Solidification and Stabilization of Spent Pine-cone Biochar using Chemically Bonded Phosphate Cement

Spent biochar is produced after adsorption of heavy metal which is hazardous by nature. A suitable disposal technique is required to prevent the leaching of heavy metals from spent biochar into the environment. This study highlights the solidification and stabilization (S/S) of copper loaded spent pine-cone biochar by chemically bonded phosphate cement (CBPC). The response surface methodology (RSM) was used to conduct S/S experiments in order to evaluate the compressive strength of CBPC products. The CBPC samples were prepared by varying biochar content (5-50 wt. %); W:S (0.15-0.3) and curing time(3-28d). Results illustrated that CBPC products containing biochar had higher compressive strength upto 12.8 MPa in comparison to CBPC without biochar i.e., upto 10.8 MPa. XRD and SEM analysis confirmed the presence of K-struvite (MgKPO4.6H2O), copper containing phases (Ca-Cu-Si), copper phosphate precipitates (Cu3(PO4)2) and filling of pore spaces by spent biochar. Highest compressive strength of 12.8 MPa was obtained at an optimized biochar content of 25%, W:S of 0.18 and curing time of 28 d. The evaluation of leaching potential by TCLP illustrated that stabilization of Cu (II) upto 99.9% was achieved in CBPC product. The risk assessment study revealed that there is no significant danger due to leaching of heavy metals from final CBPC product indicating that it can be readily disposed in the hazardous landfill sites

Investigation on laboratory and pilot-scale airlift sulfide oxidation reactor under varying sulfide loading rate

Airlift bioreactor was established for recovering sulfur from synthetic sulfide wastewater under controlled dissolved oxygen condition. The maximum recovered sulfur was 14.49 g/day when sulfide loading rate, dissolved oxygen (DO) and pH values were 2.97 kgHS-/m3-day, 0.2-1.0 mg/L and 7.2-7.8, respectively. On the other hand, the increase in recovered sulfur reduced the contact surface of sulfide oxidizing bacteria which affects the recovery process. This effect caused to reduce the conversion of sulfide to sulfur. More recovered sulfur was produced at high sulfide loading rate due to the change of metabolic pathway of sulfide-oxidizing bacteria which prevented the toxicity of sulfide in the culture. The maximum activity in this system was recorded to be about 3.28 kgS/kgVSS-day. The recovered sulfur contained organic compounds which were confirmed by the results from XRD and CHN analyzer. Afterwards, by annealing the recovered sulfur at 120°C for 24 hrs under ambient Argon, the percentage of carbon reduced from 4.44% to 0.30%. Furthermore, the percentage of nitrogen and hydrogen decreased from 0.79% and 0.48% to 0.00% and 0.14%, respectively. This result showed the success in increasing the purity of recovered sulfur by using the annealing technique. The pilot-scale biological sulfide oxidation process was carried out using real wastewater from Thai Rayon Industry in Thailand. The airlift reactor successfully removed sulfide more than 90% of the influent sulfide at DO concentration of less than 0.1 mg/L, whereas the elementary sulfur production was 2.37 kgS/m3-day at sulfide loading rate of 2.14 kgHS-/m3-day. The sulfur production was still increasing as the reactor had not yet reached its maximum sulfide loading rate

Reuse options for coal fired power plant bottom ash and fly ash

International audienc

Fluoride removal from groundwater using chemically modified rice husk and corn cob activated carbon

<p>The fluoride adsorption potential of chemically modified rice husk and corn cob activated carbon was investigated in batch and column tests. The effect of pH, contact time, initial fluoride concentration and adsorbent dose on the adsorption capacity and efficiency was studied. Batch experimental results were analysed using analysis of variance. The maximum adsorption capacity of 7.9 and 5.8 mg/g and a removal efficiency of 91% and 89% were achieved in batch tests, respectively, for rice husk and corn cob activated carbon. The adsorption data and kinetic model fitted well to the Langmuir isotherm and pseudo-second-order kinetics, respectively. Fluoride adsorption was governed by both intraparticle diffusion and surface or film diffusion for both rice husk and corn cob activated carbon. Continuous tests were carried out using three columns packed with 100% rice husk activated carbon, 100% corn cob activated carbon and 50% rice husk + 50% corn cob activated carbon. The breakthrough adsorption capacities were found to be 7.9, 5.0 and 5.2 mg/g, respectively. The results were analysed using the Thomas model, which yielded adsorption capacities of 11, 8.1 and 9.4 mg/g, respectively, for the three columns investigated.</p