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Amidst worsening water scarcity in the urban region, exploring alternative water sources is crucial. Atmospheric water extraction (AWE) technology emerges as a cost-effective and efficient remedy for the escalating issue of water scarcity. The objective of this research is to experimentally explore a novel AWE system that incorporates phase change material (PCM). This system is designed to facilitate uninterrupted water generation, even when there is no solar energy. It comprises of a solar air heater based on both-sides open evacuated tube collector having an area of 4.86 m2, which is encapsulated with acetamide-PCM. Additionally, it incorporates a silica gel filled desiccant bed and an air-cooled heat exchanger for vapor condensation. The system is investigated for two different desiccant bed weights of 15 kg (case 1) and 20 kg (case 2), respectively. The system's effectiveness is examined based on rate of adsorption, rate of regeneration, thermal, overall & exergy efficiency. The economic, environmental & enviro-economic analysis is also presented to ensure the system's sustainability & feasibility for its practical use. The results demonstrate that for case 2 the system extracts 4.1 L/day (0.843 L/m2/day) fresh water with 12.65%, 10.48% and 5.65% thermal, overall and exergy efficiency, respectively, for 20 kg desiccant bed weight. The fresh water cost is 0.12 $/L with 2 years & 1 month of payback time and 4 years & 7 months of energy payback period. The environmental & enviro-economic analysis ensures the system's eco-friendliness. Additionally, rigorous quality testing of the extracted water is carried out to affirm its suitability for safe consumption. • PCM encapsulated solar air heater for atmospheric water extraction. • Both sides open evacuated tube collector produces hot air of 130.10 °C. • Maximum water extracted is 4.1 L/day using air-cooled heat exchanger. • Thermal & exergy efficiency reported is 12.65 % & 5.65 %, respectively. • Water generation cost is 0.12 $/L, with system payback time of 2 years & 1 month. [ABSTRACT FROM AUTHOR]

Herein, we report the designing of a C3N4/BiOI heterostructure that is supported on gum acacia-crosslinked-poly(acrylamide) hydrogel to fabricate a novel nanocomposite hydrogel. The potential application of the obtained nanocomposite hydrogel to remediate crystal violet dye (CVD) in an aqueous solution was explored. The structural and functional analysis of the nanocomposite hydrogel was performed by FTIR (Fourier transform infrared spectroscopy), X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). The different reaction parameters, such as CVD concentration, nanocomposite hydrogel dosage, and working pH, were optimized. The C3N4/BiOI heterostructure of the nanocomposite hydrogel depicts Z-scheme as the potential photocatalytic mechanism for the photodegradation of CVD. The degradation of CVD was also specified in terms of COD and HR-MS analysis was carried to demonstrate the major degradation pathways. [ABSTRACT FROM AUTHOR]

• Atmospheric air to water generation using both end open evacuated tube collector. • Hot air temperature available from 5.07 m2 solar collector area is 140.9 °C. • 3.080 L/day of fresh water is produced by using an air-to-air condenser. • The system energy & exergy efficiency is 9.65% & 3.69%, respectively. • The cost of fresh water generation is 0.12 $/L, which is affordable. Regional economic, social, and ecological security are all entwined and influenced by the availability of water. Since the available water resources are depleting at a very faster rate and people are restricted to access the clean water, it is urgent to discover new & alternative sources of fresh water to meet everyone's requirements. An inexpensive and effective solution to the rising problem of the water shortage can be atmospheric air to water generation (AWG) technology. This study involves the development and experimental investigation of a novel AWG system based on adsorption under ambient conditions. Both end open evacuated tube collector solar air heater (ETC-SAH) with 5.07 m2 solar collector area and an air-to-air condenser is used. The system's performance is evaluated based on several key parameters, including adsorption & regeneration rate, energy & exergy efficiency, and economic analysis. The fresh water yield reported from the system is 3.08 L/day at 0.12 $/L cost. The energy & exergy efficiency reported by the system is 9.65% & 3.69%, respectively. Additionally, the water produced is subjected to testing at a regionally certified laboratory to confirm its safety for consumption. [ABSTRACT FROM AUTHOR]

Abstract Anionic surfactants are widely used as an effective chemical for enhanced oil recovery because of their unique characteristics of reducing interfacial tension (IFT) between the trapped crude oil and water, and alteration of wettability of reservoir rock from oil-wet to water-wet. However, the loss of surfactant by adsorption onto the solid rock surface is a major concern that reduces the efficiency of the surfactant flooding process and must be considered while designing the process. Present study highlights the equilibrium adsorption and kinetics of an anionic surfactant synthesized from soap-nut fruit on sandstone, carbonate and bentonite clay as representative of reservoir rocks. The mineralogy and morphology of the rocks were investigated by FE-SEM, XRD and BET surface area analysis. UV–Visible spectroscopy was used to measure the amount of surfactant adsorbed on solid rock/clay surface in batch experiments. The experimental equilibrium adsorption data were analyzed by using Langmuir, Freundlich, Temkin and Redlich-Peterson isotherm models and adsorption parameters were calculated. Adsorption kinetics of the surfactant system were studied and pseudo second order kinetic model was best fitted for the surfactant/rock/clay systems. Presence of salt was found to increase surfactant adsorption on rock/clay marginally. However, presence of alkali and nanoparticles was found to reduce the loss of surfactant by adsorption and shows synergistic effects on IFT reduction, which is beneficial for application of the surfactant in oil recovery. The findings of the study are quite helpful in proper designing of the surfactant flooding for enhanced oil recovery. Graphical abstract Image 1 Highlights • Mineralogical and morphological characterization of sandstone, carbonate, bentonite. • Effect of mineralogy, salt, pH, alkali, nanoparticles on adsorption of surfactant. • Modelling of Experimental data with various Isotherm Models. • Adsorption kinetic study along with mathematical fitting with kinetic equations. • Surfactant adsorption ability follow the trend bentonite > carbonate > sandstone. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Microwave synthesis of Gum Arabic- cl -poly(acrylamide) nanohydrogel. • Studied adsorptive removal of crystal violet dye onto nanohydrogel. • Good adsorption efficacy of 90.90 mg/g for crystal violet dye. • Adsorption process follows Langmuir isotherm. Abstract Natural biopolymers are better adsorbents due to better functionality, surface area, bio-compatibility and ease of procurement. The gum arabic in natural biopolymer derived from Acacia Arabic species. In the present work a novel nanohydrogel of gum arabic with acrylamide has been fabricated using microwave synthesis for adsorption of noxious crystal violet dye from aqueous medium. The prepared gum arabic-cl-poly(acrylamide) nanohydrogel (GA-cl-poly(AAm)) NHG was characterized by numerous techniques including SEM, XRD, TEM and FTIR. The GA-cl-poly(AAm) NHG showed promising adsorption ability for crystal violet dye. The effect of various adsorption factors such as concentration of GA-cl-poly(AAm) NHG and crystal violet, pH, temperature and time has been studied and reported. For understanding the adsorption mechanism three models Langmuir, Freundlich and Temkin were applied to adsorption data The kinetics and thermodynamics of adsorption were also investigated The adsorption capacity of crystal violet onto GA-cl-poly(AAm) NHG according to Langmuir model is found to be 90.90 mg/g. [ABSTRACT FROM AUTHOR]

The lack of fresh water, especially for the land-locked & arid regions, is becoming a significant barrier to the sustainable development of humanity. This has generated an urgent need to explore the solar-driven atmospheric water generation (S-AWG) technologies with high water yield. This research experimentally compares the performance of silica gel and molecular sieve on a novel S-AWG system. 25 kg of each desiccant material is used in a packed desiccant bed structure. In the nocturnal phase, adsorption is performed followed by regeneration during the day using hot air generated from evacuated tube solar air heater (ET-SAH). An air-to-air heat exchanger is employed for condensing the water vapors released in the process air after the desiccant bed regeneration. The water generated from silica gel is 1790 ml with energy & exergy efficiency of 23.14% & 10.43%, respectively. From the molecular sieve, 350 ml of water is generated with energy & exergy efficiency of 21.74% & 9.58%, respectively. The economic analysis of the system reveals that the cost of water generated from silica gel is 0.21 $/L, while from molecular sieve is 1.21 $/L. Water testing reports of the produced water using both the desiccant materials infers that it is drinkable. [Display omitted] • Solar atmospheric water generation (S-AWG) based on air-to-air heat exchanger. • Comparison of S-AWG system by using silica gel & molecular sieve. • 1790 ml/day water is produced from silica gel & 350 ml/day from molecular sieve. • Energy & exergy efficiency of the S-AWG system is 23.14% & 10.43%, respectively. • Water generated from silica gel costs 0.21 $/L. [ABSTRACT FROM AUTHOR]

Rapid increase in use of fungicides for the agricultural and industrial purposes has marked the deterioration of water resources which ultimately affects the human life. Accordingly, various attempts have been made in the removal of these noxious compounds. In the same context, we are presenting biopolymers based nanohydrogel sheets; guar gum- crosslinked -Soya lecithin nanohydrogel sheets (GG- crosslinked -SY NHS) used for the effective removal of a fungicide; thiophanate methyl from aqueous solution. Guar gum and soya lecithin were employed as the biopolymers in the fabrication of nanohydrogel sheets due to their non- toxic nature, easy availability, cheapness and significant properties. Due to the presence of highly reactive functional groups onto the surface of GG- crosslinked -SY NHS, good adsorption results have been obtained. Maximum adsorption capacity of 59.205 mg/g was observed with 20 mg GG- crosslinked -SY NHS and 25 ppm thiophanate methyl solution concentration as calculated from the Langmuir isotherm. Results showed that neutral pH favoured the adsorption process. Kinetics results were indicative of the physical interactions between the thiophanate methyl and GG- crosslinked -SY NHS surface. Thermodynamic results have shown the spontaneous and endothermic adsorption process. [ABSTRACT FROM AUTHOR]

In this research work we report synthesis of g-C 3 N 4 /FeVO 4 (CI) and g-C 3 N 4 /FeVO 4 /Fe@NH 2 -Biochar (CIB) nano-hetero assemblies for removal of methyl paraben (MeP) and 2-cholrophenol (2-CP) via adsorption, photocatalysis and photo-ozonation. CI and CIB have been characterized by FT-IR, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), scanning electron microscopy (SEM), UV–Vis spectroscopy, photoluminescence (PL), vibrating sample magnetometry (VSM), Brauner-Emmet Teller surface area analyzer (BET). CIB shows good photocatalytic activity owing to higher specific area, nanosheet porous structure, stability, broader solar spectrum response and reduced charge carriers recombination. Fe@NH 2 -biochar facilitates the degradation via high adsorption capability due to reduced recombination, better charge separation, adsorption and acting of biochar as sink of electrons. The CIB photocatalytic system was tested under three experimental conditions for photodegradation of MeP and 2-CP; adsorption followed by photo-degradation (AP); simultaneous adsorption and photocatalysis (SAP); SAP + O 3 . An apparent synergism between adsorption, photocatalysis and photo-ozonation brings out excellent and promising results. 98.4% of MeP and 90.7% of CP degradation was achieved under simultaneous adsorption and photocatalysis in presence of CIB. The results were analyzed in terms of reaction kinetics, adsorption isotherms, scavenger effect, liquid chromatography-mass spectrometry (LC-MS), Total Organic Carbon (TOC) analysis and cytotoxicity analysis of treated water. An efficient TOC removal 74.2 & 73.9% for MeP and 2-CP were respectively achieved under SAP + O 3 +CIB photocatalysis system. Degradation pathways have been proposed for degradation of MeP and CP thorough photo-degradation and photo-ozonation. The cyto-toxicity studies on Human peripheral blood lymphocytes provide a reference for removal of noxious pollutants in real systems. This experimental work paves a way to design tuneable simple junctions for photocatalytic applications by utilizing various experimental protocols. [ABSTRACT FROM AUTHOR]

In this research work we report Gum-ghatti supported ZnSe-WO 3 nano-hetero-assembly for solar powered degradation of endocrine disruptor Bisphenol S (BPA). The photocatalyst was characterized by Scanning electron microscopy (SEM), High resolution transmission electron microscopy (HRTEM), Small area electron diffraction (SAED), X-Ray diffraction (XRD), Fourier transform infra red spectroscopy (FTIR), Photoluminescence (PL), Energy dispersive X-ray (EDX), UV–vis spectrophotometry and Brauner Emmet Teller surface area analyzer (BET). We achieve a Z-scheme photocatalyst (ZnSe-WO 3 ) with a higher charge flow and visible absorption. Gum ghatti acts as a superadsorbent and a sink for charge carriers. The removal of BPA has been studied under three experimental protocols where 99.5% removal was achieved by symbiose of photocatalysis-adsorption-ozonation in just 45 min hetero-assembly has a high surface area, stability and reduced carrier recombination. The results have been analyzed by scavenger effect, mass spectrometry, kinetics and total organic carbon (TOC) analysis. 49.4% of TOC was removed and COD was reduced to 16.7% after 2 h in symbiotic condition. From the band edges and scavenger effect it was inferred that superoxide radical anions are major attacking species. The work paves way for designing of novel photocatalysts with increasing biogenic quotient and higher efficiency. [ABSTRACT FROM AUTHOR]

The pulp and paper industry consumes a huge amount of water and releases more polluted and colored wastewater every year. Many conventional techniques are used in the treatment of paper industry wastewater. However, for color removal from paper mill effluent, there is no proven method so far, on an industrial scale. Due to high energy input and high cost, there is an urgent need to find out a new technique that must be sustainable, economical, and environment friendly. Various methods have been investigated on bench scale and pilot scale also but no proven method for color removal on an industrial scale. The paper provides an overview of the color removal techniques from different sources of pulp and paper mill wastewater discharged by various industries. The review described various components involved in various processes for color removal from paper mill waste water. The present works focus on processes like chemical, chemical/physical, biological, physicochemical, and electrochemical applied in color removal from paper mill wastewater. The present review gives key information on the effectiveness, use, betterment, and limitations of numerous methods of treatment targeted at color removal from paper mill wastewater using various techniques still under evolution. • A critical study made on color removal from paper mill effluent using various methods. • Examined color removal efficiencies using conventional and advanced techniques. • Study on Cost analysis in color removal from paper mill effluent. • Future research suggestions described for better implementation of the processes. [ABSTRACT FROM AUTHOR]

Microplastics (MPs), as emerging pollutants, have attracted the attention of environmentalists, statespersons, and the scientific community over the last few decades. To address the spread of MPs in the environment, it is imperative to develop various removal techniques and materials that are effective, scalable, and ecologically benign. However, to the best of our knowledge, no review has systematically examined the removal of MPs using adsorption or provided an in-depth discussion on various adsorbents. Adsorption is an inexpensive and effective technology for wastewater treatment. Recently, many researchers have conducted studies on MP remediation using diverse adsorbent materials, such as biochar, activated carbon, sponges, carbon nanotubes, metal-layered oxides, metal-organic frameworks (MOFs), and zeolites. Each adsorbent has advantages and disadvantages. To overcome their disadvantages, researchers have been designing and developing hybrid adsorbents for MP remediation. This review provides insights into these individual adsorbents and also discusses hybrid adsorbents for MP removal. Finally, the review elaborates on future possibilities and ways to enable more efficient, scalable, and environmentally friendly MP cleanup. Overall, this review bridges the gap between contemporary MP remediation using adsorption techniques and adsorbent development. [Display omitted] • Adsorption-based microplastic remediation was reviewed. • The factors affecting microplastic adsorption were thoroughly discussed. • A comprehensive analysis is presented on several microplastic adsorbents. • Microplastic adsorption challenges and future perspectives are examined. [ABSTRACT FROM AUTHOR]

We report the fabrication of a novel waste-derived biochar-impregnated Bi 5 O 7 Br/Fe 3 O 4 (WBF) magnetic composite for photocatalytic removal of malachite green pollutant. The newly prepared catalyst was applied for the removal of malachite green dye under visible light irradiation. It was found that the composite degrades 99.39% MG dye within 20 min of the experiment as compared to Bi 5 O 7 Br, Fe 3 O 4, and biochar with 83.19%, 75.09%, and 55.47% in the 50-min experiment. The findings demonstrated that a photocatalytic integrated composite quickly transfers charges across surfaces and effectively separates electron-hole pairs, considerably increasing charge carrier separation and photocatalytic activity. Further, the kinetics show that the rate constant for WBF composite is 7.1 times higher than that observed for Bi 5 O 7 Br. Scavenging experiments reveal the huge role of.OH and •O 2 − radicals in malachite green degradation. Additionally, the magnetic nature of the catalyst ensures the easy separation of the catalyst during photocatlytic experiments and reduces the chance of secondary pollution. The results showed that integrating Bi 5 O 7 Br and biochar with Fe 3 O 4 to create photocatalytic composites is a very efficient strategy to boost photocatalytic activity for environmental waste water treatment. [Display omitted] • Newly designed waste derived bio-char impregnated Bi 5 O 7 Br/Fe 3 O 4 magnetic composite was successfully synthesised. • Composite degrades 99.39% MG dye within 20 min of the experiment. • Rate constant for MG removal for WBF composite is 7.1 times higher than that observed for Bi 5 O 7 Br. • Integrated composite improves the charge carrier separation and photocatalytic activity. • Composite exhibit sound stability upto six degradation cycles. [ABSTRACT FROM AUTHOR]

• AgO/MgO/FeO/Si 3 N 4 synthesized by microwave irradiation method. • Adsorption of tetracycline. • Maximum adsorption capacity of 172.41 mg/g. • Energy sites found to be energetically heterogeneous. Present study has been designed to govern the usage of nanocomposite of Si 3 N 4 with trimetallic oxide nanoparticles of Ag, Mg and Fe (AgO/MgO/FeO@Si 3 N 4) for the tetracycline (TC) removal from aqueous solution. Characterization techniques such as SEM, TEM, XRD, FTIR, XPS and BET were employed for analysing the successful fabrication of AgO/MgO/FeO@Si 3 N 4 nanocomposite. Adsorption process has been found to be dependent upon the surface properties of AgO/MgO/FeO@Si 3 N 4 nanocomposite (such as charge, functionality, etc), concentration of TC, solution pH and contact time. As determined from the isotherm studies, surface of AgO/MgO/FeO@Si 3 N 4 nanocomposite has been found to be energetically heterogeneous in nature as the data fitted well to Freundlich isotherm. Maximum adsorption capacity of AgO/MgO/FeO@Si 3 N 4 nanocomposite has been found to be 172.41 mg/g. Pseudo-second order kinetic model successfully explained the rate studies of TC adsorption. Also, reusability study of AgO/MgO/FeO@Si 3 N 4 nanocomposite has also been carried out. In short, the present study could determine an effective way for the removal of toxic pollutants from the wastewater system. [ABSTRACT FROM AUTHOR]

In the present work, a nanocomposite hydrogel is designed consisting of gum acacia, poly(acrylamide) and carbon nitride by facile microwave approach. This nanocomposite hydrogel is sensitive to environmental stimuli which is essential for its application in environmental remediation and as a drug delivery system. The effects of carbon nitride percentage and microwave Watt variation on swelling capacity of gum acacia‐cl‐poly(acrylamide)@carbon nitride (Ga‐cl‐PAM@C3N4) nanocomposite hydrogel are analyzed. The structural characterizations are considered by numerous techniques such as FTIR (Fourier transform infra‐red spectroscopy), X‐ray diffraction, transmission electron microscopy, scanning electron microscopy, and elemental mapping. Batch experiment is performed for remediation of ciprofloxacin (CIP) drug from water. Various parameters such as effect of ciprofloxacin doses, Ga‐cl‐PAM@C3N4 nanocomposite hydrogel dosage, pH, time and temperature for adsorption of CIP on gum acacia‐cl‐poly(acrylamide)@carbon nitride nanocomposite hydrogel is examined. Maximum adsorption capacity of Ga‐cl‐PAM@C3N4 nanocomposite hydrogel observed is 169.49 mg g−1 at pH 6.4. The drug loading and drug release capacity of Ga‐cl‐PAM@C3N4 nanocomposite hydrogel is investigated for ciprofloxacin. Drug release is monitored in artificial ocular solution (pH 8), saline (pH 5.5), acetate buffer (pH 2.2), and distilled water. Maximum drug release is observed in artificial ocular solution. [ABSTRACT FROM AUTHOR]

Pectin based quaternary amino anion exchanger (Pc-QAE) was prepared using simple crosslinking polymerization method. This anion exchanger was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). Pc-QAE was applied for the removal of phosphate anion from the aqueous solution. The adsorption process which was pH dependent showed maximum adsorption of phosphate anions at pH 7. Pc-QAE showed good monolayer adsorption capacity for phosphate anions which demonstrated its good capability towards Langmuir isotherm model. Moreover, the adsorption was evaluated thermodynamically and the negative value of Gibbs free energy (−1.791 KJ/mol) revealed the spontaneity of adsorption process. The value of ΔH° and ΔS° were found to be 15.28 and 49.48 KJ/mol, respectively representing the endothermic nature and enhancement in degree of freedom due to the adsorption process. [ABSTRACT FROM AUTHOR]

In this study, we have synthesized a starch/poly(alginic acid-cl-acrylamide) nanohydrogel (ST/PL(AA-c!-AAm) NHG) by co-polymerization method which was used as an effective adsorbent for the removal of coomassie brilliant (CB) blue R-250 dye from the aqueous solution. The synthesized nanohydrogel was characterized by FTIR, SEM and TEM techniques. The effect of initial dye concentration, temperature, and agitation time on the adsorption ability of the nanohydrogel was studied comprehensively. The experimental outcomes exhibited that the prepared nanohydrogel had high adsorption tendency to remove the CB from the aqueous solution. The regression coefficient values for Langmuir (0.99), Frendluich (0.93) and Tempkin (0.98) recommended that adsorption process fit to langmuir isotherm. The pseudo-second-order equation showed the better adsorption kinetics of the adsorption process. The feasibility of CB adsorption onto ST/PL(AA-cI-AAm) NHG was also studied thermodynamically and the results indicated that the adsorption was spontaneous and chemical in nature. [ABSTRACT FROM AUTHOR]

A polyaniline Zr(IV) selenotungstophosphate nanocomposite was prepared via sol-gel method and characterized by thermogravimetric analysis, scanning electron microscopy, energy dispersive X-ray spectroscopy, and transmission electron microscopy. The combined sorptional–photocatalytic activity of the nanocomposite for degradation of methylene blue and malachite green was investigated and was found to be more efficient than separate adsorption in the dark followed by photocatalysis. The dyes were degraded in 3 h by 96% and 89% by the combined process, as compared to 86% and 72% by the two-step process in 5 h. The nanocomposite material showed antimicrobial activity againstStaphylococcus aureusandEscherichia coli. [ABSTRACT FROM PUBLISHER]

In precedent work, nano-ZnO was supported on activated carbon or brick grain particles using simple co-precipitation method. Successful formation of ZnO-activated carbon (ZnO-AC) and ZnO-brick grain particle (ZnO-BGP) nanocomposites was ascertained by various spectral techniques. Scanning electron microscope (SEM) images revealed that ZnO particles were highly dispersed in activated carbon/brick grain particles. The size of ZnO-AC and ZnO-BGP was found to be 70 and 80 nm, respectively. Both ZnO-AC and ZnO-BGP exhibited excellent adsorption and photocatalytic activity for malachite green (MG) and congo red dye (CR) degradation. The adsorption data for MG and CR removal followed pseudo second order kinetic model. The adsorption capacity followed the order: ZnO-AC > ZnO-BGP > ZnO. The effect of adsorption on photocatalysis was explored under different reaction conditions. Simultaneous adsorption and photocatalysis (A + P) exhibited promoting effect on dye degradation. While adsorption followed by photocatalysis (A − P) had retarding effect on dye removal. ZnO-AC/A + P system emerged as highly efficient for MG and CR degradation. The rate of photodegradation followed pseudo first order kinetics. Using ZnO-AC/A + P system, 99 and 92% of COD removal was attainted for MG and CR degradation, respectively. The oxidative degradation mainly occurred through hydroxyl radicals. The prepared nanocomposites possessed higher recyclability and could be easily separated from solution by sedimentation. [ABSTRACT FROM AUTHOR]

Rapid industrial development is associated with high discharge of toxic pollutants into the environment. The industries discharge their wastewater containing organic pollutants directly into the water system without treating them that has posed many serious threats to environmental protection. The use of bioadsorbents for the removal of such toxic pollutants from the waste water due to its simple synthesis, easy operation, effectiveness, and economic viability have emerged a new dimension in the wastewater treatment approaches. Various adsorbents have been prepared to examine their adsorption capacity against different adsorbates, but, to attain sustainability, biocompatibility, and biodegradation, bio-adsorbents have been found to won the battle. Seaweed derived polysaccharide; Carrageenan (CR) has been proven to be an excellent adsorbent for the wastewater treatment. It has been successfully modified with various components to form CR based-magnetic composites, hydrogels, nanoparticle modified CR composites and many others to enrich and diversify its properties. In this review, we have explained the adsorption behaviour of various carrageenan based adsorbents for the removal of different dyes. The influence of various parameters such as the effect of initial concentration, adsorbent dosage, contact time, pH, temperature, and ion concentration on dye adsorption is well explained. This paper also summarizes the structure, morphology, swelling ability, and thermal stability of carrageenan. The data also expounds on the adsorption capacity, kinetic model, isotherm model, and nature of the adsorption process. Different types of solvents are used for the regeneration and reusability of carrageenan adsorbents and their regeneration studies and desorption efficiency is well-explained. The adsorption mechanism of dyes onto carrageenan based adsorbents has been well described in this review. This review provides a deep insight about the use of carrageenan based adsorbents for the wastewater treatment. [Display omitted] • A comprehensive review based on carrageenan or its various composites. • Carrageenan based adsorbents for removal of numerous pollutants were surveyed. • Various influential factors on the adsorption was taken into consideration. • Various categories of carrageenan were studied. [ABSTRACT FROM AUTHOR]

Polysaccharide-based hydrogels offer a great overlook for environmental applications and help in the elimination of various noxious pollutants from the water system. Novel carrageenan and itaconic acid-based superadsorbent hydrogel having appreciable swelling properties and adsorption capacity towards Methylene blue (MB), Crystal violet (CV), and Methyl Red (MR) was synthesized by suspension polymerization technique. The swelling study showed the dependency upon the temperature in which the swelling rate increased with increasing temperature with a maximum swelling rate of 417% at 318 K. For ascertaining the maximum adsorption capacity, various influential parameters such as contact time, adsorbent dose, dye concentration, and temperature were systematically studied. Maximum adsorption capacity as calculated from the Langmuir isotherm was 2439.02, 1111.11, and 666.68 mg/g for MB, CV, and MR, respectively. Thermodynamic studies revealed the spontaneous nature of the undertaken dye adsorption experiment. Overall, the present study reveals that the synthesized superadsorbent hydrogel can be used as an efficient adsorbent for the removal of dyes from an aqueous solution. [Display omitted] • Superadsorbent hydrogel designed for the adsorptive removal of cationic dyes. • Maximum adsorption capacity obtained for MB followed by CV and MR. • Results have been analyzed by isotherm and kinetic studies. • Superadsorbent hydrogel successfully recycled for consecutive 5 cycles. [ABSTRACT FROM AUTHOR]

[Display omitted] • porous Zn/Fe LDH exhibited appreciable adsorption capacity. • Successful decomposition of H 2 O 2 present between the LDH layers. • Introduction of pores in the layers enhanced the surface area and adsorption activity. • Successfully reusable for consecutive 6 cycles adsorption cycles. Present work include the designing of a novel porous Zn/Fe layered double hydroxide (LDH) based adsorbent using a combination of three methods, namely, co-precipitation, hydrothermal, and thermal treatment. The Zn/Fe LDH was synthesized by co-precipitation followed by hydrothermal method. The LDH was then intercalated with H 2 O 2 and its decomposition under the thermal treatment created oxygen bubbles that pierce holes in the layered structure of the LDH by local pressure build-up. Major techniques used for assessing the morphology and surface area characteristics of the LDH and porous LDH were Scanning electron microscope (SEM) and Brunauer-Emmet-Teller (BET). The intercalation of H 2 O 2 and its later decomposition triggered by thermal treatment lead to the introduction of pores in the LDH layers that increased the surface area from 108.863 m2/g to 168.923 m2/g. The synthesized adsorbent was utilized for the removal of an antibiotic; ciprofloxacin (CIP) from the aqueous solution. The porous Zn/Fe LDH adsorbent was featured with an admirable CIP adsorption capacity of 344.83 mg/g at pH 6.5 and temperature 298 K. The adsorption of CIP onto porous Zn/Fe LDH adsorbent followed the Freundlich isotherm model and pseudo-second-order kinetic model. The temperature increase negatively affected the adsorption rate. The adsorption mechanism of CIP onto porous Zn/Fe LDH was also projected and established, and Cπ- metal interactions, hydrogen bonding, and electrostatic interactions, were found to be the major interactive forces. The thermodynamic study revealed the exothermic and spontaneous nature of the adsorption experiments. Overall, the synthesized adsorbent is sustainable in terms of its usability and non-toxic nature. [ABSTRACT FROM AUTHOR]

In pharmacy, semisynthetic antibiotics with beta-lactam ring are the most prominently used drugs. The use of these drugs for humans and animals is continuously expanding. Their presence in the water system even at low concentrations can prove to be fatal to living beings. Also, they can even grow antibiotic-resistant bacteria and thus elimination of such drugs becomes very essential. Our study is focused on batch experiments for adsorptive removal of ampicillin (AMP) and its cumulative release in different solutions using xanthan gum-cl-poly(itaconic acid)/bentonite (XG- cl -poly(IA)/BN) nanocomposite hydrogel. It was synthesized by facile microwave method. The adsorption data of AMP was analyzed using various isotherm models such as Langmuir, Freundlich, Temkin and kinetic models such as Pseudo-first order, Pseudo-second order and Intraparticle diffusion. The maximum adsorption capacity as determined from Langmuir model was 245.09 mg/g at 318 K and solution pH 7. Also, XG- cl -poly(IA)/BN nanocomposite hydrogel was evaluated for AMP release in distilled water and at different pH solutions (2.2, 5.4, 7.4 and 9.4). The maximum AMP release was observed at pH 2.2 (37%). Unlabelled Image • A novel XG- cl -poly(IA)/BN nanocomposite hydrogel was synthesized. • The maximum adsorption capacity for ampicillin was found out to be 245 mg/g. • Adsorption data correlated by isotherm models: Langmuir, Freundlich and Tempkin. • XG- cl -poly(IA)/BN nanocomposite hydrogel was evaluated for ampicillin release. • Maximum ampicillin release was observed at pH 2.2 (37%). [ABSTRACT FROM AUTHOR]

• Atrazine removal using chitin based nanohydrogel- adsorption & desorption. • Chitin- cl -poly(acrylamide-co-itaconic acid) - microwave synthesis. • Results shows the maximum adsorption capacity of 204.08 mg/g. • Chitin- cl -poly(acrylamide-co-itaconic acid) nanohydrogel - pH responsive nature. Removal of commonly used pesticide, atrazine was examined by employing chitin based nanohydrogel. Chitin- cl -poly (acrylamide-co-itaconic acid) nanohydrogel was synthesized by microwave method. Dissolution of chitin was done by freezing thawing method in NaOH/urea solution. The morphology and functional characteristics were confirmed by FTIR, XRD, SEM, TGA, TEM, and EDX techniques. Maximum swelling capacity, isotherm study, kinetics, adsorption and desorption of atrazine pesticide were evaluated in this study. Maximum adsorption capacity of designed nanohydrogel was found to be 204.08 mg/g. Langmuir and pseudo- second order models were determined to be applicable for explaining the undertaken adsorption process. Neutral pH was found to be favorable for maximum adsorption. In addition, results have specified the pH responsive nature of nanohydrogel for controlled release of atrazine. [ABSTRACT FROM AUTHOR]

Nanocomposite hydrogels are polymeric networks that possess a unique property of hydration. The presence of alcohols, carboxylic acids and amides as hydrophilic moieties in structure of nanocomposite hydrogels enhances their stiffness and water-absorbing capacity. Addition of cross-linker in the synthesis of hydrogels increases their stability under extreme conditions of temperature, pH and pressure. Natural polymer-based nanocomposite hydrogels are biodegradable, highly hydrophilic and possess good mechanical strength. Gelatin, chitin, cellulose, pectin, carrageenan, starch and alginate are natural polymers commonly used to fabricate nanocomposite hydrogels. Nanocomposite hydrogels have special characteristics such as high swelling rate, selectivity and stimuli-sensitive nature. Here we review nanocomposite hydrogels for environmental protection and biomedical engineering. Applications in biomedical engineering include drug delivery agents, wound dressing, tissue engineering and antibacterials. Applications in environmental protection include ion exchangers, adsorption, photocatalysis and soil conditioning. Many nanocomposite hydrogels show excellent adsorption selectivity for heavy metal ions: Cu2+ up to 30.35 mg/g, Pb2+ up to 35.94 mg/g, and Zn2+ and Fe3+ up to 94.34 mg/g. Xanthan gum-based nanocomposite hydrogel has removed 96% dye from industrial effluent as reported. In addition, most of the nanocomposite hydrogels showed better adsorption capacity for pollutants in the pH range from 5 to 7. The nanocomposite hydrogels could also be regenerated and successfully utilized for several times. Nanocomposite hydrogels are therefore good bio-absorbent materials for environmental detoxification. [ABSTRACT FROM AUTHOR]

Fluoride contamination of groundwater is a serious problem in several countries of the world because of the intake of excessive fluoride caused by the drinking of the contaminated groundwater. Geological and anthropogenic factors are responsible for the contamination of groundwater with fluoride. Excess amounts of fluoride in potable water may cause irreversible demineralisation of bone and tooth tissues, a condition called fluorosis, and long-term damage to the brain, liver, thyroid, and kidney. There has long been a need for fluoride removal from potable water to make it safe for human use. From among several defluoridation technologies, adsorption is the technology most commonly used due to its cost-effectiveness, ease of operation, and simple physical process. In this paper, the adsorption capacities and fluoride removal efficiencies of different types of adsorbents are compiled from relevant published data available in the literature and represented graphically. The most promising adsorbents tested so far from each category of adsorbents are also highlighted. There is still a need to discover the actual feasibility of usage of adsorbents in the field on a commercial scale and to define the reusability of adsorbents to reduce cost and the waste produced from the adsorption process. The present paper reviews the currently available methods and emerging approaches for defluoridation of water. [ABSTRACT FROM AUTHOR]

Currently, the photocatalytic nanomaterials performing under solar radiation have gained worldwide attentions due to increasing environmental deterioration. For utilizing the sunlight for degradation of emerging pollutants it is important to develop visible active photocatalysts. This laboratory scale work reports magnetic and optically active nano-photocatalyst Fe x Zn 1−x O(x = 0.01, 0.03, 0.05) synthesized by solution combustion method. High resolution transmission microscopy suggests a slight degradation in the crystallite structure with Fe doping. X-ray photoelectron spectroscopy analysis shows the presence of intrinsic defects in the crystal structure. Zn resides in +2 and and Fe in +3 oxidation state. Optical band gap studies were made with band structure for each doped sample. The photoctalytic activity of the samples was tested by solar degradation of noxious pollutant Bisphenol A. 99.1% of bisphenol was degraded in 90min in presence of Fe 0.03 Zn 0.97 O under synergistic adsorption and photocatalysis. The results were analyzed in terms of total organic carbon, chemical oxygen demand, effect of scavengers, gas chromatography-mass spectrometry and reusability. In presence of Fe 0.03 Zn 0.97 O, 45.3% of total organic carbon was removed and chemical oxygen demand was reduced to 11.2%. A possible mechanism with structures of the intermediates has been given. Effect of scavengers reveal that hydroxyl radicals are major reactive oxygen species involved which is also supported by the band edge positions. The research work promises to design highly photo-active tuneable magnetic photocatalysts for solar powered degradation of contaminants of emerging concern with a simple and cost-effective approach. [ABSTRACT FROM AUTHOR]

Sodium dodecyl sulphate-ironsilicophosphate (SDS-FeSP) nanocomposite has been fabricated by using co-precipitation method. The resultant SDS-FeSP nanocomposite showed excellent ion exchange capacity, high stability and selectivity towards specific metal ions. The characterization of SDS-FeSP nanocomposite was carried out by using modern techniques including TEM, SEM-EDX and FTIR. SDS-FeSP had higher ion exchange capacity (1.45 meq/g) in comparison to its inorganic counterpart FeSP (0.40 meq/g). The physicochemical properties such as pH titrations, elution behavior and thermal stability of SDS-FeSP were examined to find their relation in the context of enhanced ion exchange capacity. The sorption studies for several alkaline and heavy metals were performed in two different eluents. The studies revealed marked selectivity of SDS-FeSP nanocomposite towards Zn 2+ and Mg 2+ metal ions. Hence, analytical utility of SDS-FeSP nanocomposite was accomplished by performing some binary separations as well as quantitative separation of Mg 2+ metal ion from a real sample (Digene) on the column packed with the synthesized SDS-FeSP. [ABSTRACT FROM AUTHOR]

In this study, chitosan- crosslinked -poly (alginic acid) nanohydrogel ( CN-cl-PL(AA) NHG) was synthesized by co-polymerization method. It was used an effective adsorbent for the exclusion of Cr(VI) metal ion from aqueous medium. The synthesized nanohydrogel was characterized by FTIR, SEM and TEM. The TEM images clearly indicated the appearance of smooth surface with average size of particles ranging from 30 to 80 nm. The effect of different adsorption parameters like agitation time, temperature, initial metal ion concentration and adsorbent dosage was studied and optimized. The results demonstrated that the prepared chitosan- crosslinked -poly (alginic acid) nanohydrogel had high adsorption tendency for the removal of Cr(VI) from the aqueous solution. The pseudo-second-order equation represented the better adsorption kinetics for the adsorption process. The thermodynamic studies showed the adsorption of Cr(VI) onto CN-cl-PL(AA) NHG was spontaneous and chemical in nature. [ABSTRACT FROM AUTHOR]

Highlights: [•] A novel nanocomposite Fe0.01Ni0.01Zn0.98O/polyacrylamide was synthesized. [•] FNZP/PAM nanocomposite shows good degradation efficiency for MB and MG. [•] Rapid decolouration of dyes was observed under coupled adsorption and photocatalysis. [•] Dye degradation followed the pseudo first-order kinetics. [•] A higher recycle efficiency and antibacterial activity was achieved for nanocomposite. [Copyright &y& Elsevier]

Highlights: [•] Guar gum–cerium (IV) tungstate nanocomposite (GG/CTNC) was prepared. [•] The ion exchange capacity of GG/CTNC was investigated. [•] The exchanger was highly selective for leads ions. [•] GG/CTNC proved to be an efficient adsorbent for cationic dye. [•] The dye removal followed pseudo second order kinetics. [ABSTRACT FROM AUTHOR]

The water resources contamination in an alarming concern for sustainable environment. This has led to development of new technologies and materials for waste water detoxification. In the present study, we have fabricated novel trimetallic based mixed oxides decorated reduced graphene oxide (rGO) composite using facile microwave method and utilized it as an adsorbent for the removal of congo red dye from aqueous solution. The final composite showed highly agglomerated metal oxides present on the rGO surface. The high surface area and activity of the synthesized adsorbent resulted in its high adsorption capacity of 333.32 mg/g for congo red. The Langmuir model better explained the isotherm data indicating the monolayer adsorption of congo red molecules onto Ag 2 O–Al 2 O 3 –ZrO 2 /rGO surface. The grander adsorption ability of Ag 2 O–Al 2 O 3 –ZrO 2 /rGO towards organic dye indicate its probable utilization in the removal of other dyes also from wastewater. • Trimetallic oxides decorated into rGO matrix were synthesized. • Adsorption of congo red from aqueous solution was investigated. • Maximum adsorption capacity of 333.32 mg/g was obtained using Langmuir isotherm. • Langmuir model better explained the adsorption isotherm data and mechanism. [ABSTRACT FROM AUTHOR]