Potential of Moringa Oleifera Seed as a Natural Adsorbent for Wastewater Treatment

The present study deals with the appropriateness of the coagulation process using natural coagulant Moringa oleifera seed. Natural coagulants are useful for the treatment of wastewater because of its sustainability, cost-effectiveness, non-toxicity and lesser quantity of sludge formation. M. oleifera seed having a chemical composition of polypeptides having 6 amino acids like arginine acid, methionine acid, glutamic acid, phenylalanine, threonine, and histidine. M. oleifera is also known as a cationic polyelectrolyte and having molecular weight 6,000 to16,000 Dalton. The main objective of research work is the application of the M. oleifera seed as a natural adsorbent to treat synthetic dairy wastewater. The effects of pH, agitation time, the dose of sorbent and efficacy of M. oleifera seeds kernel for turbidity removal was assessed. M. oleifera seed eliminates turbidity 95 % and colour 94 % using 0.22 gm pod powder, and 0.2 L of 1.0 g/L synthetic dairy wastewater. Naturally dried M. oleifera seeds remove turbidity 95 %, sundried seeds remove turbidity 52 % and oven-dried seeds 45 %. As naturally dried M. oleifera pod having more surface area for adsorption and inter-particulate bridging which extract the extra active ingredients. pH range between 5 and 8 is more suitable to degrade the turbidity and colour. It is concluded that in the presence of an aqueous soluble cationic coagulant protein has great potential to remove the turbidity and colour of wastewater. HIGHLIGHTS oleifera seed having a chemical composition of polypeptides having 6 amino acids like arginine acid, methionine acid, glutamic acid, phenylalanine, threonine, and histidine oleifera seeds consist of crude fiber, lignin, hemicellulose, and cellulose. It also contains amino functional groups (R-NH3), carboxyl group (C=O), and fiber carbonaceous. The functional group present in M. oleifera seeds is dissociated during the adsorption process at various pH oleifera has good property of coagulation-flocculation (C-F) The effectiveness of naturally dried seed kernel is more effective than other seed kernels GRAPHICAL ABSTRACT

Potentiometric back titration as a robust and simple method for specific surface area estimation of lignocellulosic fibers

The specific surface area (SSA) of cellulosic or lignocellulosic fibers is seldom reported in the recent literature on papermaking, despite its close relation with the degree of refining and other key pulp properties. Amidst outdated assays (Pulmac permeability test) and methods that, while accurate, are of doubtful usefulness for papermaking purposes (N2 adsorption–desorption), we suggest a methodology based on the cationic demand. A commonly used cationic polyelectrolyte, poly(diallyldimethylammonium chloride) (PDADMAC), became adsorbed onto thermomechanical pulp samples. Then, a potentiometric back titration with an anionic polyelectrolyte measured the cationic demand, expressed as microequivalents of PDADMAC per gram of pulp. Multiplying this value by the surface area of a microequivalent of polymer, considering rod-like conformation in the case of minimum ionic strength, yielded the SSA of the lignocellulosic pulp. Our system assumes that the quaternary ammonium groups were anchored through electrostatic and ion–dipole interactions. Measuring the carboxyl content allowed for discriminating between both kinds of forces. Finally, the model could be validated by plotting the estimated SSA values against the Schopper-Riegler degree, attaining high correlation coefficients (R2 ~ 0.98). Owing to the high molecular weight of the polyelectrolyte of choice (107 kDa), and more particularly in the case of fine-free pulps, SSA values estimated from the cationic demand were consistently lower than those from dye (Congo red) sorption. Instead of being a drawback, the limited diffusion of PDADMAC through fibers can enable papermakers to attain a more helpful quantification of the available surfaces in operations with low residence times.

Layer-by-layer self-assembly preparation and desalination performance of graphene oxide membrane

Unlike previous utilization of ultrafiltration membranes as supporters of graphene oxide (GO) composite membranes, this study first adopts microporous nylon membranes as substrates. The cationic polyelectrolyte/GO composite membranes are prepared by the layer-by-layer self-assembly method via electrostatic attraction. The introduction of polycations between nanochannels in the GO membranes effectively suppresses the swelling and improves the stability of the membranes. It is found that the polyelectrolytes' charge density and the surface potential of the composite membranes jointly determine the membranes' properties. The experimental results show that the novel GO membranes can obtain high flux and considerable desalination performance under low operating pressure. Typically, the salt rejection rate reaches 66.8% for 1.0 g/L MgSO4, and the flux is 39.8 L·m−2·h−1·bar−1. Benefitting from the GO composite membranes keeping similar retention for both high and low concentration salt solutions, the ideal desalination performance could be obtained through multi-stage processes on the premise of ensuring high flux, which is more suitable for industry.

A salt-free, zero-discharge and dyebath-recyclable circular coloration technology based on cationic polyelectrolyte complex for cotton fabric dyeing

Textile industry is one of the most polluting industries due to the large quantities of dyeing wastewater it generates and discharges. Herein, we report an eco-friendly and sustainable circular coloration technology based on cationic polyelectrolyte complex to realise salt-free, zero-effluent-discharge circular dyeing for cotton fabrics with a recyclable dyebath by using a typical cationic polyelectrolyte polyhexamethylene biguanide (PHMB) bonded with anionic dyes. The cotton fabrics were first treated with PHMB and then dyed with three commercial acid dyes. Colour measurements show that the colour strength is controllable by adjustment of concentrations of both PHMB and the dyebath. The dyed fabric samples were found to have good/excellent colour levelness (< 0.49), and the colour fastness (Grade 3 ~ 5) was basically satisfactory and acceptable. The dyebath was proved to be recyclable for circular dyeing occurring at room temperature, which greatly reduces consumption of both water and heat energy for textile dyeing. Meanwhile, the dyed fabrics showed antimicrobial activity, particularly for the gram-positive S. aureus, which may help reduce the healthcare-associated infections that transmit through textiles. These results suggest that cationic polyelectrolyte-based circular dyeing could provide a promising and practicable strategy to address the pollution issue caused by wastewater generated in dyeing process in the textile industry.