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 Nowadays, according to membrane-based filtration processes; the use of substances such as antiscalants that prevents the formation of deposits during the treatment process, is very important from industrial point of view. This study aimed to synthesize styrene-maleic anhydride copolymer (PSMA) using the radical polymerization method and to investigate the factors and parameters affecting its use in reverse osmosis membrane for removal of TDS from the Persian Gulf water sample.

 The present study was performed in laboratory scale to investigate the efficiency of synthetic antiscalants, in batch and fundamental-applied forms, as well as on a semi-industrial scale using reverse osmosis (RO) membrane system. Then, to evaluate its performance on the electrical conductivity (EC), total dissolved solids (TDS), flow flux, and membrane fouling in the reverse osmosis system, the effect of parameters such as pH and antiscalant concentration on increasing membrane efficiency and effectiveness were investigated.

 The results showed that by adding antiscalant to the reverse osmosis system, the EC and TDS of the sample can be reduced in the range of 99.5-8.98% and 97.98-2.7%, respectively, so that in the study period, which was 1 hour, less performance reduction was observed in reverse osmosis membranes than in the absence of antiscalant. Also, the concentration of synthetic antiscalant up to 5 mg/L increased the efficiency, but had a small effect in higher amounts. Increasing the pH also had an adverse effect on efficiency of the reverse osmosis system and by increasing the pH from 7 to 9, the system efficiency decreased and higher TDS scores of 265.5 mg/L and 382.5 mg/L were observed in the treated effluent output, respectively. According to ANOVA statistical analysis and Prob> F values ​​of 0.0004, the data were confirmed to be consistent. Also, a good match between the actual results and the predicted results of the software was confirmed and a logical relationship was obtained between the predicted and experimental regression coefficients.

 According to the results and by determining the optimal values of the studied parameters with a concentration of 5 mg/L antiscalants and at a pH of 7, the use of synthetic antiscalant increased the treatment efficiency using a reverse osmosis system. This material, by increasing the life of the membrane and preventing the formation of deposits on the reverse osmosis membrane, increased the time of use of this system and higher treatment efficiency was achieved in the reverse osmosis system in the presence of this anti-fouling.

Due to the existence of industries such as stainless steel, the presence of nickel (II) ions in water and wastewater has been reported at high concentrations. Removal of nickel (II) ions from wastewater and the environment are of primary importance. In this study, iron (III) oxide nanoparticles were studied as an adsorbent for removal of Ni (II) ions from water in the batch equilibrium system.

FT-IR, SEM and XRD techniques were used to characterize the structure of the sample. To determine the optimum adsorption, the effect of important parameters such as pH, contact time, adsorbent weight and initial concentration were investigated. Also, thermodynamic study (Gibbs standard energy variations, enthalpy and entropy), isothermal studies (absorption capacity) and kinetic studies (absorbent effect with time) were investigated.

The results showed that the magnetic adsorbent had the highest removal efficiency of nickel (II) at pH 7, contact time 60 min, adsorbent dosage of 200 mg, and maximum removable concentration of 400 mg/L.

With thermodynamic studies, it was determined that the reaction was endothermic and the spontaneous process was controlled using the entropy factor (ΔG°=-2.7 KJ/mol, ΔS°=+165.17 J/mol.K). In order to better understand the mechanism of adsorption, kinetics studies were carried out using the pseudo-first-order and pseudo-second-order models. Then, Langmuir and Freundlich adsorption isotherms were investigated to determine the adsorption capacity, and it was found that the adsorption data were well fitted to Freundlich model and the maximum adsorption capacity was 43.5 mg/g, which indicated high adsorption capacity and its multi-layers.Then, Langmuir and Freundlich adsorption isotherms were investigated and it was found that the adsorption data were well fitted to Freundlich model and maximum adsorption capacity (qmax=43.5 mg/g) was obtained which indicates good adsorption capacity of adsorbent and its multi-layers.

Coagulation, which is carried out by mixing coagulants such as alum, ferric chloride and poly aluminum chloride PAC with raw water, is one of the main processes in conventional water treatment plants. Sludge from this process contains high amounts of coagulants with high economic value. Therefore, if these coagulants are recovered, in addition to reducing the risks relate to sludge disposal, the expenses related to the supply of fresh coagulant in water or wastewater treatment plant may decrease. To access related documentation, ScienceDirect, Google scholar and other databases were searched using keywords such as “coagulant recovery”, “water residuals management”, etc. More than one hundred fifty documents were investigated based on the content validity and thematic relation. Gathered contents were classified and summarized under the titles of “recovery methods”, “repeated recoveries”, “recovery regarding economic aspect” and “advantages and disadvantages of methods”. Use of new methods such as combination of membrane and chemical processes or ion exchange membrane processes leads to the recovery of coagulants with a similar quality to the commercial ones. In case of using conventional and less costly methods such as acid digestion, quality of recovered coagulants is not comparable with those of commercial ones, which are used in water treatment. Different coagulants recovery methods were investigated to determine the reuse strategies. It is likely that using of recovered coagulants through conventional methods is in accordance with the related regulations of the wastewater treatment plants. Industrial use of novel processes for recovery of coagulants with higher quality needs precise technical and economical investigations.