Characterizations and fluoride adsorption performance of wattle humus biosorbent.

Considering the serious health effects of fluoride contamination, an environment friendly bioadsorbent was derived from wattle humus for fluoride removal by conventional thermal activation process. Analytical characterizations revealed that heterogeneous morphological textured wattle humus enabled remarkable adsorption capacity. XPS analysis substantiated that fluoride had been successfully adsorbed on to the carbonized wattle humus surface through chemisorption. Fluoride adsorption efficiency was systematically rationalized via batch adsorption studies. Experiments were performed at different initial fluoride concentration and scrutinized the impact of contact time (10-120 min), adsorbent dosage (0.5-2.5 g), pH (2.0-9.0), and interfering co-existing ions (SO42-, NO3-, Cl-, and HCO3-) on fluoride removal. Even at different adsorbate dosage (2-10 mg/L), 98% fluoride removal efficiency was achieved under pH > 6. The competitive anions do not interfere the wattle humus fluoride adsorption capacity. Moreover, the adsorption isotherms and kinetics studies inferred that monolayer and multilayer adsorption behavior by wattle humus leads to noticeable fluoride adsorption. Adsorbent regeneration test affirms that regenerated adsorbent found higher (>95%) fluoride removal efficiency even at five recycle runs.

Electrocoagulants Characteristics and Application of Electrocoagulation for Micropollutant Removal and Transformation Mechanism.

Predominantly, the removal of dissolved contaminates via the Fe electrocoagulation (EC) process depends on the electrocoagulants stability, specific area, porosity, dissolution rate, and phase transformation kinetics. The present investigation elucidates the role of applied currents and electrolyte counteranions on the crystalline phase and surface topography of electrocoagulants generated from Fe EC. Moreover, the dissolved contaminant micropollutant removal efficiency was also evaluated by electrochemically produced coagulants. This study confirms that mixed-phase iron (oxyhydr) oxide nanostructures were consistently produced from Fe EC with predominant formation of the goethite phase. The applied current controls the morphology of the coagulants, with flake-like morphology observed with currents at and below 100 mA and spherical morphology observed with currents above 100 mA. The counteranions in the electrolyte also impacted the morphology with spherical, nanosheet, and nanorod morphologies produced by Cl- or SO42-, CO32-, and HCO3- counteranions, respectively. BET analysis revealed the formation of electrocoagulants with micro-, meso-, and macropores. Surface area was markedly reduced from 142.85 to 41.96 m2 g-1 by incident coagulation resulting from increased anodic dissolution. Applicability of the electrocoagulant was examined by different micropollutants (acetaminophen (AC), antipyrine (AT), and atenolol (AT)). Results suggest that >90% and >80% TOC reduction were achieved with Na2CO3 and NaHCO3 as electrolyte media. The lower TOC reduction was rationalized by the identified intermediate products, and possible micropollutant degradation pathways were proposed based on LC-MS/MS analysis.

Critical evaluation of mechanism responsible for biomass abatement during electrochemical coagulation (EC) process: A critical review.

This is a first review paper that delineates fundamental disinfection mechanism undergoes during the simple electrochemical coagulation (EC) process. The elucidation of detailed mechanistic phenomenon of EC process involved would help to enhance the disinfection efficiency. In this context, the biomass (bacteria, virus and algae) abatement mechanism by EC is critically reviewed and rationalized based on the experimental demonstration performed from the recent decade. Whereas, the effect of most significant abiotic operating parameters, dissolved contents and bacteria cell wall composition on biomass reduction are explored in detail. From these analyses, physical removal and chemical inactivation routes are identified for bacteria abatement mechanism during the EC process using sacrificial electrodes. Which includes (i) enmeshment of microbial contaminants by EC flocs, (ii) sweeping flocculation is preferentially for destabilization of negatively charged biomass, and (iii) inactivation/attenuation of micro-organism cell walls by electrochemically induced reactive oxygen species (ROS) or direct interaction of electric field. Perhaps, the overall abatement mechanism attributes due to the aforementioned phenomenon endures independently and/or synergistically during the EC process. Nonetheless, to obtain better understanding of virus and algae abatement mechanism, we require more experimental investigation on algae and virus removal. Eventually, more intensive research efforts on biomass attenuation by EC are most important to reinforce this claim.