Adsorption of 2-mercaptobenzothiazole from aqueous solution by organo-bentonite

The adsorption behavior of 2-mercaptobenzothiazole onto organo-bentonite was investigated. Natural bentonite from Gaozhou in Guangdong Province, China was collected. Organo-bentonite was prepared by intercalation of cetyltrimethyl ammonium bromide into the natural bentonite. The physicochemical properties of the prepared organo-bentonite were characterized by X-ray diffraction, N2 adsorption-desorption isotherm and Fourier transform infrared spectroscopy. The results showed that montmorillonite is the main component of the natural bentonite. The basal spacing of the natural bentonite is 1.47 nm, which increased to 1.98 nm on intercalation with cetyltrimethyl ammonium bromide. Moreover, both the surface area and pore volume increased with intercalation. Clear CH2 stretching （3000-2800 cm-1） and scissoring （1480-1450 cm-1） modes of the intercalated surfactants were observed for organo- bentonite. Compared with the pseudo first-order kinetic model, the pseudo second-order kinetic model is more suitable to describe the adsorption kinetics of 2-mercaptobenzothiazole onto organo-bentonite. The adsorption capacity of 2-mercaptobenzothiazole onto organo-bentonite increased with increasing initial concentration of 2-mercaptobenzothiazole, but decreased with increasing adsorbent dosage. The adsorption isotherm of 2-mercaptobenzothiazole onto organo-bentonite fits well with the Langmuir model. The maximum adsorption capacity of organo-bentonite for 2-mercaptobenzothiazole was 33.61 mg/g, indicating that organo-bentonite is a promising adsorbent for 2-mercaptobenzothiazole.

Effect of environmental C/N ratio on activities of lignin-degrading enzymes produced by Phanerochaete chrysosporium

Lignin-degrading enzymes secreted by white rot fungi play an important role in the degradation of lignin and persistent organic pollutants(POPs).In this study,effect of environmental C/N ratio on the activities of lignin-degrading enzymes,lignin peroxide(Li P)and manganese peroxidase(Mn P),produced by Phanerochaete chrysosporium,a white rot fungus,was investigated.Glucose was used as C source,and ammonium tartrate of different concentrations was used as N source to provide different C/N ratios.Relationships between Li P and Mn P activities and environmental C/N ratio were explored.The results showed that the higher the N source concentration,the faster the mycelium pellets aged.The faster the mycelium dry weight increased,the higher the Li P and Mn P activities.A high C/N ratio was a necessary condition for the secretion of Li P or Mn P.In addition,mycelium dry weight essentially affected enzyme activities.In the 122 C/N ratio and 50 C/N ratio treatments,mycelium dry weight essentially affected Mn P activity and both Li P and Mn P activities,respectively.

Toxicity effects of disinfection byproduct chloroacetic acid to Microcystis aeruginosa: Cytotoxicity and mechanisms

Chlorine-based disinfectants are widely used for disinfection in wastewater treatment.The mechanism of the effects of chlorinated disinfection by-products on cyanobacteria was unclear.Herein,the physiological effects of chloroacetic acid(CAA)on Microcystis aeruginosa(M.aeruginosa),including acute toxicity,oxidative stress,apoptosis,production of microcystin-LR(MC-LR),and the microcystin transportation-related gene mcyH transcript abundance have been investigated.CAA exposure resulted in a significant change in the cell ultrastructure,including thylakoid damage,disappearance of nucleoid,production of gas vacuoles,increase in starch granule,accumulation of lipid droplets,and disruption of cytoplasm membranes.Meanwhile,the apoptosis rate of M.aeruginosa increased with CAA concentration.The production of MC-LR was affected by CAA,and the transcript abundance of mcyH decreased.Our results suggested that CAA poses acute toxicity to M.aeruginosa,and it could cause oxidative damage,stimulate MC-LR production,and damage cell ultrastructure.This study may provide information about the minimum concentration of CAA in the water environment,which is safe for aquatic organisms,especially during the global coronavirus disease 2019 pandemic period.

Reply to comments on “Adsorption of 2-mercaptobenzothiazole from aqueous solution by organo-bentonite” by Yuhshan Ho

There were several first-order kinetic equations used and cited by previous publications （Do,an et al., 2007; Eftekhari et al., 2010; Lagergren, 1898; Kannan and Sundaram, 2001;Ozcan et al., 2006）：