Carboxymethyl chitosan (CMCS), acrylamide, and methacryloxyethyltrimethyl ammonium chloride were used as co-monomers to produce a sludge dewatering agent carboxymethyl chitosan-graft-poly(acrylamide-methacryloxyethyltrimethyl ammonium chloride) (CCPAD) by UV-induced graft polymerization. Single-factor experiments and response surface methodology were employed to investigate and optimize the grafting rate, grafting efficiency, and intrinsic viscosity influenced by the total monomer concentration, CMCS concentration, cationic degree, pH value, and illumination time. The structure, surface morphology, and thermal stability of CCPAD were characterized by infrared spectroscopy, hydrogen nuclear magnetic resonance, X-ray diffraction, scanning electron microscopy, and differential thermal-thermogravimetry. The raw sludge with 97.9% water content was sourced from the concentrated tank of a sewage treatment plant and used in the sludge condition experiments. In addition, CCPAD was applied as the sludge conditioner to investigate the effects of cationic degree, intrinsic viscosity, and pH on the supernatant turbidity, moisture content, specific resistance to filtration, and sludge settling ratio. Moreover, the mechanism of sludge conditioning by CCPAD was discussed by examining the zeta potential and extracellular polymeric substance (EPS) content of the supernatant. The sludge dewatering results confirmed that CCPAD had excellent performance for improving sludge dewaterability.

In this study, the combination of Fenton's reagent and cationic polyacrylamide (CPAM) was used in sludge conditioning for the enhancement of sludge dewatering performance. The effects of CPAM, H2O2, and Fe2+ dosages and pH on the moisture content (MC) of the filter cake, the specific resistance of filtration (SRF), and the residual turbidity of the supernatant (RT) were investigated. To observe influencing mechanisms of sludge dewatering further, optical microscopy and scanning electron microscopy (SEM) were employed. Results demonstrated that the sludge dewatering performance obtained by the combination of Fenton's reagent and CPAM was significantly better than that obtained using Fenton's reagent or CPAM alone. The optimum conditions of sludge conditioning were as follows: 400 mg · L−1 Fe2+, 4 g · L−1 H2O2, 40 mg · L−1 CPAM, and pH 4. The SRF, MC, and RT at optimum conditions were reduced to minimum values of 1.06 × 1012 m/kg, 58.9 %, and 3.7, respectively. The optical microscopy and SEM analyses of sludge flocs confirmed that they were more conducive to sludge dewatering after the combination of Fenton oxidation and flocculation. The sludge dewatering results demonstrated that the combination of Fenton and flocculation process exhibited excellent performance in enhancing sludge dewatering and is a promising pretreatment approach to sludge disposal.

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In this work, a new cationic flocculant, CMCTS-g-CPAM was synthesized by acrylamide (AM), methacryloyloxyethyltrimethylammonium chloride (DMC) and carboxymethyl chitosan (CMCTS) through UV initiated graft polymerization techniques. The structure of CMCTS-g-CPAM was analysed by infrared spectroscopy (IR), nuclear magnetic resonance spectroscopy (1 H NMR) and X-ray diffraction (XRD) techniques which indicates that AM and DMC are grafted successfully onto CMCTS to obtain CMCTS-g-CPAM. The potential of CMCTS-g-CPAM for the sludge dewatering was investigated. The effects of cationic degree, intrinsic viscosity, dosage and pH on the sludge dewatering performance were studied. The results indicate that the optimal dewatering performance with minimum supernatant turbidity of 5.40 NTU, the moisture content of the filter cake of 79.28% and the specific resistance of the sludge of 1.96 × 10 13 m/kg was obtained at 30 mg/L CMCTS-g-CPAM at pH 9-10. Finally, from the microscopic and electron micrographs investigation, it was confirmed that the particle size of the CMCTS-g-CPAM treated sludge was significantly large to enhance hydrophobicity and improve dewatering performance.

Introduction The diabetic macular edema (DME) is a relevant cause of visual impairment in diabetes. The current treatments are limited by high costs, risk of infections and damage to retinal cells. Randomized controlled studies (RCTs) have investigated oral traditional Chinese medicines (TCMs) for the treatment of DME. We aimed at determining the efficacy and safety of oral TCMs by systematically reviewing the full set of studies. Methods and analysis Published RCTs will be searched through 12 databases until October 1, 2022. Two investigators will conduct independent literature search, data extraction and assessment of quality. The risk of bias will be judged with the version 2 of the Cochrane risk-of-bias tool. The RevMan software will be utilized to analyze data. Dichotomous data will be assessed by using odds ratios and 95% confidence intervals (CIs). We will evaluate continuous data by using weighted mean differences and 95% CIs. We are going to assess heterogeneity by Cochran's Q test and the I2 statistics. We plan sensitivity analysis and subgroup analysis to identify sources of heterogeneity. Funnel plots, Egger's tests and Begg's tests will be also performed.