Sustainable polyurethane for the remediation of oil spills: a review.

Catastrophic oil spill is one of the major issues to the environment. Various methods have been used to treat oil spillage including in situ burning, the use of skimmers, dispersants, bioremediation, dispersing agents, oil sorbents, and biological agents. Application of oil sorbent is one of the effective solutions in oil spill clean-up. Polymers are sustainable extraordinary materials for the treatment of oil spillage due to their special physicochemical characteristics such as high porosity, good hydrophobicity, and reusability. Polymers are modified using suitable chemical reagents and their hydrophobicity is enhanced, making them suitable for oil spill clean-up. The present manuscript is an attempt to summarize the study of chemical modifications done on a polymer polyurethane (PU) for achieving the desirable properties, for efficient oil spill clean-up. A patent analysis has been carried out for the leading countries, top inventors, leading assignees, trends of patent publications, citation analysis, and summary of granted patents in the area of the use of a polymer Polyurethane (PU) for oil spill clean-up.

Emerging advances of composite membranes for seawater pre-treatment: a review.

As the population continues to grow, the preservation of the world's water resources is becoming a serious challenge. The seawater desalination process is considered a sustainable option for the future. The two most common technologies used in desalination are reverse osmosis (RO) and membrane distillation (MD). However, membrane fouling caused by the accumulation of contaminants on the membrane surface is an emerging and growing problem. A pre-treatment stage is required to reach optimal efficiency during the desalination process since this stage is crucial for a successful desalination process. In this regard, the development of new material-based composite membranes has the potential to upgrade the anti-fouling features of RO membranes thereby enhancing desalination efficiency due to their high permeability, hydrophilicity, selectivity mechanical strength, thermal stability, and anti-bacterial properties. The objective of this review is to present various techniques for seawater pre-treatment. The results of the use of several membrane types and methods of modification have also been discussed. The performance of composite membranes for seawater pre-treatment is defined and the future perspectives have been highlighted.

Materials in constructed wetlands for wastewater remediation: A review.

The wastewater treatment industry is constantly evolving to abate emerging contaminants and to meet stringent legislative requirements. The existing technologies need to be modified, or new innovative treatment techniques need to be developed to ensure environmental protection and secure sustainability in the future. Emphasis is mainly on nutrient recovery, energy-efficient systems, zero waste generation, and environmentally friendly techniques. Constructed wetlands (CWs) have evolved as natural, eco-friendly, economical, and low-maintenance alternatives for wastewater remediation. These wetlands employ several materials as adsorbents for the treatment, commonly known as media/substrate. This review paper presents an assessment of various materials that can be used as substrates in CWs for the efficient removal of organic and non-biodegradable pollutants in different types of wastewaters. The effect of pH, mineral composition, specific surface area, and porosity of various natural materials and agricultural and industrial wastes used as media in CWs for wastewater remediation was discussed. The study showed that different substrates like alum sludge, limestone, coal slags, rice husk, and sand had removal efficiency for chemical oxygen demand (COD): 71.8%-82%, total phosphorous (TP): 77%-80%, and total nitrogen (TN): 52%-82% for different types of wastewaters. It also highlights the challenges related to the long-term sustainability of these materials. PRACTITIONER POINTS: Physicochemical characteristics influence the removal efficiency of the materials Life of media is also important along with removal efficiency and cost The sustainability of materials is very crucial for the overall performance of the system.

Integrated textile effluent treatment method.

Textile wastewater purification is a challenging process. Conventional wastewater treatment methods either lack in efficiency, cost-effectiveness or leads to the generation of secondary pollutants. Additionally, some treatment methods are time-consuming. The research presented in the manuscript is a blend of filtration, biosorption, aeration, solar energy-assisted electrolytic precipitation, pH balance, and germicidal treatments with an aim of reducing the suspended solids, intense color, odor, pH, chemical oxygen demand (COD), total dissolved solids (TDS), electrical conductivity (EC), and heavy metal content of textile effluent. Use of environmentally sustainable surface activated biosorbents derived from waste weeds Water Hyacinth (WH) and Parthenium Hysterophorus (PH) as an alternative to commercial grade Activated Charcoal (AC), comparison of adsorption capacities of proposed adsorbents against AC for effluent decolorization, the application of solar energy to run an electrolytic precipitator, and the unique sequential design of various unit processes like coarse and fine filtration, biosorption, aeration, electrolytic precipitation, pH treatment and germicidal UV-C treatment to treat the effluent are some of the novel methodologies explored in the present study. The invented process provides almost completely decolorized (about 90%-94%), particle-free and odorless treated water, with the acceptable levels of heavy metals (Lead-not detected, Arsenic-not detected, Zinc-0.5-0.8 mg/L), TDS (1,500-1,850 mg/L), COD (149-169 mg/L) pH (7.1-7.15), and EC (2.5-2.8 mMhos/cm) as some of the important parameters, fitting well within the standard pollution limits. Performance efficiency estimation and statistical modeling were done for the data using the t test and f test. The values obtained were (t = 2.78 and f = 4.99 for treated WH against AC) and (t = 3.00 and f = 5.38 for treated PH against AC at 0.05 level of significance) as an essential part of the manuscript, proving the supremacy of the proposed process to achieve the standard pollution norms. Cost-effectiveness was an integral factor addressed in the proposed design, recorded a 1.7 USD per 1,000 L of input effluent, which was well below than most of the reported studies. The invented method in the present investigation thus provides an integrated, efficient, eco-friendly, and cost-effective solution to wastewater treatment. PRACTITIONER POINTS: Effluent decolorization is about 68% in comparison with conventional activated carbon. The adsorbent was found to be three times more active than activated carbon. COD value decreased from 2,352 mg/L to about 150 mg/L on treatment with the novel adsorbent.

Composites for wastewater purification: A review.

The review deals with different kinds of composites which have been used for wastewater treatment. The use of different types of composites ranging from nanocomposites, activated charcoal composites, polymer composites, oxide-based composites, hybrid composites, and biosorbent composites, etc. has been dealt with in detail, and presented as a central source of knowledge. The paper incorporates water purification explicitly via adsorption process, which has proven to be economical and efficient. These composites have been explored for treating or elimination of various hazardous substances like heavy metal species, different classes of colored contaminants (dyes), several organic and inorganic pollutants from wastewater. The composites discussed have successfully eliminated Zn2+, Ni2+, Cu2+, Pb2+, Hg, etc. In some instances the removal percentage of the contaminants was almost 100%. The presented data reveals the efficiency of composite materials in wastewater treatment over the conventional singular materials.

Kinetics studies on the adsorption of Methyl Orange and Metanil Yellow onto bottom ash: a comparative account.

The focal point of the study lies in the comparative evaluation of the kinetic data involved in the eradication of toxic dyes from waste waters using the adsorption technique. The investigation reveals the dynamic adsorption behavior of two hazardous textile dyes viz. Metanil Yellow and Methyl Orange over bottom ash, an industrial waste material. The impact of several experimental parameters has been inspected using batch mode to acquire information on the ongoing mechanism. The graphical profiles obtained for the adsorption of Metanil Yellow and Methyl Orange onto bottom ash suggested an increase in the adsorption rate with time, with gradual attainment of equilibrium between the adsorbing species and adsorbent. The study revealed that second-order kinetics has been followed in both cases. Adsorption of Methyl Orange over bottom ash followed particle diffusion whereas film diffusion predominated in the case of Metanil Yellow.

Study of decolorisation of binary dye mixture by response surface methodology.

Decolorisation of a complex mixture of two different classes of textile dyes Direct Red 81 (DR81) and Rhodamine B (RHB), simulating one of the most important condition in real textile effluent was investigated onto deoiled Argemone Mexicana seeds (A. Mexicana). The adsorption behaviour of DR81 and RHB dyes was simultaneously analyzed in the mixture using derivative spectrophotometric method. Central composite design (CCD) was employed for designing the experiments for this complex binary mixture where significance of important parameters and possible interactions were analyzed by response surface methodology (RSM). Maximum adsorption of DR81 and RHB by A. Mexicana was obtained at 53 °C after 63.33 min with 0.1 g of adsorbent and 8 × 10-6 M DR81, 12 × 10-6 M RHB with composite desirability of 0.99. The predicted values for percentage removal of dyes from the mixture were in good agreement with the experimental values with R2 > 96% for both the dyes. CCD superimposed RSM confirmed that presence of different dyes in a solution created a competition for the adsorbent sites and hence interaction of dyes was one of the most important factor to be studied to simulate the real effluent. The adsorbent showed remarkable adsorption capacities for both the dyes in the mixture.

Xanthium strumarium L. seed hull as a zero cost alternative for Rhodamine B dye removal.

Treatment of polluted water has been considered as one of the most important aspects in environmental sciences. Present study explores the decolorization potential of a low cost natural adsorbent Xanthium strumarium L. seed hull for the adsorption of a toxic xanthene dye, Rhodamine B (RHB). The characterization of the adsorbent revealed the presence of high amount of carbon, when exposed to Electron Dispersive Spectroscopy (EDS). Further appreciable decolorization took place which was confirmed by Fourier Transform Infrared Spectroscopy (FTIR) analysis noticing shift in peaks. Isothermal studies indicated multilayer adsorption following Freundlich isotherm. The rate of adsorption was supported by second order kinetics directing a chemical phenomenon during the process with dominance of film diffusion as the rate governing step. Moreover paper aims at correlating the chemical arena to the mathematical aspect providing an in-depth information of the studied treatment process. For proper assessment and validation of the observed data, experimental data has been statistically treated by applying different error functions namely, Chi-square test (χ2), Sum of absolute errors (EABS) and Normalized standard deviation (NSD). Further practical applicability of the low cost adsorbent was evaluated by continuous column mode studies with 72.2% of dye recovery. Xanthium strumarium L. proved to be environment friendly low cost natural adsorbent for decolorizing RHB from aquatic system.

Investigation of adsorption of Rhodamine B onto a natural adsorbent Argemone mexicana.

The present study aims at exploring the potential of the seeds of a tropical weed, Argemone mexicana (AM), for the removal of a toxic xanthene textile dye, Rhodamine B (RHB), from waste water. Impact of pH, adsorbent dosage, particle size, contact time and dye concentration have been assessed during adsorption. The weed has been well characterized by several latest techniques thereby providing an indepth information of the mechanism during adsorption. About 80% removal has been attained with 0.06 g of adsorbent over the studied system. Thermodynamic and kinetic studies, followed by second order kinetic model, directed towards the endothermic nature of adsorption. The results obtained from batch experiments were modelled using Langmuir and Freundlich isotherm and were analysed on the basis of R2 and six error functions for selection of appropriate model. Langmuir isotherm was found to be best fitted to the experimental data with high values of R2 and lower values of error functions. Adsorption study revealed the affinity of AM seeds for the dye ions present in waste water, introducing a novel adsorbent in field of waste water treatment.