بررسی عملکرد جاذب‌های آلی، معدنی و ترکیبی در کاهش cod پساب صنایع پتروشیمی: رویکرد مدلسازی سینتیکی

کاهش شاخص اکسیژن خواهی شیمیایی (cod) در پساب صنایع پتروشیمی به دلیل وجود ترکیبات سمی و مقاوم به تجزیه زیستی، یکی از چالش های اساسی در تصفیه پایدار پساب های صنعتی محسوب می شود. در این مطالعه، کارایی سه جاذب آلی (کربن فعال مشتق شده از پوست انار)، معدنی (نانوسیلیکا) و ترکیبی (ترکیب هر دو) در حذف cod با استفاده از روش جذب ناپیوسته در مقیاس آزمایشگاهی مورد ارزیابی قرار گرفت. پارامترهای عملیاتی شامل دوز جاذب (4 گرم بر لیتر)، زمان تماس (60 دقیقه) و ph (خنثی) بهینه سازی شدند. نتایج نشان داد که جاذب ترکیبی در شرایط بهینه با راندمان حذف 48 درصد cod، عملکرد بهتری نسبت به جاذب های منفرد دارد. همچنین، داده های سینتیکی جذب با مدل شبه مرتبه اولr²=0.94 بهتر تطابق داشتند که حاکی از مکانیسم جذب فیزیکوشیمیایی است. با توجه به سازگاری جاذب ترکیبی با مدل ایزوترم ایلوویچ و راندمان قابل توجه آن، این جاذب می تواند به عنوان گزینه ای موثر و امیدوارکننده در تصفیه پساب های پیچیده پتروشیمی مورد استفاده قرار گیرد.

evaluation of organic, inorganic, and hybrid adsorbents for cod reduction in petrochemical wastewater: a kinetic modeling approach

introductionpetrochemical industries represent one of the primary sources of industrial wastewater, containing complex and hazardous compounds such as aromatic hydrocarbons, phenols, and heavy metals, with chemical oxygen demand (cod) typically ranging from 500 to 74,800 mg/l. these pollutants not only pose a severe threat to aquatic ecosystems but also render conventional treatment methods like sedimentation and filtration ineffective. in recent years, adsorption has emerged as a promising technique due to its operational cost-effectiveness, flexibility, and environmental compatibility. however, selecting an appropriate adsorbent based on wastewater physicochemical characteristics and operational conditions remains a critical challenge. this study aims to evaluate the performance of organic (pomegranate peel-derived activated carbon), inorganic (nanosilica), and hybrid adsorbents in reducing cod from petrochemical wastewater, coupled with kinetic modeling of the adsorption process.materials and methodsin this study, organic adsorbents were prepared from pomegranate peels activated with 98% sulfuric acid, while inorganic adsorbents (nanosilica, ≥99.3% purity) were procured from merck. the hybrid adsorbent was synthesized at a 1:1 ratio of organic to inorganic components. adsorbent characteristics were determined using bet and edx analyses, revealing specific surface areas of 748 m²/g for the organic adsorbent and 140 m²/g for the nanosilica. batch adsorption experiments were conducted at laboratory scale with adsorbent doses of 2 and 4 g/l, contact times of 20, 40, and 60 minutes, and neutral ph (7.0). key parameters including cod, turbidity, nitrate, sulfide, tss, and tds were measured following astm standard methods. data were analyzed using sas software and anova. three kinetic models—pseudo-first-order, pseudo-second-order, and elovich—were employed to elucidate the adsorption mechanism.results and discussionthe hybrid adsorbent ca4 demonstrated superior performance with 48% cod removal efficiency, attributed to the synergistic effects of the organic component (high adsorption capacity) and inorganic component (structural stability). increasing contact time from 20 to 60 minutes enhanced removal efficiency by 1.5-fold. the pseudo-first-order kinetic model (r² = 0.94) exhibited the best fit with experimental data, suggesting a physiochemical adsorption mechanism. ph studies revealed neutral conditions (ph 7) as optimal due to minimized ionic competition and adsorbent stability, while acidic (h₃o⁺ competition) and alkaline (oh⁻ electrostatic repulsion) environments reduced efficiency. edx analysis confirmed the critical roles of silicon (22.8%) in the inorganic adsorbent and carbon (72.3%) in the organic adsorbent. comparative analysis indicated that the hybrid ca4, despite its low production cost, achieved comparable performance to commercial activated carbon.conclusionthis study highlights the hybrid adsorbent ca4 as a viable solution for petrochemical wastewater treatment, achieving 48% cod removal under optimized conditions (ph 7, 60 minutes, 4 g/l). the use of waste-derived materials (pomegranate peels) significantly reduced production costs, while the adsorbent retained 80% of its initial efficiency after five regeneration cycles, underscoring its economic feasibility for industrial applications. limitations include variability in adsorbent physicochemical properties and the need for comprehensive economic-environmental assessments. future research should focus on nanostructural optimization, temperature/salinity effects, and functional group modifications to enhance performance. integrating ca4 with advanced processes like fenton oxidation could further improve compliance with discharge standards.