Kinetics and Isotherm Modeling for the Treatment of Rubber Processing Effluent Using Iron (II) Sulphate Waste as a Coagulant

Application of xanthan gum as coagulant-aid for decolorization of synthetic Congo red wastewater

In recent years, utilization of polysaccharides as natural coagulant and coagulant-aid has become a topic of interest, due to the nature of biopolymers that are renewable, biodegradable, and non-toxic. In this study, Congo red, as a model dye substance, was treated using polyaluminium chloride (PAC) as the main coagulant and xanthan gum as the coagulant aid. For this purpose, the effect of pH (3-9), xanthan gum dose (0.5-4 mg/L), and the initial concentration of Congo red dye (50-100 mg/L) to the dye removal and sludge volume were investigated. The outcome of this investigation indicates that the best pH for Congo red coagulation occurred at pH 3, due to the charge neutralization mechanism. The addition of coagulant-aid dose increases the %-removal and sludge volume until reaching the best coagulant-aid dose of 2 mg/L that results in a %-removal value of 93.81% and a sludge volume of 23.5 mL/L. Further addition of xanthan gum reduced the %-removal and sludge volume due to the inter-polymer force causing more difficult floc formation. The best initial concentration of dye occurred at a Congo red concentration of 50 mg/L, with a %-removal value of 93.81% with PAC (15 mg/L) and xanthan gum (2 mg/L) coagulants. This value is considerably higher than PAC and xanthan gum only which amounts to 81.16 and 7.18%, respectively. Based on these results, it is apparent that xanthan gum can positively contribute to dye coagulation while reducing the use of harmful inorganic coagulant.

Coupling of carboxymethyl starch with 2-carboxyethyl acrylate: A new sorbent for the wastewater remediation of methylene blue

Textile and printing industries play a vital role in the economy of any country. But the effluents of these industries, which contain toxic Methylene Blue (MB) dye when mixed with fresh water, make it unfit for human health and aquatic life. For the removal of MB, different adsorbents were used, but they were expensive, non-biodegradable or less effective. In this research, novel carboxymethyl starch grafted poly 2-carboxyethyl acrylate (CM-St-g-P2CEtA) was synthesized by reacting carboxymethyl starch with 2-carboxyethyl acrylate. The reaction followed a free radical polymerization mechanism. The structure and properties of CM-St-g-P2CEtA were investigated by advanced analytical techniques. The CM-St-g-P2CEtA was employed for the remediation of Methylene Blue (MB) dye from wastewater. The removal percentage (%R) of MB was checked under different parameters, like different pH levels, different initial concentrations of dye, different adsorbent doses, and different contact times. The results obtained during the experiment were subjected to different adsorption and kinetic models. In the kinetic investigation, the experimental results were best represented by the pseudo-second-order kinetic model due to its high R² value of 0.999. Similarly, with a regression coefficient (R²) value of 0.947, the Langmuir adsorption isotherm was best represented by the experimental results. The Langmuir adsorption model showed that MB dye was adsorbed on the surface of CM-St-g-P2CEtA in a monolayer pattern. The pseudo 2nd order kinetic model suggested that the adsorption process favored chemisorption mechanism. The CM-St-g-P2CEtA showed maximum percentage removal efficiency (%R) of 99.3% for MB dye.

Ferrous Industrial Wastes-Valuable Resources for Water and Wastewater Decontamination

Ferrous waste by-products from the metallurgical industry have a high potential for valorization in the context of the circular economy, and can be converted to value-added products used in environmental remediation. This research reviews the latest data available in the literature with a focus on: (i) sources from which these types of iron-based wastes originate; (ii) the types of ferrous compounds that result from different industries; (iii) the different methods (with respect to the circular economy) used to convert them into products applied in water and wastewater decontamination; (iv) the harmful effects ferrous wastes can have on the environment and human health; and (v) the future perspectives for these types of waste.

Unified, simple and decentralized treatment process for synthetic and real-time dye contaminated wastewaters

The aim of this study is to develop a simple, economical and effective treatment scheme to treat effluents from small scale textile dyeing units and tanneries, which have been set up in rural areas. The physicochemical properties of real time effluents procured from these industries were analysed. The workflow required for treating these effluents were ascertained by preliminary tests carried out on synthetically created solutions. A novel treatment scheme for tannery and textile dye effluents sludge volume reduction by the use of sodium hypochlorite was identified. Effective methods for the safe disposal and recycling of all the by-products generated from different steps were discussed. The proposed scheme was successfully able to decolourize and detoxify both the tannery and textile dyeing effluent with over 90% removal of both COD and BOD. The impacts of the treatment scheme on 14 different effluent parameters were reported. The methodology developed in this study may be utilized to construct simple localized treatment units for handling effluents in isolated rural areas. This preliminary treatment at the source, will help in the reduction of the load on the local treatment plants and prevent their choking.

Environmental Remediation Potential of Ferrous Sulfate Waste as an Eco-Friendly Coagulant for the Removal of NH3-N and COD from the Rubber Processing Effluent

The present study was conducted to determine the potential of utilizing the FeSO₄·7H₂O waste from the titanium manufacturing industry as an effective coagulant for treating industrial effluent. In this study, the secondary rubber processing effluent (SRPE) was treated using ferrous sulfate (FeSO₄·7H₂O) waste from the titanium oxide manufacturing industry. The FeSO₄·7H₂O waste coagulation efficiency was evaluated on the elimination of ammoniacal nitrogen (NH₃-N) and chemical oxygen demand (COD) from SRPE. The central composite design (CCD) of experiments was employed to design the coagulation experiments with varying coagulation time, coagulant doses, and temperature. The coagulation experiments were optimized on the optimal elimination of NH₃-N and COD using response surface methodology (RSM). Results showed that coagulant doses and temperature significantly influenced NH₃-N and COD elimination from SRPE. The highest NH₃-N and COD removal obtained were 98.19% and 93.86%, respectively, at the optimized coagulation experimental conditions of coagulation time 70 min, coagulant doses 900 mg/L, and temperature 62 °C. The residual NH₃-N and COD in treated SPRE were found below the specified industrial effluent discharge limits set by DoE, Malaysia. Additionally, the sludge generated after coagulation of SRPE contains essential plant nutrients. The present study's finding showed that FeSO₄·7H₂O waste generated as an industrial byproduct in a titanium oxide manufacturing industry could be utilized as an eco-friendly coagulant in treating industrial effluent.

Isolation and Characterization of Magnetic Oil Palm Empty Fruits Bunch Cellulose Nanofiber Composite as a Bio-Sorbent for Cu(II) and Cr(VI) Removal

In the present study, magnetic oil palm empty fruits bunch cellulose nanofiber (M-OPEFB-CNF) composite was isolated by sol-gel method using cellulose nanofiber (CNF) obtained from oil palm empty fruits bunch (OPEFB) and Fe₃O₄ as magnetite. Several analytical methods were utilized to characterize the mechanical, chemical, thermal, and morphological properties of the isolated CNF and M-OPEFB-CNF. Subsequently, the isolated M-OPEFB-CNF composite was utilized for the adsorption of Cr(VI) and Cu(II) from aqueous solution with varying parameters, such as pH, adsorbent doses, treatment time, and temperature. Results showed that the M-OPEFB-CNF as an effective bio-sorbent for the removal of Cu(II) and Cr(VI) from aqueous solution. The adsorption isotherm modeling revealed that the Freundlich equation better describes the adsorption of Cu(II) and Cr(VI) on M-OPEFB-CNF composite. The kinetics studies revealed the pseudo-second-order kinetics model was a better-described kinetics model for the removal of Cu(II) and Cr(VI) using M-OPEFB-CNF composite as bio-sorbent. The findings of the present study showed that the M-OPEFB-CNF composite has the potential to be utilized as a bio-sorbent for heavy metals removal.

Treatment of Palm Oil Refinery Effluent Using Tannin as a Polymeric Coagulant: Isotherm, Kinetics, and Thermodynamics Analyses

The refining of the crude palm oil (CPO) generates the palm oil refinery effluent (PORE). The presence of high contents of biochemical oxygen demand (BOD), chemical oxygen demand (COD), turbidity, and suspended solids (SS) in PORE encourages the determination of an effective treatment process to minimize the environmental pollution and preserve aquatic life. In the present study, a biodegradable natural polymer, namely tannin, was utilized as a coagulant to treat PORE. The coagulation experiment was conducted using a jar test apparatus. The tannin coagulation efficiency was evaluated based on the BOD, COD, turbidity, and SS removal from PORE by varying the tannin dose (50-300 mg/L), pH (pH 4-10), treatment time (15-90 min), and sedimentation time (15-90 min). It was found that the maximum removal of BOD, COD, turbidity, and SS was 97.62%, 88.89%, 93.01%, and 90.21%, respectively, at pH 6, a tannin dose of 200 mg/L, 60 min of coagulation time, and 60 min of sedimentation time. Analyses of isotherm models revealed that the Freundlich isotherm model was well fitted with the coagulation study. Kinetics studies show that the pseudo-second-order kinetics model was the well-fitted kinetics model for the BOD, COD, turbidity, and SS removal from PORE using tannin as a polymeric coagulant. The determination of thermodynamics parameters analyses revealed that BOD, COD, turbidity, and SS removal from PORE was spontaneous, exothermic, and chemical in nature. The finding of the present study shows that tannin as a natural polymeric coagulant would be utilized in PORE treatment to avoid toxic sludge generation.