Equilibrium,kinetics and thermodynamics of hexavalent chromium biosorption on pristine and zinc chloride activated Senna siamea seed pods

Hexavalent chromium contamination in water is an issue of huge concern due to its use at a high scale, toxicity and non-biodegradability. Biosorption is a cost effective and unconventional strategy for the elimination of Cr(VI). Here, a novel biosorbent Senna siamea seed pod biomass and its chemically activated form have been investigated for the elimination of hexavalent chromium from aqueous solution. The biosorbent was characterized by using BET, FTIR, FESEM-EDX and TGA techniques. Parameters controlling the biosorption process were optimized as pH 2.0, temperature 30°C, initial Cr(VI) concentration 500?mg/L, biosorbent dose 0.5?g/L. Optimized contact time was 210 and 180 min for pristine biomass and activated carbon, respectively. Langmuir isotherm correlated well with experimental data revealing that the biosorption occurred in monolayer pattern. Maximum biosorption capacity calculated by Langmuir biosorption isotherm was 119.18 and 139.86?mg/g for S. siamea pristine biomass and activated carbon, respectively. Pseudo-second order kinetic model correlated well with experimental data. Thermodynamic studies suggested that the biosorption process occurs in a non-spontaneous, stable and endothermic manner. These interesting findings on Cr(VI) biosorption by S. siamea seed pod biomass and S. siamea zinc chloride activated carbon vouches for its potential application as an unconventional biosorbent.     

Circadian consequences of social organization in the ant species<Emphasis Type="Italic"> Camponotus compressus</Emphasis>

The locomotor activity rhythm of different castes of the ant species Camponotus compressus was monitored individually under laboratory light/dark (LD) cycles, and under continuous darkness (DD). The colony of this ant species comprises two sexual castes, the queens and the males, and three worker castes, namely the major, media, and minor workers. The virgin males and virgin queens display rhythmic activity patterns, but the mated queens were arrhythmic while laying eggs, with the rhythmicity resuming soon after egg-laying. Under the LD regime, major workers showed nocturnal patterns, while about 75% of the media workers displayed nocturnal patterns and about 25% showed diurnal patterns. Under the DD regime, most major workers exhibited circadian rhythm of activity with a single steady state, whereas media workers displayed two types of activity patterns, with activity patterns changing after 6–9 days in DD (turn-arounds). The pre-turn-around of the ants that showed nocturnal activity patterns during LD entrainment was <24 h after release into DD, which then became >24 h, after 6–9 days. On the other hand, the pre-turn-around of those ants that exhibited diurnal patterns during LD entrainment was first >24 h after release into DD, and then became <24 h, after 6–9 days. The activity of the minor workers neither entrained to LD cycles nor showed any sign of free-run in DD. It appears that the circadian clocks of the ant species C. compressus are flexible, and may perhaps depend upon the tasks assigned to them in the colony.     

Clocks for sex: loss of circadian rhythms in ants after mating?

This paper describes experiments on the locomotor activity rhythm of queens of the ant species Camponotus compressus, which were performed to investigate the consequences of mating on circadian clocks. Locomotor activity rhythm of virgin and mated queens was monitored individually under constant conditions of the laboratory. The locomotor activity rhythm of virgin queens entrained to a 24 h (12:12 h) laboratory light/dark (LD) cycle and free-ran under constant dim red light (RR) with a free-running period () of approximately 24 h. The locomotor activity of the mated queens on the other hand was arrhythmic during the period when they were laying eggs, and robust rhythmicity appeared soon after the egg-laying phase was over. The of the locomotor activity rhythm of mated queens was significantly greater than that of virgin queens. These results are contrary to the commonly held belief that the role of circadian clocks in ant queens ceases after mating flights, thus suggesting that circadian clocks of ant queens are adaptively plastic and display activity patterns, perhaps depending on their physiological state and tasks in the colony.     

A sustainable system for decontamination of cephalexin antibiotic using electrocoagulation technology and response surface methodology

The emergence of synthetic micropollutants in wastewater due to domestic and industrial use has presented new challenges for treatment processes. Among these pollutants, pharmaceutical and personal care products (PPCPs) are considered emerging contaminants due to their potential to enter drinking water sources. Antibiotics, in particular, are of significant concern due to their high consumption in veterinary and human applications. In this study, the electrocoagulation (EC) process is used as an efficient technique for the removal of cephalexin (CFX) from pharmaceutical wastewater. The study aims to explore the ability of the EC process to remove CFX and optimize its performance using the response surface method based on Central Composite Design (RSM-CCD). The effects of initial CFX concentration, electrolysis time, initial pH, and electrode type (non-insulated and insulated) were considered in the optimization process. This research is distinct as it examines the influence of key factors on the elimination of CFX. The results showed that electrolysis time had the most significant effect on CFX removal using the EC process. The analysis of variance (ANOVA) test was used to evaluate the importance of independent variables and their interaction. The optimal operating conditions for maximum removal efficiency (86.53%) were an initial CFX concentration, reaction time, and initial pH of 34 mg/L, 34.35 min, and 6.5, respectively, using an insulated electrode. Under these optimal conditions, predicted CFX removal was 93.54%. These findings demonstrate that RSM-CCD is a useful tool for optimizing electrochemical removal processes for micropollutants such as CFX from wastewater streams. The study highlights the importance of considering electrode type in optimizing EC processes for micropollutant removal from wastewater.