Innovative treatment of industrial effluents through combining ferric iron and attapulgite application.

The escalation of industrial activities has escalated the production of pharmaceutical and dyeing effluents, raising significant environmental issues. In this investigation, a hybrid approach of Fenton-like reactions and adsorption was used for deep treatment of these effluents, focusing on effects of variables like hydrogen peroxide concentration, catalyst type, pH, reaction duration, temperature, and adsorbent quantity on treatment effectiveness, and the efficacy of acid-modified attapulgite (AMATP) and ferric iron (Fe(III))-loaded AMATP (Fe(III)-AMATP) was examined. Optimal operational conditions were determined, and the possibility of reusing the catalysts was explored. Employing Fe3O4 as a heterogeneous catalyst and AMATP for adsorption, CODCr was reduced by 78.38-79.14%, total nitrogen by 71.53-77.43%, and phosphorus by 97.74-98.10% in pharmaceutical effluents. Similarly, for dyeing effluents, Fe(III)-AMATP achieved 79.87-80.94% CODCr, 68.59-70.93% total nitrogen, and 79.31-83.33% phosphorus reduction. Regeneration experiments revealed that Fe3O4 maintained 59.48% efficiency over three cycles, and Fe(III)-AMATP maintained 62.47% efficiency over four cycles. This work offers an economical, hybrid approach for effective pharmaceutical and dyeing effluent treatment, with broad application potential.

Efficient oil-water emulsion treatment via novel composite membranes fabricated by CaCO3-based biomineralization and TA-Ti(IV) coating strategy.

Continuous increasing discharge of industrial oily wastewater and frequent occurrence of oil spill accidents have taken heavy tolls on global environment and human health. Organic-inorganic modifications can fabricate superhydrophilic/submerged superoleophobic membranes for efficient oil-water separation/treatment though they still suffer from complex operation, non-environmental friendliness, expensive cost or uneven distribution. Herein, a new strategy regarding tannic acid (TA)-Ti(IV) coating and CaCO3-based biomineralization through simple inkjet printing processes was proposed to modify polyvinylidene fluoride (PVDF) membrane, endowing the membrane with high hydrophilicity (water contact angle (WCA) decreased from 86.01° to 14.94°) and underwater superoleophobicity (underwater contact angle (UOCA) > 155°). The optimized TA-Ti(IV)-CaCO3 modified membrane possessed perfect water permeation to various oil/water emulsions (e.g., 355.7 L·m-2·h-1 for gasoline emulsion) under gravity with superior separation efficiency (>98.8 %), leading the way in oil/water emulsion separation performance of PVDF membranes modified with polyphenolic surfaces to our knowledge. Moreover, the modified membrane displayed rather high flux recovery after eight cycles of filtration while maintaining the original excellent separation efficiency. The modification process proposed in this study is almost independent of the nature of the substrate, and meets the demand for simple, inexpensive, rapid preparation of highly hydrophilic antifouling membranes, showing abroad application prospect for oil-water emulsion separation/treatment.

Mechanistic insights into Ca-alginate gel-associated membrane fouling affected by ethylene diamine tetraacetic acid (EDTA).

While transparent exopolymer particles (TEP) is a major foulant, and ethylene diamine tetraacetic acid (EDTA) is a strong chelating agent frequently used for fouling mitigation in membrane-based water treatment processes, little has been known about TEP-associated membrane fouling affected by EDTA. This work was performed to investigate roles of EDTA addition in TEP (Ca-alginate gel was used as a TEP model) associated fouling. It was interestingly found that, TEP had rather high specific filtration resistance (SFR) of 2.49 × 1015 m-1·kg-1, and SFR of TEP solution firstly decreased and then increased rapidly with EDTA concentration increase (0-1 mM). A series of characterizations suggested that EDTA took roles in SFR of TEP solution by means of changing TEP microstructure. The rather high SFR of TEP layer can be attributed to the big chemical potential gap during filtration described by the extended Flory-Huggins lattice theory. Initial EDTA addition disintegrated TEP structure by EDTA chelating calcium in TEP, inducing reduced SFR. Continuous EDTA addition decreased solution pH, resulting into no effective chelating and accumulation of EDTA on membrane surface, increasing SFR. It was suggested that factors increasing homogeneity of TEP gel will increase SFR, and vice versa. This study revealed the thermodynamic mechanism of TEP fouling behaviors affected by EDTA, and also demonstrated the importance of EDTA dosage and pH adjustment for TEP-associated fouling control.

Surface modification of polyvinylidene fluoride (PVDF) membrane via radiation grafting: novel mechanisms underlying the interesting enhanced membrane performance.

This study provided the first attempt of grafting hydrophobic polyvinylidene fluoride (PVDF) membrane with hydrophilic hydroxyethyl acrylate (HEA) monomer via a radiation grafting method. This grafted membrane showed an enhanced hydrophilicity (10° decrease of water contact angle), water content ratio, settling ability and wettability compared to the control membrane. Interestingly, filtration tests showed an improved dependence of water flux of the grafted membrane on the solution pH in the acidic stage. Atomic force microscopy (AFM) analysis provided in-situ evidence that the reduced surface pore size of the grafted membrane with the solution pH governed such a dependence. It was proposed that, the reduced surface pore size was caused by the swelling of the grafted chain matrix, with the pH increase due to the chemical potential change. It was found that the grafted membrane showed a lower relative flux decreasing rate than the control membrane. Moreover, flux of the bovine serum albumin (BSA) solution was noticeably larger than that of pure water for the grafted membrane. Higher BSA flux than water flux can be explained by the effects of electric double layer compression on the polymeric swelling. This study not only provided a pH-sensitive PVDF membrane potentially useful for various applications, but also proposed novel mechanisms underlying the enhanced performance of the grafted membrane.