed by the addition of FeCl3. MFCs were fed eight concentrations of FeCl3 over two 8-week periods and the effects on power, pH, conductivity, metal content and COD were examined. RESULTS: MFCs generated highest power (3.58Wm-3) at 1.6mmolL-1 FeCl3 (pH 3.46), however cells reversed when fed 2mmolL-1 (pH 3.29). During the second run, power almost doubled and MFCs were more resilient at higher loadings up to 2.8mmolL-1 (pH 3.02). Conductivity and pH increased following treatment while soluble phosphorus, sulphur and iron levels decreased significantly in all feedstock up to 1.6mmolL-1 FeCl3. COD reduction was observed but efficiency may have been affected by the presence of alternative electron donors such as hydrogen sulphide. CONCLUSION: These findings demonstrate the robustness and versatility of MFCs in hostile conditions. They also confirm that MFCs can complement current wastewater treatment processes, even downstream from FeCl3 dosing where conditions might be deemed unsuitable for operation

Mechanistic and phenotypic studies of bicarinalin, BP100 and colistin action on Acinetobacter baumannii

Acinetobacter baumannii has been identified by the WHO as a high priority pathogen. It can be resistant to multiple antibiotics and colistin sulphate is often used as a last-resort treatment. However, the potentially severe side-effects of colistin are well documented and this study compared the bactericidal and anti-biofilm activity of two synthetic nature-inspired antimicrobial peptides, bicarinalin and BP100, with colistin. The minimum bactericidal concentration (MBC) against planktonic A. baumannii was approximately 0.5 μg/ml for colistin sulphate and ∼4 μg/ml for bicarinalin and BP100. A. baumannii commonly occurs as a biofilm and biofilm removal assay results highlighted that both bicarinalin and BP100 had significantly greater potential than colistin. Atomic force microscopy (AFM) showed dramatic changes in A. baumannii cell size and surface conformity when treated with peptide concentrations at and above the MBC. Scanning electron microscopy (SEM) visualised the reduction of biofilm coverage and cell surface changes as peptide concentration increased. Liposome assays revealed that these peptides most likely act as pore-forming agents in the membrane. Bicarinalin and BP100 may be effective therapeutic alternatives to colistin against A. baumannii infections but further research is required to assess if they elicit cytotoxicity issues in patients