Total Phosphorus and Reactive Phosphate Removal from Aquaculture Wastewater using Calcined Eggshell

Phosphorus is the key nutrient in fish feed, and it has been one of the major soluble nutrients found in aquaculture wastewater (AW). This work aims to evaluate the removal of Total Phosphorus (TP) and Reactive Phosphate (PO4 3-) via adsorption in batch studies using thermally calcined eggshell as adsorbent. The effect of calcination temperature (700 – 1000°C), particle size and holding time were investigated. The screening phase showed that calcined eggshell at 800 °C for 30 minutes was the most suitable condition. Characterization of adsorbents revealed that crystalline structure and functional groups were responsible for the TP and PO4 3- removal using calcined eggshell from AW. Adsorption equilibrium was attained after 15 min with the dosage of 0.2 g of the optimized adsorbent, capable of removing more than 97 % of TP and PO4 3- from AW. This finding has proven the ability of calcined eggshell waste as a potential phosphorus adsorbent from liquid effluents.

Co-Production of Isoprene and Lactate by Engineered Escherichia coli in Microaerobic Conditions

Lactate and isoprene are two common monomers for the industrial production of polyesters and synthetic rubbers. The present study tested the co-production of D-lactate and isoprene by engineered Escherichia coli in microaerobic conditions. The deletion of alcohol dehydrogenase (adhE) and acetate kinase (ackA) genes, along with the supplementation with betaine, improved the co-production of lactate and isoprene from the substrates of glucose and mevalonate. In fed-batch studies, microaerobic fermentation significantly improved the isoprene concentration in fermentation outlet gas (average 0.021 g/L), compared with fermentation under aerobic conditions (average 0.0009 g/L). The final production of D-lactate and isoprene can reach 44.0 g/L and 3.2 g/L, respectively, through fed-batch microaerobic fermentation. Our study demonstrated a dual-phase production strategy in the co-production of isoprene (gas phase) and lactate (liquid phase). The increased concentration of gas-phase isoprene could benefit the downstream process and decrease the production cost to collect and purify the bio-isoprene from the fermentation outlet gas. The proposed microaerobic process can potentially be applied in the production of other volatile bioproducts to benefit the downstream purification process.

Designing of Fabric Reinforced Polymer in the Assessment of Sorption Capacity of Mussel Shell Powder for Divalent Ion: GIS Mapping and Statistical Studies

This paper discusses the efficiency of acid modified mollusc shell powder in adsorbing Zn(II) ions from synthetic wastewater and actual wastewater samples discharged from electroplating industries. The chemically treated adsorbent was characterized in terms of structure and surface properties. The parameters such as, size of the sorbent particles, dosage, initial Zn(II) concentration, temperature, contact time pH and temperature were varied for optimization using batch studies. The adsorbate-adsorbent system was studied by Langmuir, Freundlich, Tempkin and DKR isotherms. The adsorption experiments were conducted in a column packed with the acid modified mollusc shell powder. Further, real wastewater samples having Zn(II) concentration higher than the permissible levels were collected from the industrial belt in Coimbatore, to assess the potential of the bio adsorbent. A fiber reinforced polymer fabricated with the adsorbent material installed at the effluent discharge plants achieved 100% Zn(II) removal from electroplating wastewaters. Statistical analysis performed using SPSS software showed significant correlation among the input parameters and the analytical results post-adsorption.

Batch Adsorption Assessment of Neem Nut Carbon for Abating Chromium(VI) in Wastewater

Discharge of Cr(VI) laden effluents is highly toxic and decontaminating the wastewater from Cr(VI) is necessary for Environmental Protection. An investigation on the adsorption characteristics of activated carbon prepared from neem nut (NNC) for the removal of Cr(VI) from wastewater by varying the parameters such as carbon dose, pH, equilibration time by batch studies was found to be effective for the removal of Cr(VI) from wastewater. Carbon characteristics of activated neem nut carbon were ascertained. Evaluation were done by varying the pH from 1 to 6, carbon dose from 0.1 g to 0.5 g and equilibration time from 1 to 6 hours. Maximum Cr(VI) removal of 95% took place when batch studies were done at an optimal pH of 2, carbon dose of 0.2 g//100mL, and equilibration time of 4 hours. Freundlich and Langmuir adsorption isotherm models were considered for analysis.

The key role of contact time in elucidating the mechanisms of enhanced decontamination by Fe0/MnO2/sand systems

Metallic iron (Fe0) has shown outstanding performances for water decontamination and its efficiency has been improved by the presence of sand (Fe0/sand) and manganese oxide (Fe0/MnOx). In this study, a ternary Fe0/MnOx/sand system is characterized for its discoloration efficiency of methylene blue (MB) in quiescent batch studies for 7, 18, 25 and 47 days. The objective was to understand the fundamental mechanisms of water treatment in Fe0/H2O systems using MB as an operational tracer of reactivity. The premise was that, in the short term, both MnO2 and sand delay MB discoloration by avoiding the availability of free iron corrosion products (FeCPs). Results clearly demonstrate no monotonous increase in MB discoloration with increasing contact time. As a rule, the extent of MB discoloration is influenced by the diffusive transport of MB from the solution to the aggregates at the bottom of the vessels (test-tubes). The presence of MnOx and sand enabled the long-term generation of iron hydroxides for MB discoloration by adsorption and co-precipitation. Results clearly reveal the complexity of the Fe0/MnOx/sand system, while establishing that both MnOx and sand improve the efficiency of Fe0/H2O systems in the long-term. This study establishes the mechanisms of the promotion of water decontamination by amending Fe0-based systems with reactive MnOx.

PHYTOPRODUCTION OF IRON NANOPARTICLES FOR METHYL ORANGE REMOVAL AND ITS OPTIMIZATION STUDIES

In the present study, iron nanoparticles have been synthesized using the leaf extract of potential weed Datura inoxia to evaluate their feasibility for methyl orange removal. This method approves that the green synthesis method must be adopted for the more efficient and rapid synthesis of metal nanoparticles. A simple process of bio reduction has been involved, the leaf extract of Datura inoxia used as a precursor for reducing metal iron. The UV- visible spectral analyses for iron nanoparticles have shown a peak at 240 nm wavelength. Spherical shaped iron nanoparticles are formed as shown by transmission electron microscopy. Batch studies were investigated for optimization study of methyl orange removal on selected parameters i.e., pH (1-10), adsorbent dose (0.02-0.14g), initial dye concentration (5-100pm), contact time (15-120 minutes) and temperature (20- 50o C). The result from the present study approves easy and fast dye removal of 98 % with kinetic data following a second order removal rate. The thermodynamics parameters supported the spontaneity with a negative value of ?G i.e., -14.87 kJ mol-1 and exothermic (?H -7.094 kJ mol-1) nature of the reaction. Thus, it can be concluded that the use of Datura inoxia for the phyto production of iron nanoparticles is efficient for various commercial applications in environment sector

Biochar from Pine Wood, Rice Husks and Iron-Eupatorium Shrubs for Remediation Applications: Surface Characterization and Experimental Tests for Trichloroethylene Removal

Nowadays porous materials from organic waste, i.e., Biochar (BC), are receiving increased attention for environmental applications. This study adds information on three BCs that have undergone a number of studies in recent years. A Biochar from pine wood, one from rice husk and one from Eupatorium shrubs enriched with Iron, labelled as PWBC, RHBC and EuFeBC respectively, are evaluated for Trichloroethylene (TCE) removal from aqueous solution. Physical-chemical description is performed by SEM-EDS and BET analysis. The decrease of TCE over time follows a pseudo-second order kinetics with increased removal by the PWBC. Freundlich and Langmuir models well fit equilibrium test data. The optimized values of the maximum adsorbed amount, qmax (mg g−1), follows this order 109.41 PWBC > 30.35 EuFeBC > 21.00 RHBC. Fixed-bed columns are also carried out. Best performance is again achieved by PWBC, which operates for a higher number of pore volume, followed by EuFeBC and RHBC. Continuous testing confirms batch studies and makes it possible to evaluate the workability of materials in configurations closer to reality. Results are promising for potential environmental application. In particular, the characterization of several classes of contaminants opens the doors to possible uses in mixed contamination cases.