Biogenic Synthesis, Characterization, and Photocatalytic Evaluation of Pristine and Graphene-Loaded Zn50Mg50O Nanocomposites for Organic Dyes Removal.

Algal biomass synthesised nanocomposites have a higher surface area and reusability advantages. This study aimed to synthesise and characterise ZnMgO and silica-supported graphene with ZnMgO (G-ZnMgO) nanocomposites from Kappaphycusalvarezii and evaluate their potential in the application of photocatalysis to remove Rhodamine-B (RhB) and methylene blue (MB) dyes from their aqueous medium by maximising the percentage removal using response surface methodology (RSM) modelling. Nanocomposites were synthesised and characterised by biogenic and instrumental (Powder X-ray diffraction (P-XRD), electron microscopic analysis (SEM and TEM), Fourier transform infrared spectroscopy (FTIR), Energy dispersive analysis of X-rays (EDAX). and UV-visible diffuse reflectance spectroscopy (UV-DRS)) methods, respectively; modelling predicted the optimal conditions to be photocatalyst dosage and contact time of 1 g/L and 90 min, respectively, to obtain maximum MB dye removal of 80% using G-ZnMgO. The results showed the best fit between experimental and RSM predicted values. Thus, the obtained results conclude that the algal biomass synthesised nanocomposites were found to be one of the potential photocatalysts for the removal of RhB and MB dyes from their aqueous solution.

Ecofriendly biopolymers and composites: Preparation and their applications in water-treatment.

Over the past few decades, the term polymer has been repeatedly used in several industries for their immense characteristics in different applications. Polymers and their composites which were prepared from chemical monomer sources turned out to be potentially harmful to the environment due to their tedious degradation process. Biopolymers are natural substitutes for synthetic polymers which can be efficiently extricated from natural sources. They are predominantly available as polymeric units as well as monomeric units that are linked covalently. These environment-friendly biopolymers and their composites can be categorized based on their numerous sources, different methods of preparation and their potential form of usage. They were found to be biocompatible and biodegradable which make them exceptionally useful in environment based applications, mainly in the process of water treatment, both potable and wastewater. Further, the biopolymer and biopolymer composites easily fit into different parts of the treatment process by acting as filtration media, adsorbents, coagulants and as flocculants. The primary focus of this review is to provide a comprehensive information of biopolymers and biopolymer composites from synthesis to their usefulness for their productive application in water treatment processes. On the whole, it can be substantiated that the biopolymers were identified to play a notable adversary to the synthetic polymers in treating waters with an indispensable need for an elaborative study in the production of the biopolymers.

Use of chicken feather and eggshell to synthesize a novel magnetized activated carbon for sorption of heavy metal ions.

Keeping environment and sustainability concept in view with preparation of new sorbents, two waste by-products from the poultry industry, i.e. feather and eggshell, were used for synthesis of a new magnetic activated carbon for sorption of heavy metal ions. Using response surface methodology based central composite design (RSM-CCD) technique, chicken feather and acid-digested eggshell were used as precursor and activation material, respectively, for the synthesis of the herein studied activated carbon (eggshell activated chicken feather carbon; ESCFC). The prepared activated carbon was magnetized for easy separation from water media, and iron oxide magnetized ESCFC (IOM-ESCFC) was comprehensively examined for removing some heavy metallic ions (Pb2+, Cd2+, Cu2+, Zn2+, and Ni2+) from water. The maximum mono-layer sorption capacities and the highness of sorption speed, along with thermodynamic studies, demonstrated that IOM-ESCFC can be regarded as a potential adsorbent against heavy metal ions from waters and wastewaters.

Process design and optimization of bioethanol production from cassava bagasse using statistical design and genetic algorithm.

Bioethanol production from agro-industrial residues is gaining attention because of the limited production of starch grains and sugarcane, and food-fuel conflict. The aim of the present study is to maximize the bioethanol production using cassava bagasse as a feedstock. Enzymatic liquefaction, by α-amylase, followed by simultaneous saccharification and fermentation (SSF), using glucoamylase and Zymomonas mobilis MTCC 2427, was investigated for bioethanol production from cassava bagasse. The factors influencing ethanol production process were identified and screened for significant factors using Plackett-Burman design. The significant factors (cassava bagasse concentration (10-50 g/L), concentration of α-amylase (5-25% (v/v), and temperature of fermentation (27-37 °C)) were optimized by employing Box-Behnken design and genetic algorithm. The maximum ethanol concentrations of 25.594 g/L and 25.910 g/L were obtained from Box-Behnken design and genetic algorithm, respectively, under optimum conditions. Thus, the study provides valuable insights in utilizing the cost-effective industrial residue, cassava bagasse, for the bioethanol production.

Efficient mercury removal from wastewater by pistachio wood wastes-derived activated carbon prepared by chemical activation using a novel activating agent.

Ammonium nitrate (NH4NO3) with explosive characteristics at high temperatures was used as a novel activating reagent to prepare a surface-engineered activated carbon derived from pistachio wood wastes (PWAC). PWAC was characterized and compared with commercial activated carbon (CAC) by textural and morphological properties, surface chemistry, crystal structure, and surface elemental composition. The results indicated that the optimal conditions of PWAC preparation to obtain the highest mercury adsorption capacity were pyrolysis temperature (800 °C), pyrolysis time (2 h), and impregnation ratio (5%). PWAC was of highly regular-shaped and well-developed pores and possessed a large surface area (1448 m2/g) and high total pore volume (0.901 cm3/g). The batch experiments indicated that the adsorption process of Hg(II) was strongly dependent on the solution pH and reached fast equilibrium at approximately 30 min. PWAC (202 mg/g) exhibited a significantly higher maximum adsorption capacity than commercial activated carbon (66.5 mg/g). Adsorbent-adsorbate dispersion interaction plays a major role in the adsorption mechanism, compared to the minor role played by pore filling and reduction mechanism. Overall, ammonium nitrate can be considered a newer activating reagent to prepare promising and low-cost PWAC for effectively Hg(II) removal from water media.

Adsorption property of Br-PADAP-impregnated multiwall carbon nanotubes towards uranium and its performance in the selective separation and determination of uranium in different environmental samples.

A newer efficient U(VI) ion adsorbent was synthesized by impregnating Br-PADAP [2-(5-Bromo-2-pyridylazo)-5-(diethylamino)phenol] onto multiwall carbon nanotubes (MWCNTs). The effects of various operation conditions on uranium adsorption (i.e., pH contact time, temperature, and initial uranium concentration) were systematically evaluated using batch experiments. The results indicated that the uranium adsorption on modified MWNCTs (5.571 × 10-3g/mg × min) reached faster equilibrium than that on pristine MWNCTs (4.832 × 10-3g/mg × min), reflecting the involvement of appropriate functional groups of Br-PADAP on the chelating ion-exchange mechanism of U(VI) adsorption. Modified MWNCTs (83.4mg/g) exhibited significantly higher maximum Langmuir adsorption capacity than pristine MWNCTs (15.1mg/g). Approximately 99% of uranium adsorbed onto modified MWNCTs can be desorbed by 2.5mL of 1M HNO3 solution. Therefore, Br-PADAP-modified MWNCTs can server as a promising adsorbent for efficient uranium adsorption applications in water treatment. Subsequently, the proposed solid-phase extraction (using a mini-column packed with Br-PADAP/MWCNT) was successfully utilized for analysing trace uranium levels by the ICP-AES method in different environmental samples with a pre-concentration factor of 300-fold. The coexistence of other ions demonstrated an insignificant interference on the separative pre-concentration of uranium. the detection limit was recognized as 0.14µg/L, and the relative standard deviation was approximately 3.3% (n = 7).