Experimental study on removal of chromium using nano-silica coated pyrolysed biochar in batch, fixed bed and fluidized bed reactor: Synthesis, characterization, experimentation and mechanism

Nowadays Nano technology is used as one of the alternative for removal of pollutants. In this study, raw sawdust was used as biomass and was pyrolyzed at high temperature in an inert environment. The synthesized char was finally coated with nano-silica in a Teflon coated hydrothermal reactor. The characterization of the synthesized composite was performed. Nano silica coated (AcSi) activated carbon was further used to reduce Cr+6 in three type of reactors (batch, fixed bed and fluidized bed reactor). With increased in concentration of Cr+6, the fluidization behaviour in case of Fluidized reactor and the breakthrough time in case of fixed bed reactor was decreasing. Reaction time and availability of the active surface group played an important role in both fixed and fluidised bed reactor and observed that biochar coated with nano-silica was capable to remove pollutants efficiently using all the reactor. The batch study suggested monolayer adsorption and exothermic reaction and maximum adsorption capacity was observed as 88.2 mg/g and removal was 99.8% after 120 min. Regeneration study suggested that the composite can be regenerated with alkali solution and upto 5 cycles this composite can be used

Treatment of Wastewater from a Dairy Industry Using Rice Husk as Adsorbent: Treatment Efficiency, Isotherm, Thermodynamics, and Kinetics Modelling

Effluent from milk processing unit contains soluble organics, suspended solids, and trace organics releasing gases, causing taste and odor, and imparting colour and turbidity produced as a result of high consumption of water from the manufacturing process, utilities and service section, chemicals, and residues of technological additives used in individual operations which makes it crucial matter to be treated for preserving the aesthetics of the environment. In this experimental study after determination of the initial parameters of the raw wastewater it was subjected to batch adsorption study using rice husk. The effects of contact time, initial wastewater concentration, pH, adsorbent dosage, solution temperature and the adsorption kinetics, isotherm, and thermodynamic parameters were investigated. The phenomenon of adsorption was favoured at a lower temperature and lower pH in this case. Maximum removal as high as 92.5% could be achieved using an adsorbent dosage of 5 g/L, pH of 2, and temperature of 30°C. The adsorption kinetics and the isotherm studies showed that the pseudo-second-order model and the Langmuir isotherm were the best choices to describe the adsorption behavior. The thermodynamic parameters suggested that not only was the adsorption by rice husk spontaneous and exothermic in nature but also the negative entropy change indicated enthalpy driven process

Microbial biofilter for toluene removal: Performance evaluation, transient operation and theoretical prediction of elimination capacity

Toluene contributes a major part amongst the hazardous volatile organic compounds (VOCs). In this present work, toluene removal in a novel lab scale biofilter packed with ceramic beads and compost has been studied after 20 d of acclimatization. For different initial toluene concentrations (0.2–3.7 g m−3), the elimination capacity (EC) and removal efficiency (RE) are studied. A maximum EC of 96 g m−3 h−1 was found at the toluene inlet loading rate of 98.8 g m−3 h−1 with high RE of 97% during its 22 d continuous operation. The removal of toluene biofilter was better at the entry section of the contaminated air. The study also showed stability of biofilter during transient operation in treating toluene. The experimental EC values are compared with theoretical EC values from mathematical model. The theoretical average biofilm thickness was found to be 0.47 mm. The Ottengraf mathematical model was able to predict the theoretical EC at different regime of biofilter operations. Keywords: Biofilter, Performance, Transient condition, Ottengraf model, Biofilm thicknes