Biochar-based composites for removing chlorinated organic pollutants: Applications, mechanisms, and perspectives

Chlorinated organic pollutants constitute a significant category of persistent organic pollutants due to their widespread presence in the environment,which is primarily attributed to the expansion of agricultural and industrial activities.These pollutants are characterized by their persistence,potent toxicity,and capability for long-range dispersion,emphasizing the importance of their eradication to mitigate environmental pollution.While conventional methods for removing chlorinated organic pollutants encompass advanced oxidation,catalytic oxidation,and bioremediation,the utilization of biochar has emerged as a prominent green and efficacious method in recent years.Here we review biochar's role in remediating typical chlorinated organics,including polychlorinated biphenyls(PCBs),triclosan(TCS),trichloroethene(TCE),tetrachloroethylene(PCE),organochlorine pesticides(OCPs),and chlorobenzenes(CBs).We focus on the impact of biochar material properties on the adsorption mechanisms of chlorinated organics.This review highlights the use of biochar as a sustainable and eco-friendly method for removing chlorinated organic pollutants,especially when combined with biological or chemical strategies.Biochar facilitates electron transfer efficiency between microorganisms,promoting the growth of dechlorinating bacteria and mitigating the toxicity of chlorinated organics through adsorption.Furthermore,biochar can activate processes such as advanced oxidation or nano zero-valent iron,generating free radicals to decompose chlorinated organic compounds.We observe a broader application of biochar and bioprocesses for treating chlorinated organic pollutants in soil,reducing environmental impacts.Conversely,for water-based pollutants,integrating biochar with chemical methods proved more effective,leading to superior purification results.This review contributes to the theoretical and practical application of biochar for removing environmental chlorinated organic pollutants.

Residual Levels and New Inputs of Chlorinated POPs in Agricultural Soils from Taihu Lake Region

Selected persistent organochlorine pesticides (OCPs), including 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT) and its principal metabolites 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE) and 1,1-dichloro-2,2-bis(p-chlorophenyl)e- thane (DDD), hexachlorocyclohexane (HCH) and its isomers (α-,β-, γ-, and δ-HCH), hexachlorobenzene (HCB), endo- sulfan, dieldrin, and endrin were quantified to determine current levels of organochlorine pesticides, to assess the eco- toxicological potential, and to distin…

Effective removal of chlorinated organic pollutants by bimetallic iron-nickel sulfide activation of peroxydisulfate

Chlorinated organic pollutants(COPs)have caused serious contaminants in soil and groundwater,hence developing methods to remove these pollutants is necessary and urgent.By a simple hydrothermal method,we synthesized the bimetallic iron-nickel sulfide(FeNiS)particles which exhibited excellent catalytic property of COPs removal.FeNiS was chosen as the peroxydisulfate(PDS)activator to removal COPs including 4-chlorophenol(4-CP),1,4-dichlorophenol(1,4-DCP)and 2,4,6-trichlorophenol(2,4,6-TCP).The results show that FeNiS can efficiently activate PDS to produce sulfate radical(SO4·-)which plays major role in the oxidative dechlorination and degradation due to its strong oxidizing property and the ability of producing hydroxyl radicals(·OH)in the alkaline condition.Meanwhile,the Cl-abscised from COPs during the dechlorination can turn into the chlorine radicals and enhance the degradation and cause further mineralization of intermediate products.This bimetallic FeNiS catalyst is a promising PDS activator for removal of chlorinated organics.

Efficient dechlorination of chlorinated solvent pollutants under UV irradiation by using the synthesized TiO_2 nano-sheets in aqueous phase

Titanium dioxide （TiO2）, which is the widely used photo-catalyst, has been synthesized by simple hydrothermal solution containing tetrabntyl titanate and hydrofluoric acid. The synthesized product has been applied to photo-degradation in aqueous phase of chlorinated solvents, namely tetra- chloroethene （PCE）, tdchloroethene （TCE） and 1,1,l-trichloroethane （TCA）. The photo-degradation results revealed that the degradation of these harmful chemicals was better in UV/synthesized TiO2 system compared to UV/commerciai P25 system and UV only system. The photo-catalytic efficiency of the synthesized TiO2 was 1.4, 1.8 and 3.0 folds higher compared to the commercial P25 for TCA, TCE and PCE degradation, respectively. Moreover, using nitrobenzene （NB） as a probe of hydroxyl radical （.OH）, the degradation rate was better over UV/synthesized TiO2, suggesting the high concentration of .OH generated in UV/synthesized TiO2 system. In addition, .OH concentration was confirmed by the strong peak displayed in EPR analysis over U~/synthesized TiO2 system. The characterization result using XRD and TEM showed that the synthesized TiO2 was in anatase form and consisted of well-defined sheet-shaped structures having a rectangular outline with a thickness of 4 rim, side length of 50 nm and width of 33 nra and a surface 90.3 m^2/g. XPS analysis revealed that ≡Ti-F bond was formed on the surface of the synthesized TiO2. The above results on both photocatalytic activity and the surface analysis demonstrated the good applicability of the synthesized TiO2 nano-sheets for the remediation of chlorinated solvent contaminated groundwater.

Surfactant-assisted removal of 2,4-dichlorophenol from soil by zero-valent Fe/Cu activated persulfate

The organic compounds contaminated soil substantially threatens the growth of plants and food safety.In this study,we synthesis zero-valent bimetallic Fe/Cu catalysts for the degradation of 2,4-dichlorophenol(DCP)in soils with persulfate(PS)in combination of organic surfactants and exploring the main environmental impact factors.The kinetic experiments show that the 5%(mass)dosage of Fe/Cu exhibits a higher degradation efficiency(86%)of DCP in soils,and the degradation efficiency of DCP increases with the increase of the initial PS concentration.Acidic conditions are favorable for the DCP degradation in soils.More importantly,the addition of Tween-80,and Triton-100 can obviously desorb DCP from the soil surface,which enhances the degradation efficiency of DCP in soils by Fe/Cu and PS reaction system.Furthermore,the Quenching experiments demonstrate that SO_(4)^(-1)·and·OH are the predominant radicals for the degradation of DCP during the Fe/Cu and PS reaction system as well as non-radical also exist.The findings of this work provide an effective method for remediating DCP from soils.