Efficient removal of cationic dyes using lemon peel-chitosan hydrogel composite: RSM-CCD optimization and adsorption studies.

The most prominent and easily identifiable factor of water purity is its colour, which may be both physically undesirable, and act as an alert towards potential environmental contamination. The current study describes the optimum synthesis technique for Lemon Peel-Chitosan hydrogel using the Response Surface Methodology integrated Central composite Design (RSM-CCD). This adsorbent is both environmentally friendly and cost-effective. The hydrogel exhibited a maximal dye removal capacity of 24.984, 24.788, 24.862, 23.483, 24.409, and 24.726 mg g-1, for 10 mg L-1 aqueous medium of Safranin O, Methylene blue, Basic fuchsin, Toluidine blue, Brilliant green and Crystal violet, respectively. The adsorption kinetics and isotherm data suggest that the Pseudo second-order kinetic and Freundlich adsorption isotherm models precisely represent the respective behaviour of all the dyes. The thermodynamic viability of the process is determined by the values of ΔG, ΔH, and ΔS. The probable mechanism of adsorption was the electrostatic interaction between the dye molecules and the hydrogel. The regenerated hydrogel had removal efficiencies of over 80 % even after enduring six cycles. Hence, the exceptional recyclability and utility of the adsorbent show their sustainability for wastewater treatment in textile factories.

Evaluation of heavy metal contaminants in prepared noodles: source allocation and health risk assessment.

In recent years, special attention has been given to emission research that led to the deposition of toxicants from road traffic. Thus, it is imperative to focus on heavy metal (HM) stressors in food items, their source contribution, and health risk assessment providing insight into their spatial role at the population level. In this study, heavy metal in the street vended noodles was studied while correlating the quality of noodle with different environmental origins. The samples were prepared using acid digestion and analysed by flame atomic absorption spectrophotometer, except Hg which was analysed by direct mercury analyser. The results showed that some heavy metals like Cr, Pb, Mn, Cd, and Hg exceed their permissible limits established by the international legislation for food products. In the noodle samples, the concentration of heavy metal ranged from < 0.1 to 0.904 mg/kg for Pb, < 0.09 to 0.843 mg/kg for Ni, < 0.004 to 0.201 mg/kg for Cd, < 0.0001 to 0.004 mg/kg for Hg, < 0.01 to 1.388 mg/kg for Cu, < 0.015 to 8.049 mg/kg for Mn, and < 0.02 to 16.514 mg/kg for Cr. Noodle samples vended on high traffic density streets are directly associated with increased HM content due to atmospheric deposition from the surrounding. Source apportionment study determines that HM contamination belongs to the same source of origin, except Cr. Based on the cluster analysis, these samples fall into three major groups that were further validated by the canonical discriminant function. Health risk prediction by Monte Carlo simulation revealed an elevated non-carcinogenic health hazard risk to consumers with a hazard index (HI) shift from 71 to 75%. Health hazard analysis showed that consumers of high traffic density street vended food are at higher risk of developing health-related issues. This study is important to evaluate the health risk of the population exposed to heavy metals due to ingestion of street vended food.

Synthesis of Biomass-Derived Activated Carbons and Their Immobilization on Alginate Gels for the Simultaneous Removal of Cr(VI), Cd(II), Pb(II), As(III), and Hg(II) from Water.

Low-cost alginate gels of activated carbons were prepared, which were derived from the peels of banana and sweet lime. The synthesized carbon was activated and immobilized on alginate, producing its gel. These gels were categorized according to their methods of drying, in which air drying, freeze drying, and supercritical drying led to the formation of xerogels, cryogels, and aerogels, respectively. The gels were used for adsorption of heavy metals from their aqueous solution. The heavy metals that were targeted for removal were Pb(II), Cd(II), Cr(VI), As(III), and Hg(II). Among all the adsorbents, the alginate cryogel of sweet lime-derived activated carbon (SLACC) showed the highest removal percentage of heavy metals, and thus, it was used for batch study. The adsorption of heavy metals by SLACC was checked at different times, pH values, adsorbent doses, temperatures, and adsorbate concentrations. The study revealed that the pseudo-second-order model best described the kinetic study, while the adsorption followed the Freundlich isotherm. SLACC showed maximum adsorption capacities (q cal) of 3.71, 4.22, 20.04, 7.31, and 4.37 mg/g for Cr, Cd, Pb, As, and Hg, respectively, when 20 mg of SLACC was used for the removal of 4 ppm concentration of the targeted heavy metals from their 20 mL solution. Based on the thermodynamic study, it was found that the adsorption was spontaneous and exothermic. Furthermore, the adsorbent was also used on real water samples and showed up to 90% removal efficiency for these targeted heavy metals. SLACC was regenerated with 0.1 M ethylenediaminetetraacetic acid (EDTA) solution and reused for five cycles, in which the percentage removal of heavy metals was more than 50% till the fourth cycle. Furthermore, the leaching study showed that no toxic elements had leached from SLACC into water, making it a safe adsorbent.