Adsorption of Pb2+ from aqueous solution by modified melon (Citrullus lanatus) seed husk.

The application of Modified Melon Seed Husk (MMH) an agricultural waste in the remediation of water contaminated with lead ions was investigated in the present study. Modification was done by soaking the melon seed husk in 0.5M NaOH solution. Batch kinetic and isotherm studies was performed to understand the ability of the adsorbents. Effect of some process variables were assessed viz: pH, initial metal ion concentration and sorbent dosage on the sorption process. The equilibrium sorption isotherm was studied using the Freundlich and Langmuir isotherm models. The results obtained showed that the process of the sorption fitted better with the Freundlich isotherm, implying that the sorption occurred on a heterogeneous surface of the MMH. The monolayer adsorptioncapacity determined from the Langmuir adsorption equation was found to be 52.08 mg/g which competes favourable with some other biosorbents. Data obtained from the kinetics of the sorption process via initial metal ion concentration were analyzed using pseudo second order, the pseudo first order model and intraparticle diffusion model. The sorption process obeyed the pseudo second order kinetic model better than the pseudo first order kinetic model, thus suggesting the role of chemisorption in the mechanisms of the sorption. The intraparticle diffusion model showed that intraparticle diffusion is not the singular rate limiting step in the sorption process. The kinetic parameters suggest that adsorption of lead ions by MMH was favourable. Overall, the present findings suggest that MMH, an environmentally friendly, efficient and low-cost biosorbent is useful for the removal of Pb2+ from aqueous media. Key words: Adsorption, Isotherm, Kinetics, Lead, Melon seed Husk, Wastewate

Adsorptive Removal of Cd2+ and Zn2 From Aqueous System by BSG

The potential utilization of Brewer’s Spent Grain (BSG) was investigated in the removal of Cadmium and Zinc from aqueous system. Batch sorption process assessment of the effects of process variables showed that pH, initial metal ion concentration and dosage amount affect the sorption and uptake of Cd and Zn ions by BSG. Analysis of the sorption process using different kinetic models showed that the pseudo first order kinetic models gave poor descriptions of the process for Zn  was r2 = 0.5268 but a good one for Cd at r2 = 0.9618 while the pseudo second order kinetic model gave a good description of the process for both metal ions  (r2>0.98). The Pseudo second order rate constant obtained for Zn (1.0812mgg-1min-1) is than that for Cd (0.17mgg-1min-1).Equilibrium isotherm analysis of the sorption process data showed that the Langmuir isotherm gave a better description of the process than the Freundlich for Cd while both Freundlich and Langmuir fitted very well for Zn sorption by BSG. The results of the studies indicate that the metal ions were favourably adsorbed onto the adsorbent with a removal efficiency of 94.46% for Zn and 77.81% for Cd. Keywords: Brewer’s Spent Grain, cadmium, zinc, sorption, Isotherm, Kinetics

Optimizing the searches for interstellar heterocycles

It is a fact that interstellar formation processes are thermodynamically affected. Based on this, the seven heterocycles; imidazole, pyridine, pyrimidine, pyrrole, quinoline, isoquinoline and furan that have been searched for from different astronomical sources with only upper limits of their column density determined without any successful detection remain the best candidates for astronomical observation with respect to their isomers. These molecules are believed to be formed on the surface of the interstellar dust grains and as such, they are susceptible to interstellar hydrogen bonding. In this study, a two way approach using ab initio quantum chemical simulations is considered in optimizing the searches for these molecules in interstellar medium. Firstly, these molecules and their isomers are subjected to the effect of interstellar hydrogen bonding. Secondly, the deuterated analogues of these heterocycles are examined for their possible detectability. From the results, all the heterocycles except furan are found to be strongly bonded to the surfaces of the interstellar dust grains thereby reducing their abundances, thus contributing to their unsuccessful detection. Successful detection of furan remains highly feasible. With respect to their D-analogues, the computed Boltzmann factor indicates that they are formed under the dense molecular cloud conditions where major deuterium fractionation dominates implying very high D/H ratio above the cosmic D/H ratio which suggests the detectability of these deuterated species. © 2021 COSPA