Thermo-chemical behaviour of Dunaliella salina biomass and valorising their biochar for naphthalene removal from aqueous rural environment.

Thermo-chemical behavior of a microalgal biomass; Dunaliella salina was investigated through thermo-gravimetric analyses. Fully-grown D. salina biomass were subjected for biochar conversion using pyrolytic treatment at three distinct heating rates such as 2.5, 5, and 15 °C min-1. The kinetic appraisals were explained by using model-free kinetics viz., Kissinger-Akahira-Sanose, Flynn-Waal-Ozawa and Starink iso-conversional correlations with concomitant evaluation of activation energies (Ea). The Ea value is 194.2 kJ mol-1 at 90% conversion in FWO model, which is higher as compared to other two models. Moisture, volatile substances, and other biochemical components of the biomass were volatilized between 400 and 1000 K in two separate thermo-chemical breakdown regimes. Microscopic and surface characterization analyses were carried out to elucidate the elemental and morphological characteristics of the biomass and biochar. Further, the proficiency of the prepared biochar was tested for removing naphthalene from the watery media. The novelty of the present study lies in extending the applicability of biochar prepared from D. salina for the removal of a model polyaromatic hydrocarbon, naphthalene.

Synthesis and characterization of rhamnolipid based chitosan magnetic nanosorbents for the removal of acetaminophen from aqueous solution.

Biocatalytically synthesized mono-rhamnolipids are eco-friendly surfactants that exhibit strong industrial applications owing to their low toxicity and biodegradability as well as their efficient antimicrobial and surface tension reduction potential. In this present study, novel adsorbent chitosan encapsulated magnetic nanoparticles coated with rhamnolipids (Rh-cMNP) were prepared and used for the adsorption of the micropollutant acetaminophen. The SEM, FTIR, and VSM results showed that Rh-cMNP had abundant functional groups with a mesoporous feature and easy separation of the magnetic nanosorbent from the reaction mixture. The obtained nanosorbent was effectively used to remove acetaminophen, one of the most common persistent pharmaceutical pollutants in the environment. Optimization studies revealed the maximum removal of 96.7% acetaminophen with the ability of adsorption to be 96.3 mg/g at 60 min of contact time and process parameters of pH 5.0 and 303 K temperature. Langmuir isotherm was most favourable for the optimized data; kinetic studies obeyed pseudo-second-order whose feasibility and thermodynamic studies obtained spontaneity. Regeneration of used Rh-cMNP is performed with 0.1 N HCl/NaOH and observed to be consistent for eight adsorption-desorption cycles.

Kinetics, equilibrium and thermodynamic investigations of methylene blue dye removal using Casuarina equisetifolia pines.

Casuarina equisetifolia pines are degradable biopolymeric substance with dye-sequestering property was utilized as biosorbent to expel a cationic dye; methylene blue dye from simulated wastewater. The prepared adsorbent material was characterized for their structural, morphological and elemental features to understand their suitability in augmenting in dye-wastewater remediation. The results infer that 0.5 g/L biosorbent was proficient in removing 100 mg/L methylene blue (pH 7.0 ± 0.2) when agitated at 150 rpm for 120 min. Isothermal behavior were evaluated using non-linear isotherm models like Temkin, Langmuir and Freundlich models while the rate-limiting steps were found using kinetic models. Temkin isotherm and pseudo-first order model explained the removal mechanism among the models evaluated, which infers that the biosorption followed physisorption with the maximum adsorption capacity of 41.35 mg/g. Thermodynamic behavior of methylene blue removal by C. equisetifolia pines powder described the feasibility of biosorption as well as the type of heat involved. Equilibrium sorption capacities, rate constants and correlation coefficients explains that MB dye removal by C. equisetifolia pines is presumably physisorption, spontaneous and endothermic in nature.