Study On Controllable Construction Of High-Performance Functional Biochar And Its Application In Removing Arsenic From Drinking Water

Arsenic（As）contamination of surface and ground water is noticeable and worldwide issue because it causes serious health impacts on humans and animals.In many countries drinking water contains As at concentrations more than recommended by the world health organization(10 μg L^-1).A long term exposure to As causes so many serious health issues in humans such as skin cancer,kidney failure,lung,cardiovascular and neurological disorders.Therefore this study was conducted with the use of eco-friendly,inexpensive,and no conventional bio-waste materials for biochar instead of commercially available inorganic sorbents for the effective remediation of both inorganic species of As elimination from drinking/ground water along with their reusability potential through sorption/desorption cycles and results were compared with previously reported studies.The synthesis of biochar/nanoparticles-enabled hybrid sorbents can provide an environmentallysustainable and low-cost solution to remediate arsenic（As）-contaminated water affecting millions of people globally.Here,in the first two studies,we explored the potential of a newly prepared nano-zero valent zinc（nZVZn）,biochar（BC）/nZVZn and BC/hydroxyapatite-alginate（BC/HA-alginate）composites for removal of As（Ⅲ）and As（Ⅴ）from water separately.Relatively,higher percentage removal of As（Ⅲ）and As（Ⅴ）was obtained by nZVZn at pH 3.4（96% and 94%,respectively）compared to BC/nZVZn（90% and 88%）and BC/HA-alginate（88% and 80%）at pH 7.2.Freundlich model provided the best fit（R2 = up to 0.98）for As（Ⅲ）and As（Ⅴ）sorption data of all the sorbents,notably for nZVZn.The pseudo-second order model welldescribed kinetics of As（Ⅲ）and As（Ⅴ）（R2 = 0.99）sorption on all the sorbents.Interestingly,the desorption experiments demonstrated that the As removal efficiency,up to the third sorption/desorption cycle,was in the order of nZVZn BC/HA-alginate（88%）> BC/nZVZn（84%）.The XPS,SEM and XRD techniques were examined.The FTIR spectroscopy depicted that the –OH,–COOH,Zn–O and Zn–OH surface functional groups were responsible for the sorption of As（Ⅲ）or As（Ⅴ）on the sorbents investigated here.This study highlights that the removal of both inorganic As species from water by BC/nZVZn composite is almost comparable with nZVZn,suggesting that integrating BC with nZVZn is a chemical process that involves complex redox transformation and surface functional moieties in aquatic systems;can be a lowcost,eco-friendly and sustainable approach for the removal of As from drinking water.In the next study,we compared sugarcane bagasse biochar（SCB）,rice husk biochar（RH）thiolated-SCB（TH–SCB）,thiolated-RH（TH–RH）,for As（Ⅲ）removal from As-contaminated water.Sorption experiments were carried out as a function of pH,initial As concentration,sorbent dose and time,using thiolated and un-thiolated sorbents.Batch sorption studies data revealed maximum As（Ⅲ）removal at pH 7 by TH-SCB and TH-RH（92% and 83%）which is higher than un-thiolated SCB and RH（65% and 55%）and previous research.Langmuir model provided the best fit to describe As（Ⅲ）sorption by all the sorbents.The pseudo-second-order model well-described kinetics of As（Ⅲ）and As（Ⅴ）（R2 = 0.99）sorption on all the sorbents.All sorbents used in this study showed preferably up to third sorption/desorption as followed TH–SCB（88%）> TH–RH（82%）> SCB（77%）> RH（69%）.The XPS,SEM and XRD techniques were studied.Fourier transform infrared spectroscopy（FTIR）and X-ray photoelectron spectroscopy（XPS）analyses revealed that mainly the S–H,–OH,–COOH,and C=O surface functional groups were involved in As（Ⅲ）sorption by studied sorbents.The study highlights that modifications of SCB and RH with thiolation can substantially enhance their remediation potential,making thiolated sorbents more efficient in removing As（Ⅲ）from contaminated water.